diff --git a/README.md b/README.md
index 35a7f5460..95a4dc16e 100644
--- a/README.md
+++ b/README.md
@@ -34,17 +34,14 @@ cosmocc --update   # pull cosmo and rebuild toolchain
 ```
 
 You've now successfully installed your very own cosmos. Now let's build
-an example program, which demonstrates the crash reporting feature:
+an example program:
 
 ```c
 // hello.c
 #include <stdio.h>
-#include <cosmo.h>
 
 int main() {
-  ShowCrashReports();
   printf("hello world\n");
-  __builtin_trap();
 }
 ```
 
diff --git a/libc/calls/__sig2.c b/libc/calls/__sig2.c
index 2b0fcb23e..a7873c2f6 100644
--- a/libc/calls/__sig2.c
+++ b/libc/calls/__sig2.c
@@ -181,13 +181,14 @@ textwindows bool __sig_handle(int sigops, int sig, int si_code,
   switch (__sighandrvas[sig]) {
     case (intptr_t)SIG_DFL:
       if (__sig_is_fatal(sig)) {
-        size_t len;
-        char name[16];
-        strsignal_r(sig, name);
-        len = strlen(name);
-        name[len++] = '\n';
-        WriteFile(GetStdHandle(kNtStdErrorHandle), name, len, 0, 0);
-        STRACE("terminating on %s", name);
+        intptr_t hStderr;
+        const char *signame;
+        char *end, sigbuf[15], output[16];
+        signame = strsignal_r(sig, sigbuf);
+        STRACE("terminating due to uncaught %s", signame);
+        hStderr = GetStdHandle(kNtStdErrorHandle);
+        end = stpcpy(stpcpy(output, signame), "\n");
+        WriteFile(hStderr, output, end - output, 0, 0);
         if (_weaken(__restore_console_win32)) {
           _weaken(__restore_console_win32)();
         }
diff --git a/libc/calls/calls.h b/libc/calls/calls.h
index 9fa9f03ce..e81f9def6 100644
--- a/libc/calls/calls.h
+++ b/libc/calls/calls.h
@@ -193,6 +193,7 @@ unsigned geteuid(void) nosideeffect;
 unsigned getgid(void) nosideeffect;
 unsigned getuid(void) libcesque;
 unsigned sleep(unsigned);
+unsigned ualarm(unsigned, unsigned);
 unsigned umask(unsigned);
 void sync(void);
 
diff --git a/libc/calls/createfileflags.c b/libc/calls/createfileflags.c
index 297a2ffc8..70acc7219 100644
--- a/libc/calls/createfileflags.c
+++ b/libc/calls/createfileflags.c
@@ -35,7 +35,7 @@
 #define _O_DIRECTORY  0x00010000  // kNtFileFlagBackupSemantics
 #define _O_TMPFILE    0x00410000  // AttributeTemporary|FlagDeleteOnClose
 #define _O_DIRECT     0x00004000  // kNtFileFlagNoBuffering
-#define _O_NONBLOCK   0x00000800  // kNtFileFlagWriteThrough
+#define _O_NONBLOCK   0x00000800  // kNtFileFlagWriteThrough (not sent to win32)
 #define _O_RANDOM     0x80000000  // kNtFileFlagRandomAccess
 #define _O_SEQUENTIAL 0x40000000  // kNtFileFlagSequentialScan
 #define _O_COMPRESSED 0x20000000  // kNtFileAttributeCompressed
@@ -62,16 +62,22 @@ textwindows int GetNtOpenFlags(int flags, int mode, uint32_t *out_perm,
       break;
     case O_WRONLY:
       perm = kNtFileGenericWrite;
+      if (flags & _O_APPEND) {
+        // kNtFileAppendData is already present in kNtFileGenericWrite.
+        // WIN32 wont act on append access when write is already there.
+        perm = kNtFileAppendData;
+      }
       break;
     case O_RDWR:
-      perm = kNtFileGenericRead | kNtFileGenericWrite;
+      if (flags & _O_APPEND) {
+        perm = kNtFileGenericRead | kNtFileAppendData;
+      } else {
+        perm = kNtFileGenericRead | kNtFileGenericWrite;
+      }
       break;
     default:
       return einval();
   }
-  if (flags & _O_APPEND) {
-    perm = kNtFileAppendData;  // todo: this is part of generic write above
-  }
 
   attr = 0;
   is_creating_file = (flags & _O_CREAT) || (flags & _O_TMPFILE) == _O_TMPFILE;
diff --git a/libc/calls/fchmodat-nt.c b/libc/calls/fchmodat-nt.c
index ee9966a9f..2e52eede7 100644
--- a/libc/calls/fchmodat-nt.c
+++ b/libc/calls/fchmodat-nt.c
@@ -26,7 +26,7 @@ textwindows int sys_fchmodat_nt(int dirfd, const char *path, uint32_t mode,
   uint16_t path16[PATH_MAX];
   if (__mkntpathat(dirfd, path, 0, path16) == -1) return -1;
   if ((attr = GetFileAttributes(path16)) != -1u) {
-    if (mode & 0200) {
+    if (mode & 0222) {
       attr &= ~kNtFileAttributeReadonly;
     } else {
       attr |= kNtFileAttributeReadonly;
diff --git a/libc/calls/fcntl-nt.c b/libc/calls/fcntl-nt.c
index 3866824ce..a0df32741 100644
--- a/libc/calls/fcntl-nt.c
+++ b/libc/calls/fcntl-nt.c
@@ -26,10 +26,13 @@
 #include "libc/calls/wincrash.internal.h"
 #include "libc/errno.h"
 #include "libc/intrin/kmalloc.h"
+#include "libc/intrin/kprintf.h"
 #include "libc/intrin/weaken.h"
 #include "libc/limits.h"
 #include "libc/log/backtrace.internal.h"
 #include "libc/macros.internal.h"
+#include "libc/nt/createfile.h"
+#include "libc/nt/enum/fileflagandattributes.h"
 #include "libc/nt/enum/filelockflags.h"
 #include "libc/nt/errors.h"
 #include "libc/nt/files.h"
@@ -310,52 +313,63 @@ static textwindows int sys_fcntl_nt_dupfd(int fd, int cmd, int start) {
   return sys_dup_nt(fd, -1, (cmd == F_DUPFD_CLOEXEC ? O_CLOEXEC : 0), start);
 }
 
-static textwindows int sys_fcntl_nt_setfl(int fd, unsigned *flags, unsigned arg,
-                                          unsigned supported) {
-  unsigned old, neu, changed, other, allowed;
-  old = *flags & supported;
-  other = *flags & ~supported;
-  neu = arg & supported;
-  changed = old ^ neu;
-  // you may change the following access mode flags:
+static textwindows int sys_fcntl_nt_setfl(int fd, unsigned *flags,
+                                          unsigned mode, unsigned arg,
+                                          intptr_t *handle) {
+
+  // you may change the following:
   //
   // - O_NONBLOCK     make read() raise EAGAIN
-  // - O_NDELAY       same thing as O_NONBLOCK
-  // - O_ACCMODE      but has a minimal effect
+  // - O_APPEND       for toggling append mode
+  // - O_RANDOM       alt. for posix_fadvise()
+  // - O_SEQUENTIAL   alt. for posix_fadvise()
+  // - O_DIRECT       works but haven't tested
   //
-  allowed = O_ACCMODE | O_NONBLOCK;
-  if (changed & ~allowed) {
-    // the following access mode flags are supported, but it's currently
-    // not possible to change them on windows.
-    //
-    // - O_APPEND     tried to support but failed
-    // - O_RANDOM     use posix_fadvise() instead
-    // - O_SEQUENTIAL use posix_fadvise() instead
-    // - O_DIRECT     possibly in future?
-    // - O_DSYNC      possibly in future?
-    // - O_RSYNC      possibly in future?
-    // - O_SYNC       possibly in future?
-    //
-    return enotsup();
+  // the other bits are ignored.
+  unsigned allowed = O_APPEND | O_SEQUENTIAL | O_RANDOM | O_DIRECT | O_NONBLOCK;
+  unsigned needreo = O_APPEND | O_SEQUENTIAL | O_RANDOM | O_DIRECT;
+  unsigned newflag = (*flags & ~allowed) | (arg & allowed);
+
+  if ((*flags & needreo) ^ (arg & needreo)) {
+    unsigned perm, share, attr;
+    if (GetNtOpenFlags(newflag, mode, &perm, &share, 0, &attr) == -1) {
+      return -1;
+    }
+    // MSDN says only these are allowed, otherwise it returns EINVAL.
+    attr &= kNtFileFlagBackupSemantics | kNtFileFlagDeleteOnClose |
+            kNtFileFlagNoBuffering | kNtFileFlagOpenNoRecall |
+            kNtFileFlagOpenReparsePoint | kNtFileFlagOverlapped |
+            kNtFileFlagPosixSemantics | kNtFileFlagRandomAccess |
+            kNtFileFlagSequentialScan | kNtFileFlagWriteThrough;
+    intptr_t hand;
+    if ((hand = ReOpenFile(*handle, perm, share, attr)) != -1) {
+      if (hand != *handle) {
+        CloseHandle(*handle);
+        *handle = hand;
+      }
+    } else {
+      return __winerr();
+    }
   }
+
   // 1. ignore flags that aren't access mode flags
   // 2. return zero if nothing's changed
-  *flags = other | neu;
+  *flags = newflag;
   return 0;
 }
 
 textwindows int sys_fcntl_nt(int fd, int cmd, uintptr_t arg) {
   int rc;
   uint32_t flags;
-  int access_mode_flags = O_ACCMODE | O_APPEND | O_ASYNC | O_DIRECT |
-                          O_NOATIME | O_NONBLOCK | O_RANDOM | O_SEQUENTIAL;
   if (__isfdkind(fd, kFdFile) ||    //
       __isfdkind(fd, kFdSocket) ||  //
       __isfdkind(fd, kFdConsole)) {
     if (cmd == F_GETFL) {
-      rc = g_fds.p[fd].flags & access_mode_flags;
+      rc = g_fds.p[fd].flags & (O_ACCMODE | O_APPEND | O_DIRECT | O_NONBLOCK |
+                                O_RANDOM | O_SEQUENTIAL);
     } else if (cmd == F_SETFL) {
-      rc = sys_fcntl_nt_setfl(fd, &g_fds.p[fd].flags, arg, access_mode_flags);
+      rc = sys_fcntl_nt_setfl(fd, &g_fds.p[fd].flags, g_fds.p[fd].mode, arg,
+                              &g_fds.p[fd].handle);
     } else if (cmd == F_GETFD) {
       if (g_fds.p[fd].flags & O_CLOEXEC) {
         rc = FD_CLOEXEC;
diff --git a/libc/calls/fcntl.c b/libc/calls/fcntl.c
index 9cd24dce1..915040a30 100644
--- a/libc/calls/fcntl.c
+++ b/libc/calls/fcntl.c
@@ -27,9 +27,9 @@
 #include "libc/intrin/describeflags.internal.h"
 #include "libc/intrin/strace.internal.h"
 #include "libc/intrin/weaken.h"
+#include "libc/runtime/zipos.internal.h"
 #include "libc/sysv/consts/f.h"
 #include "libc/sysv/errfuns.h"
-#include "libc/runtime/zipos.internal.h"
 
 /**
  * Does things with file descriptor, e.g.
@@ -57,6 +57,12 @@
  *     - `F_SETFD` sets `FD_CLOEXEC` status of `arg` file descriptor
  *     - `F_GETFL` returns file descriptor status flags
  *     - `F_SETFL` sets file descriptor status flags
+ *       - `O_NONBLOCK` may be changed
+ *       - `O_APPEND` may be changed
+ *       - `O_DIRECT` may be changed
+ *       - `O_SEQUENTIAL` may be changed (no-op on non-Windows)
+ *       - `O_RANDOM` may be changed (no-op on non-Windows)
+ *       - Other bits (`O_ACCMODE`, `O_CREAT`, etc.) are ignored
  *     - `F_DUPFD` is like dup() but `arg` is a minimum result, e.g. 3
  *     - `F_DUPFD_CLOEXEC` ditto but sets `O_CLOEXEC` on returned fd
  *     - `F_SETLK` for record locking where `arg` is `struct flock *`
@@ -131,11 +137,15 @@ int fcntl(int fd, int cmd, ...) {
   }
 
 #ifdef SYSDEBUG
-  if (cmd == F_GETFD ||         //
-      cmd == F_GETOWN ||        //
-      cmd == F_FULLFSYNC ||     //
-      cmd == F_BARRIERFSYNC ||  //
-      cmd == F_MAXFD) {
+  if (rc != -1 && cmd == F_GETFL) {
+    STRACE("fcntl(%d, F_GETFL) → %s", fd, DescribeOpenFlags(rc));
+  } else if (cmd == F_SETFL) {
+    STRACE("fcntl(%d, F_SETFL, %s) → %d% m", fd, DescribeOpenFlags(arg), rc);
+  } else if (cmd == F_GETFD ||         //
+             cmd == F_GETOWN ||        //
+             cmd == F_FULLFSYNC ||     //
+             cmd == F_BARRIERFSYNC ||  //
+             cmd == F_MAXFD) {
     STRACE("fcntl(%d, %s) → %d% m", fd, DescribeFcntlCmd(cmd), rc);
   } else if (cmd == F_GETFL) {
     STRACE("fcntl(%d, %s) → %s% m", fd, DescribeFcntlCmd(cmd),
diff --git a/libc/calls/fstatat.c b/libc/calls/fstatat.c
index fe5262bca..2a0b6ddfa 100644
--- a/libc/calls/fstatat.c
+++ b/libc/calls/fstatat.c
@@ -52,27 +52,31 @@ static inline const char *__strace_fstatat_flags(char buf[12], int flags) {
  *     file is a relative path, then `path` becomes relative to `dirfd`
  * @param st is where the result is stored
  * @param flags can have `AT_SYMLINK_NOFOLLOW`
- * @param st is where result is stored
  * @raise EACCES if denied access to component in path prefix
  * @raise EIO if i/o error occurred while reading from filesystem
  * @raise ELOOP if a symbolic link loop exists in `path`
  * @raise ENAMETOOLONG if a component in `path` exceeds `NAME_MAX`
  * @raise ENOENT on empty string or if component in path doesn't exist
  * @raise ENOTDIR if a parent component existed that wasn't a directory
+ * @raise EILSEQ if `path` contains illegal UTF-8 sequences (Windows/MacOS)
  * @raise ENOTDIR if `path` is relative and `dirfd` isn't an open directory
+ * @raise ENOEXEC if `path` is a zip path and this executable isn't a zip file
  * @raise EOVERFLOW shouldn't be possible on 64-bit systems
  * @raise ELOOP may ahappen if `SYMLOOP_MAX` symlinks were dereferenced
  * @raise ENAMETOOLONG may happen if `path` exceeded `PATH_MAX`
+ * @raise EFAULT if `path` or `st` point to invalid memory
+ * @raise EINVAL if `flags` has unsupported bits
  * @return 0 on success, or -1 w/ errno
  * @see S_ISDIR(st.st_mode), S_ISREG()
  * @asyncsignalsafe
  * @vforksafe
  */
 int fstatat(int dirfd, const char *path, struct stat *st, int flags) {
-  /* execve() depends on this */
+  // execve() depends on this
   int rc;
   struct ZiposUri zipname;
-  if (IsAsan() && !__asan_is_valid(st, sizeof(*st))) {
+  if (IsAsan() && (!__asan_is_valid_str(path) ||  //
+                   !__asan_is_valid(st, sizeof(*st)))) {
     rc = efault();
   } else if (flags & ~AT_SYMLINK_NOFOLLOW) {
     return einval();
diff --git a/libc/calls/ioctl.c b/libc/calls/ioctl.c
index bf40ebd0f..12f35b71d 100644
--- a/libc/calls/ioctl.c
+++ b/libc/calls/ioctl.c
@@ -596,68 +596,68 @@ static int ioctl_siocgifflags(int fd, void *arg) {
 /**
  * Performs special i/o operation on file descriptor.
  *
- * @param request can be any of:
+ * The following i/o requests are available.
  *
- *     - `FIONREAD` takes an `int *` and returns how many bytes of input
- *       are available on a terminal or socket, waiting to be read.
+ * - `FIONREAD` takes an `int *` and returns how many bytes of input are
+ *   available on a terminal/socket/pipe, waiting to be read. Be sure to
+ *   only use it on the reading end of a pipe.
  *
- *     - `TIOCGWINSZ` populates `struct winsize *` with the dimensions
- *       of your teletypewriter. It's an alias for tcgetwinsize().
+ * - `TIOCGWINSZ` populates `struct winsize *` with the dimensions of
+ *   your teletypewriter. It's an alias for tcgetwinsize().
  *
- *     - `TIOCSWINSZ` with the dimensions of your teletypewriter to
- *       `struct winsize *`. It's an alias for tcsetwinsize().
+ * - `TIOCSWINSZ` with the dimensions of your teletypewriter to `struct
+ *   winsize *`. It's an alias for tcsetwinsize().
  *
- *     - `TIOCOUTQ` takes an `int *` and returns the number of bytes in
- *       the terminal's output buffer. Only available on UNIX.
+ * - `TIOCOUTQ` takes an `int *` and returns the number of bytes in the
+ *   terminal's output buffer. Only available on UNIX.
  *
- *     - `TIOCSTI` takes a `const char *` and may be used to fake input
- *       to a tty. This API isn't available on OpenBSD. Only available
- *       on UNIX.
+ * - `TIOCSTI` takes a `const char *` and may be used to fake input to a
+ *   tty. This API isn't available on OpenBSD. Only available on UNIX.
  *
- *     - `TIOCNOTTY` takes an `int tty_fd` arg and makes it the
- *       controlling terminal of the calling process, which should have
- *       called setsid() beforehand.
+ * - `TIOCNOTTY` takes an `int tty_fd` arg and makes it the controlling
+ *   terminal of the calling process, which should have called setsid()
+ *   beforehand.
  *
- *     - `TIOCNOTTY` to give up the controlling terminal. Only available
- *       on UNIX.
+ * - `TIOCNOTTY` to give up the controlling terminal. Only available on
+ *   UNIX.
  *
- *     - `TIOCNXCL` to give up exclusive mode on terminal. Only
- *       available on UNIX.
+ * - `TIOCNXCL` to give up exclusive mode on terminal. Only available on
+ *   UNIX.
  *
- *     - `SIOCGIFCONF` takes an struct ifconf object of a given size,
- *       whose arg is `struct ifconf *`. It implements the Linux style
- *       and modifies the following:
- *       - ifc_len: set it to the number of valid ifreq structures
- *         representingthe interfaces
- *       - ifc_ifcu.ifcu_req: sets the name of the interface for each
- *         interface
- *       The ifc_len is an input/output parameter: set it to the total
- *       size of the ifcu_buf (ifcu_req) buffer on input.
+ * - `SIOCGIFCONF` takes an struct ifconf object of a given size,
+ *   whose arg is `struct ifconf *`. It implements the Linux style
+ *   and modifies the following:
+ *   - ifc_len: set it to the number of valid ifreq structures
+ *     representingthe interfaces
+ *   - ifc_ifcu.ifcu_req: sets the name of the interface for each
+ *     interface
+ *   The ifc_len is an input/output parameter: set it to the total
+ *   size of the ifcu_buf (ifcu_req) buffer on input.
  *
- *     - `SIOCGIFNETMASK` populates a `struct ifconf *` record with the
- *       network interface mask. This data structure should be obtained
- *       by calling `SIOCGIFCONF`.
+ * - `SIOCGIFNETMASK` populates a `struct ifconf *` record with the
+ *   network interface mask. This data structure should be obtained by
+ *   calling `SIOCGIFCONF`.
  *
- *     - `SIOCGIFBRDADDR` populates a `struct ifconf *` record with the
- *       network broadcast addr. This data structure should be obtained
- *       by calling `SIOCGIFCONF`.
+ * - `SIOCGIFBRDADDR` populates a `struct ifconf *` record with the
+ *   network broadcast addr. This data structure should be obtained by
+ *   calling `SIOCGIFCONF`.
  *
- *     - `FIONBIO` isn't polyfilled; use `fcntl(F_SETFL, O_NONBLOCK)`
- *     - `FIOCLEX` isn't polyfilled; use `fcntl(F_SETFD, FD_CLOEXEC)`
- *     - `FIONCLEX` isn't polyfilled; use `fcntl(F_SETFD, 0)`
- *     - `TCGETS` isn't polyfilled; use tcgetattr()
- *     - `TCSETS` isn't polyfilled; use tcsetattr()
- *     - `TCSETSW` isn't polyfilled; use tcsetattr()
- *     - `TCSETSF` isn't polyfilled; use tcsetattr()
- *     - `TCXONC` isn't polyfilled; use tcflow()
- *     - `TCSBRK` isn't polyfilled; use tcdrain()
- *     - `TCFLSH` isn't polyfilled; use tcflush()
- *     - `TIOCGPTN` isn't polyfilled; use ptsname()
- *     - `TIOCGSID` isn't polyfilled; use tcgetsid()
- *     - `TCSBRK` isn't polyfilled; use tcsendbreak()
- *     - `TCSBRK` isn't polyfilled; use tcsendbreak()
- *     - `TIOCSPGRP` isn't polyfilled; use tcsetpgrp()
- *     - `TIOCSPTLCK` isn't polyfilled; use unlockpt()
+ * - `FIONBIO` isn't polyfilled; use `fcntl(F_SETFL, O_NONBLOCK)`
+ * - `FIOCLEX` isn't polyfilled; use `fcntl(F_SETFD, FD_CLOEXEC)`
+ * - `FIONCLEX` isn't polyfilled; use `fcntl(F_SETFD, 0)`
+ * - `TCGETS` isn't polyfilled; use tcgetattr()
+ * - `TCSETS` isn't polyfilled; use tcsetattr()
+ * - `TCSETSW` isn't polyfilled; use tcsetattr()
+ * - `TCSETSF` isn't polyfilled; use tcsetattr()
+ * - `TCXONC` isn't polyfilled; use tcflow()
+ * - `TCSBRK` isn't polyfilled; use tcdrain()
+ * - `TCFLSH` isn't polyfilled; use tcflush()
+ * - `TIOCGPTN` isn't polyfilled; use ptsname()
+ * - `TIOCGSID` isn't polyfilled; use tcgetsid()
+ * - `TCSBRK` isn't polyfilled; use tcsendbreak()
+ * - `TCSBRK` isn't polyfilled; use tcsendbreak()
+ * - `TIOCSPGRP` isn't polyfilled; use tcsetpgrp()
+ * - `TIOCSPTLCK` isn't polyfilled; use unlockpt()
  *
  * @restartable
  * @vforksafe
diff --git a/libc/calls/mkdirat-nt.c b/libc/calls/mkdirat-nt.c
index 5faa232e8..ff80df40f 100644
--- a/libc/calls/mkdirat-nt.c
+++ b/libc/calls/mkdirat-nt.c
@@ -16,15 +16,12 @@
 │ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/calls/syscall-nt.internal.h"
 #include "libc/calls/syscall_support-nt.internal.h"
 #include "libc/nt/files.h"
-#include "libc/str/str.h"
-#include "libc/sysv/errfuns.h"
 
 textwindows int sys_mkdirat_nt(int dirfd, const char *path, uint32_t mode) {
-  int e;
-  char16_t *p, path16[PATH_MAX];
-  /* if (strlen(path) > 248) return enametoolong(); */
+  char16_t path16[PATH_MAX];
   if (__mkntpathat(dirfd, path, 0, path16) == -1) return -1;
   if (CreateDirectory(path16, 0)) return 0;
   return __fix_enotdir(-1, path16);
diff --git a/libc/calls/mkntpath.c b/libc/calls/mkntpath.c
index 17d5dbe17..3948cafb8 100644
--- a/libc/calls/mkntpath.c
+++ b/libc/calls/mkntpath.c
@@ -18,6 +18,8 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/calls/ntmagicpaths.internal.h"
 #include "libc/calls/syscall_support-nt.internal.h"
+#include "libc/dce.h"
+#include "libc/intrin/asan.internal.h"
 #include "libc/intrin/strace.internal.h"
 #include "libc/macros.internal.h"
 #include "libc/nt/systeminfo.h"
@@ -75,22 +77,21 @@ textwindows int __mkntpath(const char *path,
  */
 textwindows int __mkntpath2(const char *path,
                             char16_t path16[hasatleast PATH_MAX], int flags) {
-  /*
-   * 1. Need +1 for NUL-terminator
-   * 2. Need +1 for UTF-16 overflow
-   * 3. Need ≥2 for SetCurrentDirectory trailing slash requirement
-   * 4. Need ≥13 for mkdir() i.e. 1+8+3+1, e.g. "\\ffffffff.xxx\0"
-   *    which is an "8.3 filename" from the DOS days
-   */
-  const char *q;
-  bool isdospath;
-  char16_t c, *p;
-  size_t i, j, n, m, x, z;
-  if (!path) return efault();
-  path = FixNtMagicPath(path, flags);
-  p = path16;
-  q = path;
 
+  // 1. Need +1 for NUL-terminator
+  // 2. Need +1 for UTF-16 overflow
+  // 3. Need ≥2 for SetCurrentDirectory trailing slash requirement
+  // 4. Need ≥13 for mkdir() i.e. 1+8+3+1, e.g. "\\ffffffff.xxx\0"
+  //    which is an "8.3 filename" from the DOS days
+
+  if (!path || (IsAsan() && !__asan_is_valid_str(path))) {
+    return efault();
+  }
+  path = FixNtMagicPath(path, flags);
+
+  size_t x, z;
+  char16_t *p = path16;
+  const char *q = path;
   if (IsSlash(q[0]) && IsAlpha(q[1]) && IsSlash(q[2])) {
     z = MIN(32767, PATH_MAX);
     // turn "\c\foo" into "\\?\c:\foo"
@@ -142,6 +143,7 @@ textwindows int __mkntpath2(const char *path,
   }
 
   // turn /tmp into GetTempPath()
+  size_t m;
   if (!x && IsSlash(q[0]) && q[1] == 't' && q[2] == 'm' && q[3] == 'p' &&
       (IsSlash(q[4]) || !q[4])) {
     m = GetTempPath(z, p);
@@ -154,23 +156,37 @@ textwindows int __mkntpath2(const char *path,
   }
 
   // turn utf-8 into utf-16
-  n = tprecode8to16(p, z, q).ax;
+  size_t n = tprecode8to16(p, z, q).ax;
   if (n >= z - 1) {
-    STRACE("path too long for windows: %#s", path);
     return enametoolong();
   }
 
-  // 1. turn `/` into `\`
-  // 2. turn `\\` into `\` if not at beginning
+  // normalize path
+  // we need it because \\?\... paths have to be normalized
+  // we don't remove the trailing slash since it is special
+  size_t i, j;
   for (j = i = 0; i < n; ++i) {
-    c = p[i];
+    int c = p[i];
     if (c == '/') {
       c = '\\';
     }
     if (j > 1 && c == '\\' && p[j - 1] == '\\') {
-      continue;
+      // matched "^/" or "//" but not "^//"
+    } else if ((j && p[j - 1] == '\\') &&  //
+               c == '.' &&                 //
+               (i + 1 == n || IsSlash(p[i + 1]))) {
+      // matched "/./" or "/.$"
+      i += !(i + 1 == n);
+    } else if ((j && p[j - 1] == '\\') &&         //
+               c == '.' &&                        //
+               (i + 1 < n && p[i + 1] == '.') &&  //
+               (i + 2 == n || IsSlash(p[i + 2]))) {
+      // matched "/../" or "/..$"
+      while (j && p[j - 1] == '\\') --j;
+      while (j && p[j - 1] != '\\') --j;
+    } else {
+      p[j++] = c;
     }
-    p[j++] = c;
   }
   p[j] = 0;
   n = j;
@@ -180,11 +196,11 @@ textwindows int __mkntpath2(const char *path,
 
   // To avoid toil like this:
   //
-  //     CMD.EXE was started with the above path as the current directory.
-  //     UNC paths are not supported.  Defaulting to Windows directory.
-  //     Access is denied.
+  //     "CMD.EXE was started with the above path as the current
+  //      directory. UNC paths are not supported. Defaulting to Windows
+  //      directory. Access is denied." -Quoth CMD.EXE
   //
-  // Remove \\?\ prefix if we're within 260 character limit.
+  // Remove \\?\ prefix if we're within the 260 character limit.
   if (n > 4 && n < 260 &&   //
       path16[0] == '\\' &&  //
       path16[1] == '\\' &&  //
@@ -194,10 +210,5 @@ textwindows int __mkntpath2(const char *path,
     n -= 4;
   }
 
-  // turn "foo\\." into "foo\\"
-  if (n > 2 && path16[n - 1] == u'.' && path16[n - 2] == u'\\') {
-    path16[--n] = 0;
-  }
-
   return n;
 }
diff --git a/libc/calls/mkntpathat.c b/libc/calls/mkntpathat.c
index 5bdf76c32..098320181 100644
--- a/libc/calls/mkntpathat.c
+++ b/libc/calls/mkntpathat.c
@@ -29,9 +29,10 @@ int __mkntpathat(int dirfd, const char *path, int flags,
                  char16_t file[hasatleast PATH_MAX]) {
   char16_t dir[PATH_MAX];
   uint32_t dirlen, filelen;
+  if (!isutf8(path, -1)) return eilseq();  // thwart overlong nul in conversion
   if ((filelen = __mkntpath2(path, file, flags)) == -1) return -1;
   if (!filelen) return enoent();
-  if (file[0] != u'\\' && dirfd != AT_FDCWD) { /* ProTip: \\?\C:\foo */
+  if (file[0] != u'\\' && dirfd != AT_FDCWD) {  // ProTip: \\?\C:\foo
     if (!__isfdkind(dirfd, kFdFile)) return ebadf();
     dirlen = GetFinalPathNameByHandle(g_fds.p[dirfd].handle, dir, ARRAYLEN(dir),
                                       kNtFileNameNormalized | kNtVolumeNameDos);
diff --git a/libc/calls/open-nt.c b/libc/calls/open-nt.c
index 72d6c13bf..f30469b0f 100644
--- a/libc/calls/open-nt.c
+++ b/libc/calls/open-nt.c
@@ -22,34 +22,92 @@
 #include "libc/calls/state.internal.h"
 #include "libc/calls/syscall-nt.internal.h"
 #include "libc/calls/syscall_support-nt.internal.h"
+#include "libc/errno.h"
+#include "libc/intrin/kprintf.h"
 #include "libc/nt/createfile.h"
+#include "libc/nt/enum/creationdisposition.h"
 #include "libc/nt/enum/fileflagandattributes.h"
 #include "libc/nt/enum/filetype.h"
 #include "libc/nt/files.h"
+#include "libc/nt/process.h"
 #include "libc/nt/runtime.h"
+#include "libc/nt/thunk/msabi.h"
 #include "libc/str/str.h"
 #include "libc/sysv/consts/fileno.h"
 #include "libc/sysv/consts/o.h"
 #include "libc/sysv/errfuns.h"
 
+__msabi extern typeof(GetFileAttributes) *const __imp_GetFileAttributesW;
+
 static textwindows int64_t sys_open_nt_impl(int dirfd, const char *path,
                                             uint32_t flags, int32_t mode,
                                             uint32_t extra_attr) {
+
+  // join(topath(dirfd), path) and translate from utf-8 to utf-16
   char16_t path16[PATH_MAX];
-  uint32_t perm, share, disp, attr;
   if (__mkntpathat(dirfd, path, flags, path16) == -1) {
     return kNtInvalidHandleValue;
   }
+
+  // strip trailing slash
+  size_t n = strlen16(path16);
+  if (n > 1 && path16[n - 1] == '\\') {
+    // path denormalization only goes so far. when a trailing / or /.
+    // exists the kernel interprets that as having O_DIRECTORY intent
+    // furthermore, windows will throw an error on unc paths with it!
+    flags |= O_DIRECTORY;
+    path16[--n] = 0;
+  }
+
+  // implement no follow flag
+  // you can't open symlinks; use readlink
+  // this flag only applies to the final path component
+  // if O_NOFOLLOW_ANY is passed (-1 on NT) it'll be rejected later
+  uint32_t fattr = __imp_GetFileAttributesW(path16);
   if (flags & O_NOFOLLOW) {
-    if ((attr = GetFileAttributes(path16)) != -1u &&  //
-        (attr & kNtFileAttributeReparsePoint)) {
+    if (fattr != -1u && (fattr & kNtFileAttributeReparsePoint)) {
       return eloop();
     }
-    flags &= ~O_NOFOLLOW;
+    flags &= ~O_NOFOLLOW;  // don't actually pass this to win32
   }
+
+  // handle some obvious cases while we have the attributes
+  // we should ideally resolve symlinks ourself before doing this
+  if (fattr != -1u) {
+    if (fattr & kNtFileAttributeDirectory) {
+      if ((flags & O_ACCMODE) != O_RDONLY || (flags & O_CREAT)) {
+        // tried to open directory for writing. note that our
+        // undocumented O_TMPFILE support on windows requires that a
+        // filename be passed, rather than a directory like linux.
+        return eisdir();
+      }
+      // on posix, the o_directory flag is an advisory safeguard that
+      // isn't required. on windows, it's mandatory for opening a dir
+      flags |= O_DIRECTORY;
+    } else if (!(fattr & kNtFileAttributeReparsePoint)) {
+      // we know for certain file isn't a directory
+      if (flags & O_DIRECTORY) {
+        return enotdir();
+      }
+    }
+  }
+
+  // translate posix flags to win32 flags
+  uint32_t perm, share, disp, attr;
   if (GetNtOpenFlags(flags, mode, &perm, &share, &disp, &attr) == -1) {
     return kNtInvalidHandleValue;
   }
+
+  // kNtTruncateExisting always returns kNtErrorInvalidParameter :'(
+  if (disp == kNtTruncateExisting) {
+    if (fattr != -1u) {
+      disp = kNtCreateAlways;  // file exists (wish it could be more atomic)
+    } else {
+      return __fix_enotdir(enotdir(), path16);
+    }
+  }
+
+  // open the file, following symlinks
   return __fix_enotdir(CreateFile(path16, perm, share, &kNtIsInheritable, disp,
                                   attr | extra_attr, 0),
                        path16);
diff --git a/libc/calls/openat.c b/libc/calls/openat.c
index 903128eb7..7ee1d659c 100644
--- a/libc/calls/openat.c
+++ b/libc/calls/openat.c
@@ -24,6 +24,7 @@
 #include "libc/calls/syscall-nt.internal.h"
 #include "libc/calls/syscall-sysv.internal.h"
 #include "libc/dce.h"
+#include "libc/errno.h"
 #include "libc/intrin/asan.internal.h"
 #include "libc/intrin/describeflags.internal.h"
 #include "libc/intrin/strace.internal.h"
@@ -56,7 +57,7 @@
  *
  *     __static_yoink("zipos");
  *
- * Then you can read zip assets by adding a `"/zip/..."` prefix to `file`, e.g.
+ * Then you can read zip assets by adding a `"/zip/..."` prefix to `path`, e.g.
  *
  *     // run `zip program.com hi.txt` beforehand
  *     openat(AT_FDCWD, "/zip/hi.txt", O_RDONLY);
@@ -64,10 +65,12 @@
  * Cosmopolitan's general approach on Windows to path translation is to
  *
  *   - replace `/' with `\`
+ *   - normalize `.' and `..`
  *   - translate utf-8 into utf-16
  *   - turn `"\X\foo"` into `"\\?\X:\foo"`
  *   - turn `"\X"` into `"\\?\X:\"`
  *   - turn `"X:\foo"` into `"\\?\X:\foo"`
+ *   - turn `"\\?\X:\foo"` back into `X:\foo` if less than 260 chars
  *
  * On Windows, opening files in `/tmp` will open them in GetTempPath(),
  * which is a secure per-user directory. Opening `/dev/tty` will open a
@@ -75,31 +78,24 @@
  * which can't be fully closed. Opening `/dev/null` will open up `NUL`.
  *
  * @param dirfd is normally `AT_FDCWD` but if it's an open directory and
- *     `file` names a relative path then it's opened relative to `dirfd`
- * @param file is a UTF-8 string naming filesystem entity, e.g. `foo/bar.txt`,
- *     which on Windows is bludgeoned into a WIN32 path automatically, e.g.
- *     - `foo/bar.txt` becomes `foo\bar.txt`
- *     - `/tmp/...` becomes whatever GetTempPath() is
- *     - `\\...` or `//...` is passed through to WIN32 unchanged
- *     - `/c/foo` or `\c\foo` becomes `\\?\c:\foo`
- *     - `c:/foo` or `c:\foo` becomes `\\?\c:\foo`
- *     - `/D` becomes `\\?\D:\`
+ *     `path` names a relative path then it's opened relative to `dirfd`
+ * @param path is a UTF-8 string naming a filesystem entity
  * @param flags must have one of the following under the `O_ACCMODE` bits:
- *     - `O_RDONLY`     to open `file` for reading only
- *     - `O_WRONLY`     to open `file` for writing
- *     - `O_RDWR`       to open `file` for reading and writing
+ *     - `O_RDONLY`     to open `path` for reading only
+ *     - `O_WRONLY`     to open `path` for writing
+ *     - `O_RDWR`       to open `path` for reading and writing
  *     The following may optionally be bitwise or'd into `flags`:
  *     - `O_CREAT`      create file if it doesn't exist
- *     - `O_TRUNC`      automatic `ftruncate(fd,0)` if exists
+ *     - `O_TRUNC`      automatic `ftruncate(fd,0)` if exists (atomic on unix)
  *     - `O_CLOEXEC`    automatic close() upon execve()
  *     - `O_EXCL`       exclusive access (see below)
  *     - `O_APPEND`     open file for appending only
  *     - `O_NOFOLLOW`   fail with ELOOP if it's a symlink
  *     - `O_NONBLOCK`   asks read/write to fail with `EAGAIN` rather than block
  *     - `O_EXEC`       open file for execution only; see fexecve()
- *     - `O_NOCTTY`     prevents `file` possibly becoming controlling terminal
+ *     - `O_NOCTTY`     prevents `path` from becoming the controlling terminal
+ *     - `O_DIRECTORY`  advisory feature for avoiding accidentally opening files
  *     - `O_DIRECT`     it's complicated (not supported on Apple and OpenBSD)
- *     - `O_DIRECTORY`  useful for stat'ing (hint on UNIX but required on NT)
  *     - `O_DSYNC`      it's complicated (zero on non-Linux/Apple)
  *     - `O_RSYNC`      it's complicated (zero on non-Linux/Apple)
  *     - `O_VERIFY`     it's complicated (zero on non-FreeBSD)
@@ -131,40 +127,48 @@
  *     the executable bit is set thrice too
  * @return file descriptor (which needs to be close()'d), or -1 w/ errno
  * @raise EPERM if pledge() is in play w/o appropriate rpath/wpath/cpath
- * @raise EACCES if unveil() is in play and didn't unveil your `file` path
- * @raise EACCES if we don't have permission to search a component of `file`
+ * @raise EACCES if unveil() is in play and didn't unveil your `path` path
+ * @raise EACCES if we don't have permission to search a component of `path`
  * @raise EACCES if file exists but requested `flags & O_ACCMODE` was denied
  * @raise EACCES if file doesn't exist and parent dir lacks write permissions
  * @raise EACCES if `O_TRUNC` was specified in `flags` but writing was denied
- * @raise ENOTSUP if `file` is on zip file system and `dirfd` isn't `AT_FDCWD`
- * @raise ENOTDIR if a directory component in `file` exists as non-directory
- * @raise ENOTDIR if `file` is relative and `dirfd` isn't an open directory
- * @raise EROFS when writing is requested w/ `file` on read-only filesystem
- * @raise ENAMETOOLONG if symlink-resolved `file` length exceeds `PATH_MAX`
- * @raise ENAMETOOLONG if component in `file` exists longer than `NAME_MAX`
- * @raise ENOTSUP if `file` is on zip file system and process is vfork()'d
- * @raise ENOSPC if file system is full when `file` would be `O_CREAT`ed
+ * @raise ENOTSUP if `path` is on zip file system and `dirfd` isn't `AT_FDCWD`
+ * @raise ENOEXEC if `path` is a zip path and this executable isn't a zip file
+ * @raise ENOTDIR if a directory component in `path` exists as non-directory
+ * @raise ENOTDIR if `path` ends with a trailing slash and refers to a file
+ * @raise ENOTDIR if `path` is relative and `dirfd` isn't an open directory
+ * @raise ENOTDIR if `path` isn't a directory and `O_DIRECTORY` was passed
+ * @raise EILSEQ if `path` contains illegal UTF-8 sequences (Windows/MacOS)
+ * @raise EROFS when writing is requested w/ `path` on read-only filesystem
+ * @raise ENAMETOOLONG if symlink-resolved `path` length exceeds `PATH_MAX`
+ * @raise ENAMETOOLONG if component in `path` exists longer than `NAME_MAX`
+ * @raise ENAMETOOLONG if `path` is relative and longer than 260 characters
+ * @raise ENOTSUP if `path` is on zip file system and process is vfork()'d
+ * @raise ENOSPC if file system is full when `path` would be `O_CREAT`ed
  * @raise EINTR if we needed to block and a signal was delivered instead
- * @raise EEXIST if `O_CREAT|O_EXCL` are used and `file` already existed
+ * @raise EEXIST if `O_CREAT|O_EXCL` are used and `path` already existed
+ * @raise EINVAL if ASCII control codes are used in `path` on Windows
+ * @raise EINVAL if `O_TRUNC` is specified in `O_RDONLY` mode
+ * @raise EINVAL if `flags` contains unsupported bits
  * @raise ECANCELED if thread was cancelled in masked mode
- * @raise ENOENT if `file` doesn't exist when `O_CREAT` isn't in `flags`
- * @raise ENOENT if `file` points to a string that's empty
+ * @raise ENOENT if `path` doesn't exist when `O_CREAT` isn't in `flags`
+ * @raise ENOENT if `path` points to a string that's empty
  * @raise ENOMEM if insufficient memory was available
  * @raise EMFILE if process `RLIMIT_NOFILE` has been reached
  * @raise ENFILE if system-wide file limit has been reached
- * @raise EOPNOTSUPP if `file` names a named socket
- * @raise EFAULT if `file` points to invalid memory
- * @raise ETXTBSY if writing is requested on `file` that's being executed
- * @raise ELOOP if `flags` had `O_NOFOLLOW` and `file` is a symbolic link
- * @raise ELOOP if a loop was detected resolving components of `file`
- * @raise EISDIR if writing is requested and `file` names a directory
+ * @raise EOPNOTSUPP if `path` names a named socket
+ * @raise EFAULT if `path` points to invalid memory
+ * @raise ETXTBSY if writing is requested on `path` that's being executed
+ * @raise ELOOP if `flags` had `O_NOFOLLOW` and `path` is a symbolic link
+ * @raise ELOOP if a loop was detected resolving components of `path`
+ * @raise EISDIR if writing is requested and `path` names a directory
  * @cancellationpoint
  * @asyncsignalsafe
  * @restartable
  * @threadsafe
  * @vforksafe
  */
-int openat(int dirfd, const char *file, int flags, ...) {
+int openat(int dirfd, const char *path, int flags, ...) {
   int rc;
   va_list va;
   unsigned mode;
@@ -174,32 +178,48 @@ int openat(int dirfd, const char *file, int flags, ...) {
   va_end(va);
   BEGIN_CANCELLATION_POINT;
 
-  if (file && (!IsAsan() || __asan_is_valid_str(file))) {
-    if (!__isfdkind(dirfd, kFdZip)) {
-      if (_weaken(__zipos_open) &&
-          _weaken(__zipos_parseuri)(file, &zipname) != -1) {
-        if (!__vforked && dirfd == AT_FDCWD) {
-          rc = _weaken(__zipos_open)(&zipname, flags);
-        } else {
-          rc = enotsup(); /* TODO */
-        }
-      } else if (!IsWindows() && !IsMetal()) {
-        rc = sys_openat(dirfd, file, flags, mode);
-      } else if (IsMetal()) {
-        rc = sys_openat_metal(dirfd, file, flags, mode);
-      } else {
-        rc = sys_open_nt(dirfd, file, flags, mode);
-      }
-    } else {
-      rc = enotsup(); /* TODO */
-    }
-  } else {
+  if (!path || (IsAsan() && !__asan_is_valid_str(path))) {
     rc = efault();
+  } else if (__isfdkind(dirfd, kFdZip)) {
+    rc = enotsup();  // TODO
+  } else if (_weaken(__zipos_open) &&
+             _weaken(__zipos_parseuri)(path, &zipname) != -1) {
+    if (!__vforked && dirfd == AT_FDCWD) {
+      rc = _weaken(__zipos_open)(&zipname, flags);
+    } else {
+      rc = enotsup();  // TODO
+    }
+  } else if ((flags & O_ACCMODE) == O_RDONLY && (flags & O_TRUNC)) {
+    rc = einval();  // Every OS except OpenBSD actually does this D:
+  } else if (IsLinux() || IsXnu() || IsFreebsd() || IsOpenbsd() || IsNetbsd()) {
+    rc = sys_openat(dirfd, path, flags, mode);
+    if (IsFreebsd()) {
+      // Address FreeBSD divergence from IEEE Std 1003.1-2008 (POSIX.1)
+      // in the case when O_NOFOLLOW is used, but fails due to symlink.
+      if (rc == -1 && errno == EMLINK) {
+        errno = ELOOP;
+      }
+    }
+    if (IsNetbsd()) {
+      // Address NetBSD divergence from IEEE Std 1003.1-2008 (POSIX.1)
+      // in the case when O_NOFOLLOW is used but fails due to symlink.
+      if (rc == -1 && errno == EFTYPE) {
+        errno = ELOOP;
+      }
+    }
+  } else if (IsMetal()) {
+    rc = sys_openat_metal(dirfd, path, flags, mode);
+  } else if (IsWindows()) {
+    rc = sys_open_nt(dirfd, path, flags, mode);
+  } else {
+    rc = enosys();
   }
 
   END_CANCELLATION_POINT;
-  STRACE("openat(%s, %#s, %s, %#o) → %d% m", DescribeDirfd(dirfd), file,
+  STRACE("openat(%s, %#s, %s, %#o) → %d% m", DescribeDirfd(dirfd), path,
          DescribeOpenFlags(flags), (flags & (O_CREAT | O_TMPFILE)) ? mode : 0,
          rc);
   return rc;
 }
+
+__strong_reference(openat, openat64);
diff --git a/libc/calls/pipe-nt.c b/libc/calls/pipe-nt.c
index 7698dbbc1..1321343ef 100644
--- a/libc/calls/pipe-nt.c
+++ b/libc/calls/pipe-nt.c
@@ -58,11 +58,11 @@ textwindows int sys_pipe_nt(int pipefd[2], unsigned flags) {
     if ((hout = CreateFile(pipename, kNtGenericWrite, 0, &kNtIsInheritable,
                            kNtOpenExisting, kNtFileFlagOverlapped, 0)) != -1) {
       g_fds.p[reader].kind = kFdFile;
-      g_fds.p[reader].flags = flags;
+      g_fds.p[reader].flags = O_RDONLY | flags;
       g_fds.p[reader].mode = 0010444;
       g_fds.p[reader].handle = hin;
       g_fds.p[writer].kind = kFdFile;
-      g_fds.p[writer].flags = flags;
+      g_fds.p[writer].flags = O_WRONLY | flags;
       g_fds.p[writer].mode = 0010222;
       g_fds.p[writer].handle = hout;
       pipefd[0] = reader;
diff --git a/libc/calls/pipe2.c b/libc/calls/pipe2.c
index 2cfcc625c..5a75571f0 100644
--- a/libc/calls/pipe2.c
+++ b/libc/calls/pipe2.c
@@ -30,7 +30,8 @@
  * This function offers atomic operation on all supported platforms
  * except for XNU and RHEL5 where it's polyfilled.
  *
- * @params flags may contain `O_CLOEXEC`, `O_NONBLOCK`, and `O_DIRECT`
+ * @params flags may contain `O_CLOEXEC`, `O_NONBLOCK`, or the non-POSIX
+ *     packet mode flag `O_DIRECT`, which is `EINVAL` on MacOS / OpenBSD
  * @raise EINVAL if flags has invalid or unsupported bits
  * @raise EFAULT if `pipefd` doesn't point to valid memory
  * @raise EMFILE if process `RLIMIT_NOFILE` has been reached
@@ -41,7 +42,7 @@
  */
 int pipe2(int pipefd[hasatleast 2], int flags) {
   int rc;
-  if (flags & ~(O_CLOEXEC | O_NONBLOCK | O_DIRECT)) {
+  if (flags & ~(O_CLOEXEC | O_NONBLOCK | (O_DIRECT != -1u ? O_DIRECT : 0))) {
     return einval();
   } else if (!pipefd ||
              (IsAsan() && !__asan_is_valid(pipefd, sizeof(int) * 2))) {
diff --git a/libc/calls/posix_fadvise.c b/libc/calls/posix_fadvise.c
index 8582b720e..1582e4280 100644
--- a/libc/calls/posix_fadvise.c
+++ b/libc/calls/posix_fadvise.c
@@ -18,6 +18,8 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/assert.h"
 #include "libc/calls/calls.h"
+#include "libc/calls/internal.h"
+#include "libc/calls/struct/fd.internal.h"
 #include "libc/calls/syscall-nt.internal.h"
 #include "libc/calls/syscall-sysv.internal.h"
 #include "libc/dce.h"
@@ -41,13 +43,16 @@ int sys_fadvise_netbsd(int, int, int64_t, int64_t, int) asm("sys_fadvise");
  * @raise EBADF if `fd` isn't a valid file descriptor
  * @raise EINVAL if `advice` is invalid or `len` is huge
  * @raise ESPIPE if `fd` refers to a pipe
+ * @raise ENOTSUP if `fd` is a /zip file
  * @raise ENOSYS on XNU and OpenBSD
  * @returnserrno
  * @threadsafe
  */
 errno_t posix_fadvise(int fd, int64_t offset, int64_t len, int advice) {
   int rc, e = errno;
-  if (IsLinux()) {
+  if (fd < g_fds.n && g_fds.p[fd].kind == kFdZip) {
+    rc = enotsup();
+  } else if (IsLinux()) {
     rc = sys_fadvise(fd, offset, len, advice);
   } else if (IsFreebsd()) {
     rc = sys_fadvise(fd, offset, len, advice);
diff --git a/libc/calls/pread.c b/libc/calls/pread.c
index 6776e1f6c..7a124eb94 100644
--- a/libc/calls/pread.c
+++ b/libc/calls/pread.c
@@ -29,8 +29,8 @@
 #include "libc/intrin/weaken.h"
 #include "libc/macros.internal.h"
 #include "libc/runtime/runtime.h"
-#include "libc/sysv/errfuns.h"
 #include "libc/runtime/zipos.internal.h"
+#include "libc/sysv/errfuns.h"
 
 /**
  * Reads from file at offset.
@@ -71,6 +71,8 @@ ssize_t pread(int fd, void *buf, size_t size, int64_t offset) {
         (struct iovec[]){{buf, size}}, 1, offset);
   } else if (!IsWindows()) {
     rc = sys_pread(fd, buf, size, offset, offset);
+  } else if (__isfdkind(fd, kFdSocket)) {
+    rc = espipe();
   } else if (__isfdkind(fd, kFdFile)) {
     rc = sys_read_nt(&g_fds.p[fd], (struct iovec[]){{buf, size}}, 1, offset);
   } else {
diff --git a/libc/calls/preadv.c b/libc/calls/preadv.c
index b98c598c9..ab64f22dc 100644
--- a/libc/calls/preadv.c
+++ b/libc/calls/preadv.c
@@ -59,7 +59,11 @@ static ssize_t Preadv(int fd, struct iovec *iov, int iovlen, int64_t off) {
 
   if (IsWindows()) {
     if (fd < g_fds.n) {
-      return sys_read_nt(g_fds.p + fd, iov, iovlen, off);
+      if (g_fds.p[fd].kind == kFdSocket) {
+        return espipe();
+      } else {
+        return sys_read_nt(g_fds.p + fd, iov, iovlen, off);
+      }
     } else {
       return ebadf();
     }
diff --git a/libc/calls/pwrite.c b/libc/calls/pwrite.c
index 475ad364f..db94c6dfe 100644
--- a/libc/calls/pwrite.c
+++ b/libc/calls/pwrite.c
@@ -64,6 +64,8 @@ ssize_t pwrite(int fd, const void *buf, size_t size, int64_t offset) {
     rc = ebadf();
   } else if (!IsWindows()) {
     rc = sys_pwrite(fd, buf, size, offset, offset);
+  } else if (__isfdkind(fd, kFdSocket)) {
+    rc = espipe();
   } else if (__isfdkind(fd, kFdFile)) {
     rc = sys_write_nt(fd, (struct iovec[]){{buf, size}}, 1, offset);
   } else {
diff --git a/libc/calls/pwritev.c b/libc/calls/pwritev.c
index c2cade35d..3e9e840f0 100644
--- a/libc/calls/pwritev.c
+++ b/libc/calls/pwritev.c
@@ -54,7 +54,11 @@ static ssize_t Pwritev(int fd, const struct iovec *iov, int iovlen,
 
   if (IsWindows()) {
     if (fd < g_fds.n) {
-      return sys_write_nt(fd, iov, iovlen, off);
+      if (g_fds.p[fd].kind == kFdSocket) {
+        return espipe();
+      } else {
+        return sys_write_nt(fd, iov, iovlen, off);
+      }
     } else {
       return ebadf();
     }
diff --git a/libc/calls/renameat-nt.c b/libc/calls/renameat-nt.c
index 8b094783d..3399bcc72 100644
--- a/libc/calls/renameat-nt.c
+++ b/libc/calls/renameat-nt.c
@@ -17,17 +17,74 @@
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/calls/syscall_support-nt.internal.h"
+#include "libc/errno.h"
+#include "libc/nt/enum/fileflagandattributes.h"
 #include "libc/nt/enum/movefileexflags.h"
+#include "libc/nt/errors.h"
 #include "libc/nt/files.h"
+#include "libc/nt/runtime.h"
+#include "libc/nt/thunk/msabi.h"
+#include "libc/str/str.h"
+#include "libc/sysv/errfuns.h"
+
+__msabi extern typeof(GetFileAttributes) *const __imp_GetFileAttributesW;
+__msabi extern typeof(RemoveDirectory) *const __imp_RemoveDirectoryW;
+
+static textwindows bool StripTrailingSlash(char16_t *path) {
+  size_t n = strlen16(path);
+  bool had_trailing_slash = false;
+  if (n > 1 && path[n - 1] == '\\') {
+    had_trailing_slash = true;
+    path[--n] = 0;
+  }
+  return had_trailing_slash;
+}
 
 textwindows int sys_renameat_nt(int olddirfd, const char *oldpath, int newdirfd,
                                 const char *newpath) {
+
+  // translate unix to windows paths
   char16_t oldpath16[PATH_MAX];
   char16_t newpath16[PATH_MAX];
   if (__mkntpathat(olddirfd, oldpath, 0, oldpath16) == -1 ||
       __mkntpathat(newdirfd, newpath, 0, newpath16) == -1) {
     return -1;
   }
+
+  // strip trailing slash
+  // win32 will einval otherwise
+  // normally this is handled by __fix_enotdir()
+  bool old_must_be_dir = StripTrailingSlash(oldpath16);
+  bool new_must_be_dir = StripTrailingSlash(newpath16);
+
+  // test for some known error conditions ahead of time
+  // the enotdir check can't be done reactively
+  // ideally we should resolve symlinks first
+  uint32_t oldattr = __imp_GetFileAttributesW(oldpath16);
+  uint32_t newattr = __imp_GetFileAttributesW(newpath16);
+  if ((old_must_be_dir && oldattr != -1u &&
+       !(oldattr & kNtFileAttributeDirectory)) ||
+      (new_must_be_dir && newattr != -1u &&
+       !(newattr & kNtFileAttributeDirectory))) {
+    return enotdir();
+  }
+  if (oldattr != -1u && newattr != -1u) {
+    if (!(oldattr & kNtFileAttributeDirectory) &&
+        (newattr & kNtFileAttributeDirectory)) {
+      return eisdir();  // new is directory, but old isn't a directory
+    } else if ((oldattr & kNtFileAttributeDirectory) &&
+               !(newattr & kNtFileAttributeDirectory)) {
+      return enotdir();  // old is directory, but new isn't a directory
+    } else if ((oldattr & kNtFileAttributeDirectory) &&
+               (newattr & kNtFileAttributeDirectory)) {
+      // both old and new are directories
+      if (!__imp_RemoveDirectoryW(newpath16) &&
+          GetLastError() == kNtErrorDirNotEmpty) {
+        return enotempty();
+      }
+    }
+  }
+
   if (MoveFileEx(oldpath16, newpath16, kNtMovefileReplaceExisting)) {
     return 0;
   } else {
diff --git a/libc/calls/struct/timeval.h b/libc/calls/struct/timeval.h
index 23642e7ca..2d59bf883 100644
--- a/libc/calls/struct/timeval.h
+++ b/libc/calls/struct/timeval.h
@@ -30,6 +30,7 @@ struct timeval timeval_add(struct timeval, struct timeval) pureconst;
 struct timeval timeval_sub(struct timeval, struct timeval) pureconst;
 struct timeval timeval_subz(struct timeval, struct timeval) pureconst;
 int64_t timeval_toseconds(struct timeval);
+int64_t timeval_tomicros(struct timeval);
 struct timeval timespec_totimeval(struct timespec) pureconst;
 static inline struct timeval timeval_fromseconds(int64_t __x) {
   return (struct timeval){__x};
diff --git a/libc/calls/ualarm.c b/libc/calls/ualarm.c
new file mode 100644
index 000000000..47ecc8233
--- /dev/null
+++ b/libc/calls/ualarm.c
@@ -0,0 +1,40 @@
+/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
+│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8                                :vi│
+╞══════════════════════════════════════════════════════════════════════════════╡
+│ Copyright 2020 Justine Alexandra Roberts Tunney                              │
+│                                                                              │
+│ Permission to use, copy, modify, and/or distribute this software for         │
+│ any purpose with or without fee is hereby granted, provided that the         │
+│ above copyright notice and this permission notice appear in all copies.      │
+│                                                                              │
+│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                │
+│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                │
+│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             │
+│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         │
+│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        │
+│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               │
+│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
+│ PERFORMANCE OF THIS SOFTWARE.                                                │
+╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/assert.h"
+#include "libc/calls/calls.h"
+#include "libc/calls/struct/itimerval.h"
+#include "libc/calls/struct/timeval.h"
+#include "libc/sysv/consts/itimer.h"
+
+/**
+ * Sets microsecond-precision alarm.
+ *
+ * This generates a `SIGALRM` signal after `usecs` microseconds. If
+ * `reload` is non-zero, then it'll keep generating `SIGALRM` every
+ * `reload` microseconds after the first signal.
+ *
+ * @asyncsignalsafe
+ */
+unsigned ualarm(unsigned usecs, unsigned reload) {
+  struct itimerval it, old;
+  it.it_value = timeval_frommicros(usecs);
+  it.it_interval = timeval_frommicros(reload);
+  npassert(!setitimer(ITIMER_REAL, &it, &old));
+  return timeval_tomicros(old.it_value);
+}
diff --git a/libc/calls/unlinkat-nt.c b/libc/calls/unlinkat-nt.c
index d65bb2fe0..6cced09da 100644
--- a/libc/calls/unlinkat-nt.c
+++ b/libc/calls/unlinkat-nt.c
@@ -33,48 +33,7 @@
 #include "libc/nt/synchronization.h"
 #include "libc/str/str.h"
 #include "libc/sysv/consts/at.h"
-
-/**
- * Performs synchronization on directory of pathname.
- *
- * This code is intended to help prevent subsequent i/o operations
- * from failing for no reason at all. For example a unit test that
- * repeatedly opens and unlinks the same filename.
- */
-static textwindows int SyncDirectory(int df, char16_t path[PATH_MAX], int n) {
-  int rc;
-  int64_t fh;
-  char16_t *p;
-  if ((p = memrchr16(path, '\\', n))) {
-    if (p - path == 2 && path[1] == ':') return 0;  // XXX: avoid syncing volume
-    *p = 0;
-  } else {
-    if (df != AT_FDCWD) {
-      if (FlushFileBuffers(df)) {
-        return 0;
-      } else {
-        return -1;
-      }
-    }
-    path[0] = '.';
-    path[1] = 0;
-  }
-  if ((fh = CreateFile(
-           path, kNtFileGenericWrite,
-           kNtFileShareRead | kNtFileShareWrite | kNtFileShareDelete, 0,
-           kNtOpenExisting, kNtFileAttributeNormal | kNtFileFlagBackupSemantics,
-           0)) != -1) {
-    if (FlushFileBuffers(fh)) {
-      rc = 0;
-    } else {
-      rc = -1;
-    }
-    CloseHandle(fh);
-  } else {
-    rc = -1;
-  }
-  return rc;
-}
+#include "libc/sysv/errfuns.h"
 
 static textwindows bool IsDirectorySymlink(const char16_t *path) {
   int e;
@@ -102,13 +61,11 @@ static textwindows int sys_rmdir_nt(const char16_t *path) {
     if (RemoveDirectory(path)) {
       return 0;
     }
-    /*
-     * Files can linger, for absolutely no reason.
-     * Possibly some Windows Defender bug on Win7.
-     * Sleep for up to one second w/ expo backoff.
-     * Alternative is use Microsoft internal APIs.
-     * Never could have imagined it'd be this bad.
-     */
+    // Files can linger, for absolutely no reason.
+    // Possibly some Windows Defender bug on Win7.
+    // Sleep for up to one second w/ expo backoff.
+    // Alternative is use Microsoft internal APIs.
+    // Never could have imagined it'd be this bad.
     if (GetLastError() == kNtErrorDirNotEmpty && ms <= 2048) {
       errno = e;
       Sleep(ms);
@@ -130,19 +87,45 @@ static textwindows int sys_unlink_nt(const char16_t *path) {
   }
 }
 
-textwindows int sys_unlinkat_nt(int dirfd, const char *path, int flags) {
-  int n, rc;
-  char16_t path16[PATH_MAX];
-  if ((n = __mkntpathat(dirfd, path, 0, path16)) == -1) {
-    rc = -1;
-  } else if (flags & AT_REMOVEDIR) {
-    rc = sys_rmdir_nt(path16);
+textwindows int sys_unlinkat_nt_impl(const char16_t *path, int flags) {
+  if (flags & AT_REMOVEDIR) {
+    return sys_rmdir_nt(path);
   } else {
-    rc = sys_unlink_nt(path16);
-    if (rc != -1) {
-      // TODO(jart): prove that it helps first
-      // rc = SyncDirectory(dirfd, path16, n);
+    return sys_unlink_nt(path);
+  }
+}
+
+textwindows int sys_unlinkat_nt(int dirfd, const char *path, int flags) {
+  char16_t path16[PATH_MAX];
+
+  // check validity of flags
+  if (flags & ~AT_REMOVEDIR) {
+    return einval();
+  }
+
+  // translate unix to windows path
+  int n;
+  if ((n = __mkntpathat(dirfd, path, 0, path16)) == -1) {
+    return -1;
+  }
+
+  // optimistic first attempt
+  int e = errno;
+  int rc = sys_unlinkat_nt_impl(path16, flags);
+
+  // reactively ensure unlink() deletes read-only files
+  if (rc == -1 && errno == kNtErrorAccessDenied) {
+    uint32_t attr;
+    if ((attr = GetFileAttributes(path16)) != -1u &&
+        (attr & kNtFileAttributeReadonly) &&
+        SetFileAttributes(path16, attr & ~kNtFileAttributeReadonly)) {
+      errno = e;
+      rc = sys_unlinkat_nt_impl(path16, flags);
+    } else {
+      errno = kNtErrorAccessDenied;
     }
   }
+
+  // return status
   return __fix_enotdir(rc, path16);
 }
diff --git a/libc/calls/weirdtypes.h b/libc/calls/weirdtypes.h
index 3dc1e8b6f..edcbb701e 100644
--- a/libc/calls/weirdtypes.h
+++ b/libc/calls/weirdtypes.h
@@ -28,7 +28,7 @@ typedef int64_t register_t;
 typedef uint16_t sa_family_t; /* bsd:uint8_t */
 typedef uint32_t socklen_t;
 typedef uint32_t speed_t;
-typedef int64_t suseconds_t;   /* int32_t on xnu */
+typedef uint32_t suseconds_t;
 typedef uint64_t useconds_t;   /* uint32_t on xnu */
 typedef int64_t syscall_arg_t; /* uint64_t on xnu */
 typedef uint32_t tcflag_t;
diff --git a/libc/calls/write-nt.c b/libc/calls/write-nt.c
index 41d97dc53..59f9d4885 100644
--- a/libc/calls/write-nt.c
+++ b/libc/calls/write-nt.c
@@ -26,11 +26,13 @@
 #include "libc/intrin/strace.internal.h"
 #include "libc/intrin/weaken.h"
 #include "libc/macros.internal.h"
+#include "libc/nt/enum/filetype.h"
 #include "libc/nt/errors.h"
 #include "libc/nt/files.h"
 #include "libc/nt/runtime.h"
 #include "libc/nt/struct/overlapped.h"
 #include "libc/runtime/runtime.h"
+#include "libc/sysv/consts/o.h"
 #include "libc/sysv/consts/sicode.h"
 #include "libc/sysv/consts/sig.h"
 #include "libc/sysv/errfuns.h"
@@ -42,11 +44,21 @@ static textwindows ssize_t sys_write_nt_impl(int fd, void *data, size_t size,
   bool32 ok;
   uint32_t sent;
   int64_t handle;
+
   if (g_fds.p[fd].kind == kFdConsole) {
     handle = g_fds.p[fd].extra;  // get write end of console
   } else {
     handle = g_fds.p[fd].handle;
   }
+
+  // don't use pread() or pwrite() on a pipe
+  if (offset != -1) {
+    uint32_t filetype = GetFileType(handle);
+    if (filetype == kNtFileTypeChar || filetype == kNtFileTypePipe) {
+      return espipe();
+    }
+  }
+
   size = MIN(size, 0x7ffff000);
   if (offset == -1) {
     // perform simple blocking write
diff --git a/libc/intrin/createfile.c b/libc/intrin/createfile.c
index 33e0d420f..d2fa41201 100644
--- a/libc/intrin/createfile.c
+++ b/libc/intrin/createfile.c
@@ -66,6 +66,7 @@ TryAgain:
         if ((dwDesiredAccess & kNtGenericExecute) &&
             (dwCreationDisposition == kNtOpenExisting ||
              dwCreationDisposition == kNtTruncateExisting)) {
+          NTTRACE("CreateFile removed kNtGenericExecute");
           dwDesiredAccess &= ~kNtGenericExecute;
           goto TryAgain;
         }
diff --git a/libc/intrin/describentfileaccessflags.c b/libc/intrin/describentfileaccessflags.c
index a29c17066..b25cd9a4b 100644
--- a/libc/intrin/describentfileaccessflags.c
+++ b/libc/intrin/describentfileaccessflags.c
@@ -20,50 +20,59 @@
 #include "libc/macros.internal.h"
 #include "libc/nt/enum/accessmask.h"
 #include "libc/nt/enum/filesharemode.h"
+// clang-format off
 
 static const struct DescribeFlags kFileAccessflags[] = {
-    {kNtFileAllAccess, "FileAllAccess"},                    // order matters
-    {kNtFileGenericRead, "FileGenericRead"},                // order matters
-    {kNtFileGenericWrite, "FileGenericWrite"},              // order matters
-    {kNtFileGenericExecute, "FileGenericExecute"},          // order matters
-    {kNtGenericRead, "GenericRead"},                        //
-    {kNtGenericWrite, "GenericWrite"},                      //
-    {kNtGenericExecute, "GenericExecute"},                  //
-    {kNtGenericAll, "GenericAll"},                          //
-    {kNtDelete, "Delete"},                                  //
-    {kNtReadControl, "ReadControl"},                        //
-    {kNtWriteDac, "WriteDac"},                              //
-    {kNtWriteOwner, "WriteOwner"},                          //
-    {kNtSynchronize, "Synchronize"},                        //
-    {kNtStandardRightsRequired, "StandardRightsRequired"},  //
-    {kNtAccessSystemSecurity, "AccessSystemSecurity"},      //
-    {kNtMaximumAllowed, "MaximumAllowed"},                  //
-    {kNtFileReadData, "FileReadData"},                      //
-    {kNtFileListDirectory, "FileListDirectory"},            //
-    {kNtFileWriteData, "FileWriteData"},                    //
-    {kNtFileAddFile, "FileAddFile"},                        //
-    {kNtFileAppendData, "FileAppendData"},                  //
-    {kNtFileAddSubdirectory, "FileAddSubdirectory"},        //
-    {kNtFileCreatePipeInstance, "FileCreatePipeInstance"},  //
-    {kNtFileReadEa, "FileReadEa"},                          //
-    {kNtFileWriteEa, "FileWriteEa"},                        //
-    {kNtFileExecute, "FileExecute"},                        //
-    {kNtFileTraverse, "FileTraverse"},                      //
-    {kNtFileDeleteChild, "FileDeleteChild"},                //
-    {kNtFileReadAttributes, "FileReadAttributes"},          //
-    {kNtFileWriteAttributes, "FileWriteAttributes"},        //
-    {kNtTokenAssignPrimary, "TokenAssignPrimary"},          //
-    {kNtTokenDuplicate, "TokenDuplicate"},                  //
-    {kNtTokenImpersonate, "TokenImpersonate"},              //
-    {kNtTokenQuery, "TokenQuery"},                          //
-    {kNtTokenQuerySource, "TokenQuerySource"},              //
-    {kNtTokenAdjustPrivileges, "TokenAdjustPrivileges"},    //
-    {kNtTokenAdjustGroups, "TokenAdjustGroups"},            //
-    {kNtTokenAdjustDefault, "TokenAdjustDefault"},          //
-    {kNtTokenAdjustSessionid, "TokenAdjustSessionid"},      //
+    {kNtFileAllAccess, "kNtFileAllAccess"},
+    {kNtFileGenericRead|kNtFileGenericWrite|kNtFileGenericExecute,
+     "kNtFileGenericRead|kNtFileGenericWrite|kNtFileGenericExecute"},
+    {kNtFileGenericRead|kNtFileGenericWrite,
+     "kNtFileGenericRead|kNtFileGenericWrite"},
+    {kNtFileGenericRead|kNtFileGenericExecute,
+     "kNtFileGenericRead|kNtFileGenericExecute"},
+    {kNtFileGenericWrite|kNtFileGenericExecute,
+     "kNtFileGenericWrite|kNtFileGenericExecute"},
+    {kNtFileGenericRead, "kNtFileGenericRead"},
+    {kNtFileGenericWrite, "kNtFileGenericWrite"},
+    {kNtFileGenericExecute, "kNtFileGenericExecute"},
+    {kNtGenericRead, "kNtGenericRead"},
+    {kNtGenericWrite, "kNtGenericWrite"},
+    {kNtGenericExecute, "kNtGenericExecute"},
+    {kNtGenericAll, "kNtGenericAll"},
+    {kNtDelete, "kNtDelete"},
+    {kNtReadControl, "kNtReadControl"},
+    {kNtWriteDac, "kNtWriteDac"},
+    {kNtWriteOwner, "kNtWriteOwner"},
+    {kNtSynchronize, "kNtSynchronize"},
+    {kNtStandardRightsRequired, "kNtStandardRightsRequired"},
+    {kNtAccessSystemSecurity, "kNtAccessSystemSecurity"},
+    {kNtMaximumAllowed, "kNtMaximumAllowed"},
+    {kNtFileReadData, "kNtFileReadData"},
+    {kNtFileListDirectory, "kNtFileListDirectory"},
+    {kNtFileWriteData, "kNtFileWriteData"},
+    {kNtFileAddFile, "kNtFileAddFile"},
+    {kNtFileAppendData, "kNtFileAppendData"},
+    {kNtFileAddSubdirectory, "kNtFileAddSubdirectory"},
+    {kNtFileCreatePipeInstance, "kNtFileCreatePipeInstance"},
+    {kNtFileReadEa, "kNtFileReadEa"},
+    {kNtFileWriteEa, "kNtFileWriteEa"},
+    {kNtFileExecute, "kNtFileExecute"},
+    {kNtFileTraverse, "kNtFileTraverse"},
+    {kNtFileDeleteChild, "kNtFileDeleteChild"},
+    {kNtFileReadAttributes, "kNtFileReadAttributes"},
+    {kNtFileWriteAttributes, "kNtFileWriteAttributes"},
+    {kNtTokenAssignPrimary, "kNtTokenAssignPrimary"},
+    {kNtTokenDuplicate, "kNtTokenDuplicate"},
+    {kNtTokenImpersonate, "kNtTokenImpersonate"},
+    {kNtTokenQuery, "kNtTokenQuery"},
+    {kNtTokenQuerySource, "kNtTokenQuerySource"},
+    {kNtTokenAdjustPrivileges, "kNtTokenAdjustPrivileges"},
+    {kNtTokenAdjustGroups, "kNtTokenAdjustGroups"},
+    {kNtTokenAdjustDefault, "kNtTokenAdjustDefault"},
+    {kNtTokenAdjustSessionid, "kNtTokenAdjustSessionid"},
 };
 
 const char *(DescribeNtFileAccessFlags)(char buf[512], uint32_t x) {
   return DescribeFlags(buf, 512, kFileAccessflags, ARRAYLEN(kFileAccessflags),
-                       "kNt", x);
+                       "", x);
 }
diff --git a/libc/intrin/strsignal_r.c b/libc/intrin/strsignal_r.c
index bcea1a96d..09b57ed70 100644
--- a/libc/intrin/strsignal_r.c
+++ b/libc/intrin/strsignal_r.c
@@ -36,12 +36,16 @@
  * @asyncsignalsafe
  * @threadsafe
  */
-privileged char *strsignal_r(int sig, char buf[hasatleast 15]) {
+privileged dontdiscard char *strsignal_r(int sig, char buf[15]) {
   int i;
   char *p;
   const char *s;
-  if (!sig) return "0";
-  if ((s = GetMagnumStr(kSignalNames, sig))) return s;
+  if (!sig) {
+    return "0";
+  }
+  if ((s = GetMagnumStr(kSignalNames, sig))) {
+    return s;
+  }
   if (SIGRTMIN <= sig && sig <= SIGRTMAX) {
     sig -= SIGRTMIN;
     buf[0] = 'S';
diff --git a/libc/nt/createfile.h b/libc/nt/createfile.h
index 9030fb3c4..ae1a11072 100644
--- a/libc/nt/createfile.h
+++ b/libc/nt/createfile.h
@@ -18,8 +18,7 @@ int64_t CreateFileA(
     uint32_t dwFlagsAndAttributes, /* libc/nt/enum/fileflagandattributes.h */
     int64_t opt_hTemplateFile) paramsnonnull((1));
 
-int GetNtOpenFlags(int flags, int mode, uint32_t *out_perm, uint32_t *out_share,
-                   uint32_t *out_disp, uint32_t *out_attr);
+int GetNtOpenFlags(int, int, uint32_t *, uint32_t *, uint32_t *, uint32_t *);
 
 COSMOPOLITAN_C_END_
 #endif /* !(__ASSEMBLER__ + __LINKER__ + 0) */
diff --git a/libc/runtime/clone.c b/libc/runtime/clone.c
index 2df2e2a30..59065f263 100644
--- a/libc/runtime/clone.c
+++ b/libc/runtime/clone.c
@@ -20,6 +20,7 @@
 #include "libc/assert.h"
 #include "libc/atomic.h"
 #include "libc/calls/calls.h"
+#include "libc/calls/struct/sigset.h"
 #include "libc/calls/struct/ucontext-netbsd.internal.h"
 #include "libc/calls/syscall-sysv.internal.h"
 #include "libc/calls/wincrash.internal.h"
@@ -195,6 +196,9 @@ XnuThreadMain(void *pthread,                    // rdi
 
   func(arg, tid);
 
+  // avoid signal handler being triggered after we trash our stack
+  _sigblockall();
+
   // we no longer use the stack after this point
   // %rax = int bsdthread_terminate(%rdi = void *stackaddr,
   //                                %rsi = size_t freesize,
@@ -234,6 +238,8 @@ static wontreturn void FreebsdThreadMain(void *p) {
   struct CloneArgs *wt = p;
   *wt->ctid = wt->tid;
   wt->func(wt->arg, wt->tid);
+  // avoid signal handler being triggered after we trash our stack
+  _sigblockall();
   // we no longer use the stack after this point
   // void thr_exit(%rdi = long *state);
   asm volatile("movl\t$0,%0\n\t"       // *wt->ztid = 0
@@ -349,6 +355,8 @@ static wontreturn void NetbsdThreadMain(void *arg,                 // rdi
   ax = sys_gettid();
   *ctid = ax;
   func(arg, ax);
+  // avoid signal handler being triggered after we trash our stack
+  _sigblockall();
   // we no longer use the stack after this point
   // %eax = int __lwp_exit(void);
   asm volatile("movl\t$0,%2\n\t"  // *wt->ztid = 0
diff --git a/libc/runtime/zipos-normpath.c b/libc/runtime/zipos-normpath.c
index 9a6bdedce..b218cf2fd 100644
--- a/libc/runtime/zipos-normpath.c
+++ b/libc/runtime/zipos-normpath.c
@@ -34,7 +34,6 @@ size_t __zipos_normpath(char *d, const char *s, size_t n) {
                s[0] == '.' &&               //
                (!s[1] || s[1] == '/')) {
       // matched "/./" or "^.$" or "^./" or "/.$"
-      s += !!s[1];
     } else if ((p == d || p[-1] == '/') &&  //
                s[0] == '.' &&               //
                s[1] == '.' &&               //
diff --git a/libc/sock/sendmsg.c b/libc/sock/sendmsg.c
index fa38bcb12..33cd8440d 100644
--- a/libc/sock/sendmsg.c
+++ b/libc/sock/sendmsg.c
@@ -76,7 +76,7 @@ ssize_t sendmsg(int fd, const struct msghdr *msg, int flags) {
     } else if (__isfdkind(fd, kFdSocket)) {
       rc = sys_sendto_nt(fd, msg->msg_iov, msg->msg_iovlen, flags,
                          msg->msg_name, msg->msg_namelen);
-    } else if (__isfdkind(fd, kFdFile)) {
+    } else if (__isfdkind(fd, kFdFile)) {  // e.g. socketpair
       rc = sys_write_nt(fd, msg->msg_iov, msg->msg_iovlen, -1);
     } else {
       rc = enotsock();
diff --git a/libc/sock/socketpair-nt.c b/libc/sock/socketpair-nt.c
index 1800fc2d3..171724b16 100644
--- a/libc/sock/socketpair-nt.c
+++ b/libc/sock/socketpair-nt.c
@@ -80,12 +80,12 @@ textwindows int sys_socketpair_nt(int family, int type, int proto, int sv[2]) {
   if (h1 != -1) {
 
     g_fds.p[reader].kind = kFdFile;
-    g_fds.p[reader].flags = oflags;
+    g_fds.p[reader].flags = O_RDWR | oflags;
     g_fds.p[reader].mode = 0140444;
     g_fds.p[reader].handle = hpipe;
 
     g_fds.p[writer].kind = kFdFile;
-    g_fds.p[writer].flags = oflags;
+    g_fds.p[writer].flags = O_RDWR | oflags;
     g_fds.p[writer].mode = 0140222;
     g_fds.p[writer].handle = h1;
 
diff --git a/libc/str/istext.c b/libc/str/istext.c
index 460626572..66571f4dd 100644
--- a/libc/str/istext.c
+++ b/libc/str/istext.c
@@ -21,7 +21,7 @@
 /**
  * Returns true if buffer is most likely plaintext.
  */
-bool _istext(const void *data, size_t size) {
+bool istext(const void *data, size_t size) {
   const unsigned char *p, *pe;
   for (p = data, pe = p + size; p < pe; ++p) {
     if (*p <= 3) {
diff --git a/libc/str/isutf8.c b/libc/str/isutf8.c
index 446a07093..4231f1de1 100644
--- a/libc/str/isutf8.c
+++ b/libc/str/isutf8.c
@@ -21,8 +21,6 @@
 #include "libc/intrin/likely.h"
 #include "libc/str/str.h"
 
-typedef char xmm_t __attribute__((__vector_size__(16), __aligned__(16)));
-
 static const char kUtf8Dispatch[] = {
     0, 0, 1, 1, 1, 1, 1, 1,  // 0300 utf8-2
     1, 1, 1, 1, 1, 1, 1, 1,  // 0310
@@ -37,10 +35,10 @@ static const char kUtf8Dispatch[] = {
 /**
  * Returns true if text is utf-8.
  *
- *     _isutf8 n=0                  1 nanoseconds
- *     _isutf8 n=5                661 ps/byte          1,476 mb/s
- *     _isutf8 ascii n=22851       26 ps/byte             35 GB/s
- *     _isutf8 unicode n=3193     543 ps/byte          1,795 mb/s
+ *     isutf8 n=0                  1 nanoseconds
+ *     isutf8 n=5                661 ps/byte          1,476 mb/s
+ *     isutf8 ascii n=22851       26 ps/byte             35 GB/s
+ *     isutf8 unicode n=3193     543 ps/byte          1,795 mb/s
  *
  * This function considers all ASCII characters including NUL to be
  * valid UTF-8. The conditions for something not being valid are:
@@ -51,7 +49,7 @@ static const char kUtf8Dispatch[] = {
  *
  * @param size if -1 implies strlen
  */
-dontasan bool _isutf8(const void *data, size_t size) {
+dontasan bool isutf8(const void *data, size_t size) {
   long c;
   unsigned m;
   const char *p, *e;
@@ -61,6 +59,7 @@ dontasan bool _isutf8(const void *data, size_t size) {
   e = p + size;
   while (p < e) {
 #if defined(__x86_64__) && !defined(__chibicc__)
+    typedef char xmm_t __attribute__((__vector_size__(16), __aligned__(16)));
     if (!((intptr_t)p & 15)) {
       for (;;) {
         if ((m = __builtin_ia32_pmovmskb128(*(xmm_t *)p >= (xmm_t){0}) ^
diff --git a/libc/str/str.h b/libc/str/str.h
index 8d3dcb466..071653de4 100644
--- a/libc/str/str.h
+++ b/libc/str/str.h
@@ -11,6 +11,8 @@
 #define chomp16       _chomp16
 #define wchomp        _wchomp
 #define tpenc         _tpenc
+#define isutf8        _isutf8
+#define istext        _istext
 #define startswith    _startswith
 #define startswithi   _startswithi
 #define endswith      _endswith
@@ -187,9 +189,9 @@ wchar_t *wchomp(wchar_t *) libcesque;
 bool startswith(const char *, const char *) strlenesque;
 bool startswithi(const char *, const char *) strlenesque;
 bool endswith(const char *, const char *) strlenesque;
-bool _istext(const void *, size_t) libcesque;
-bool _isutf8(const void *, size_t) libcesque;
-char *strsignal_r(int, char[hasatleast 15]) returnsnonnull libcesque;
+bool istext(const void *, size_t) libcesque;
+bool isutf8(const void *, size_t) libcesque;
+char *strsignal_r(int, char[15]) returnsnonnull libcesque dontdiscard;
 int strerror_wr(int, uint32_t, char *, size_t)
 dontthrow nocallback;
 char16_t *chomp16(char16_t *) libcesque;
diff --git a/libc/sysv/consts.sh b/libc/sysv/consts.sh
index eeadf5ad9..8902cb3d3 100755
--- a/libc/sysv/consts.sh
+++ b/libc/sysv/consts.sh
@@ -185,30 +185,28 @@ syscon	open	O_CREAT					0x00000040		0x00000040		0x00000200		0x00000200		0x000002
 syscon	open	O_EXCL					0x00000080		0x00000080		0x00000800		0x00000800		0x00000800		0x00000800		0x00000800		0x00000080		# bsd consensus & NT faked as Linux [SYNC libc/calls/open-nt.c]
 syscon	open	O_TRUNC					0x00000200		0x00000200		0x00000400		0x00000400		0x00000400		0x00000400		0x00000400		0x00000200		# bsd consensus & NT faked as Linux [SYNC libc/calls/open-nt.c]
 syscon	open	O_DIRECTORY				0x00010000		0x00004000		0x00100000		0x00100000		0x00020000		0x00020000		0x00200000		0x00010000		# useful hint on UNIX, but required on NT (see kNtFileFlagBackupSemantics) [SYNC libc/calls/open-nt.c]
-syscon	open	O_NOFOLLOW				0x00020000		0x00008000		0x00000100		0x00000100		0x00000100		0x00000100		0x00000100		0x00020000	       	# bsd consensus; kNtFileFlagOpenReparsePoint
-syscon	open	O_DIRECT				0x00004000		0x00010000		0			0			0x00010000		0			0x00080000		0x00004000		#  kNtFileFlagNoBuffering [SYNC libc/calls/open-nt.c]
-syscon	open	O_NDELAY				0x00000800		0x00000800		0x00000004		0x00000004		0x00000004		0x00000004		0x00000004		0x00000800		#  kNtFileFlagWriteThrough [SYNC libc/calls/open-nt.c]
-syscon	open	O_RANDOM				0			0			0			0			0			0			0			0x80000000		#  kNtFileFlagRandomAccess [SYNC libc/calls/open-nt.c]
-syscon	open	O_SEQUENTIAL				0			0			0			0			0			0			0			0x40000000		#  kNtFileFlagSequentialScan [SYNC libc/calls/open-nt.c]
-syscon	open	O_COMPRESSED				0			0			0			0			0			0			0			0x20000000		#  kNtFileAttributeCompressed [SYNC libc/calls/open-nt.c]
+syscon	open	O_NOFOLLOW				0x00020000		0x00008000		0x00000100		0x00000100		0x00000100		0x00000100		0x00000100		0x00020000	       	# don't follow symlinks in the final path component; bsd consensus; kNtFileFlagOpenReparsePoint
+syscon	open	O_DIRECT				0x00004000		0x00010000		0xffffffff		0xffffffff		0x00010000		0xffffffff		0x00080000		0x00004000		# kNtFileFlagNoBuffering [SYNC libc/calls/open-nt.c]
+syscon	open	O_NONBLOCK				0x00000800		0x00000800		0x00000004		0x00000004		0x00000004		0x00000004		0x00000004		0x00000800		# same as O_NDELAY; overlaps with kNtFileFlagWriteThrough which we don't actually pass to win32 (we implement non-blocking ourselves using overlapped i/o)
+syscon	open	O_RANDOM				0			0			0			0			0			0			0			0x80000000		# kNtFileFlagRandomAccess [SYNC libc/calls/open-nt.c]
+syscon	open	O_SEQUENTIAL				0			0			0			0			0			0			0			0x40000000		# kNtFileFlagSequentialScan [SYNC libc/calls/open-nt.c]
+syscon	open	O_COMPRESSED				0			0			0			0			0			0			0			0x20000000		# kNtFileAttributeCompressed [SYNC libc/calls/open-nt.c]
 syscon	open	O_INDEXED				0			0			0			0			0			0			0			0x10000000		# !kNtFileAttributeNotContentIndexed [SYNC libc/calls/open-nt.c]
 syscon	open	O_CLOEXEC				0x00080000		0x00080000		0x01000000		0x01000000		0x00100000		0x00010000		0x00400000		0x00080000		# NT faked as Linux [SYNC libc/calls/open-nt.c]
 syscon	open	O_TMPFILE				0x00410000		0x00404000		0xffffffff		0xffffffff		0xffffffff		0xffffffff		0xffffffff		0xffffffff		# please use tmpfd(); Linux 3.11+ (c. 2013) __O_TMPFILE | O_DIRECTORY; kNtFileAttributeTemporary|kNtFileFlagDeleteOnClose [SYNC libc/calls/open-nt.c]
-syscon	open	O_SPARSE				0			0			0			0			0			0			0			0			# wut
-syscon	open	O_NONBLOCK				0x00000800		0x00000800		0x00000004		0x00000004		0x00000004		0x00000004		0x00000004		0x00000800		# bsd consensus
-syscon	open	O_ASYNC					0x00002000		0x00002000		0x00000040		0x00000040		0x00000040		0x00000040		0x00000040		0			# bsd consensus
-syscon	open	O_NOFOLLOW_ANY				0			0			0x20000000		0x20000000		0			0			0			0			#
-syscon	open	O_SYNC					0x00101000		0x00101000		0x00000080		0x00000080		0x00000080		0x00000080		0x00000080		0			# bsd consensus
+syscon	open	O_ASYNC					0x00002000		0x00002000		0x00000040		0x00000040		0x00000040		0x00000040		0x00000040		0xffffffff		# bsd consensus
+syscon	open	O_NOFOLLOW_ANY				0xffffffff		0xffffffff		0x20000000		0x20000000		0xffffffff		0xffffffff		0xffffffff		0xffffffff		# don't follow symlinks in any path component
+syscon	open	O_SYNC					0x00101000		0x00101000		0x00000080		0x00000080		0x00000080		0x00000080		0x00000080		0xffffffff		# bsd consensus
 syscon	open	O_NOCTTY				0x00000100		0x00000100		0x00020000		0x00020000		0x00008000		0x00008000		0x00008000		0			# used for remote viewing (default behavior on freebsd)
 syscon	open	O_NOATIME				0x00040000		0x00040000		0			0			0			0			0			0			# optimize away access time update
 syscon	open	O_EXEC					0x00200000		0x00200000		0			0x40000000		0x00040000		0			0x04000000		0			# open only for executing (POSIX.1 hack for when file mode is 0111); see fexecve(); O_PATH on Linux
-syscon	open	O_SEARCH				0			0			0			0x40100000		0x00040000		0			0x00800000		0			# it's specified by posix what does it mean
-syscon	open	O_DSYNC					0x00001000		0x00001000		0x00400000		0x00400000		0			0x00000080		0x00010000		0			#
-syscon	open	O_RSYNC					0x00101000		0x00101000		0			0			0			0x00000080		0x00020000		0			#
-syscon	open	O_PATH					0x00200000		0x00200000		0			0			0			0			0			0			# Linux 2.6.39+
-syscon	open	O_VERIFY				0			0			0			0			0x00200000		0			0			0			#
-syscon	open	O_SHLOCK				0			0			0x00000010		0x00000010		0x00000010		0x00000010		0x00000010		0			#
-syscon	open	O_EXLOCK				0			0			0x00000020		0x00000020		0x00000020		0x00000020		0x00000020		0			#
+syscon	open	O_SEARCH				0xffffffff		0xffffffff		0xffffffff		0x40100000		0x00040000		0xffffffff		0x00800000		0xffffffff		# it's specified by posix what does it mean
+syscon	open	O_DSYNC					0x00001000		0x00001000		0x00400000		0x00400000		0xffffffff		0x00000080		0x00010000		0xffffffff		#
+syscon	open	O_RSYNC					0x00101000		0x00101000		0xffffffff		0xffffffff		0xffffffff		0x00000080		0x00020000		0xffffffff		#
+syscon	open	O_PATH					0x00200000		0x00200000		0xffffffff		0xffffffff		0xffffffff		0xffffffff		0xffffffff		0xffffffff		# Linux 2.6.39+
+syscon	open	O_VERIFY				0xffffffff		0xffffffff		0xffffffff		0xffffffff		0x00200000		0xffffffff		0xffffffff		0xffffffff		#
+syscon	open	O_SHLOCK				0xffffffff		0xffffffff		0x00000010		0x00000010		0x00000010		0x00000010		0x00000010		0xffffffff		#
+syscon	open	O_EXLOCK				0xffffffff		0xffffffff		0x00000020		0x00000020		0x00000020		0x00000020		0x00000020		0xffffffff		#
 syscon	open	O_TTY_INIT				0			0			0			0			0x00080000		0			0			0			#
 syscon	compat	O_LARGEFILE				0x00008000		0x00020000		0			0			0			0			0			0			#
 
@@ -1047,7 +1045,7 @@ syscon	limits	MAX_INPUT				255			255			1024			1024			255			255			255			255			# w
 syscon	limits	SOMAXCONN				4096			4096			128			128			128			128			128			2147483647		# maximum backlog for listen()
 syscon	limits	_ARG_MAX				128*1024		128*1024		1024*1024		1024*1024		512*1024		512*1024		256*1024		32767*2			# bsd consensus
 syscon	limits	_NAME_MAX				255			255			255			255			255			255			511			255			# probably higher on windows?
-syscon	limits	_PATH_MAX				4096			4096			1024			1024			1024			1024			1024			512			# cosmopolitan libc imposes a lower 512 limit; nt theoretically goes up to 32767
+syscon	limits	_PATH_MAX				4096			4096			1024			1024			1024			1024			1024			32767			# win32 paths are 260 characters max. even with unc paths, cosmo wrappers won't go beyond 1024 chars
 syscon	limits	_NSIG					64			64			32			32			128			32			64			64			# _SIG_MAXSIG on FreeBSD
 
 #	unmount() flags
diff --git a/libc/sysv/consts/O_ASYNC.S b/libc/sysv/consts/O_ASYNC.S
index 969b3696e..c5ce8a9e9 100644
--- a/libc/sysv/consts/O_ASYNC.S
+++ b/libc/sysv/consts/O_ASYNC.S
@@ -1,2 +1,2 @@
 #include "libc/sysv/consts/syscon.internal.h"
-.syscon open,O_ASYNC,0x00002000,0x00002000,0x00000040,0x00000040,0x00000040,0x00000040,0x00000040,0
+.syscon open,O_ASYNC,0x00002000,0x00002000,0x00000040,0x00000040,0x00000040,0x00000040,0x00000040,0xffffffff
diff --git a/libc/sysv/consts/O_DIRECT.S b/libc/sysv/consts/O_DIRECT.S
index 3c6b195a6..457f71503 100644
--- a/libc/sysv/consts/O_DIRECT.S
+++ b/libc/sysv/consts/O_DIRECT.S
@@ -1,2 +1,2 @@
 #include "libc/sysv/consts/syscon.internal.h"
-.syscon open,O_DIRECT,0x00004000,0x00010000,0,0,0x00010000,0,0x00080000,0x00004000
+.syscon open,O_DIRECT,0x00004000,0x00010000,0xffffffff,0xffffffff,0x00010000,0xffffffff,0x00080000,0x00004000
diff --git a/libc/sysv/consts/O_DSYNC.S b/libc/sysv/consts/O_DSYNC.S
index b39c94e37..22e97a1d3 100644
--- a/libc/sysv/consts/O_DSYNC.S
+++ b/libc/sysv/consts/O_DSYNC.S
@@ -1,2 +1,2 @@
 #include "libc/sysv/consts/syscon.internal.h"
-.syscon open,O_DSYNC,0x00001000,0x00001000,0x00400000,0x00400000,0,0x00000080,0x00010000,0
+.syscon open,O_DSYNC,0x00001000,0x00001000,0x00400000,0x00400000,0xffffffff,0x00000080,0x00010000,0xffffffff
diff --git a/libc/sysv/consts/O_EXLOCK.S b/libc/sysv/consts/O_EXLOCK.S
index 84a182a10..19eb1b2f6 100644
--- a/libc/sysv/consts/O_EXLOCK.S
+++ b/libc/sysv/consts/O_EXLOCK.S
@@ -1,2 +1,2 @@
 #include "libc/sysv/consts/syscon.internal.h"
-.syscon open,O_EXLOCK,0,0,0x00000020,0x00000020,0x00000020,0x00000020,0x00000020,0
+.syscon open,O_EXLOCK,0xffffffff,0xffffffff,0x00000020,0x00000020,0x00000020,0x00000020,0x00000020,0xffffffff
diff --git a/libc/sysv/consts/O_NDELAY.S b/libc/sysv/consts/O_NDELAY.S
deleted file mode 100644
index cef260d32..000000000
--- a/libc/sysv/consts/O_NDELAY.S
+++ /dev/null
@@ -1,2 +0,0 @@
-#include "libc/sysv/consts/syscon.internal.h"
-.syscon open,O_NDELAY,0x00000800,0x00000800,0x00000004,0x00000004,0x00000004,0x00000004,0x00000004,0x00000800
diff --git a/libc/sysv/consts/O_NOFOLLOW_ANY.S b/libc/sysv/consts/O_NOFOLLOW_ANY.S
index e0eeb5aa5..522c528f0 100644
--- a/libc/sysv/consts/O_NOFOLLOW_ANY.S
+++ b/libc/sysv/consts/O_NOFOLLOW_ANY.S
@@ -1,2 +1,2 @@
 #include "libc/sysv/consts/syscon.internal.h"
-.syscon open,O_NOFOLLOW_ANY,0,0,0x20000000,0x20000000,0,0,0,0
+.syscon open,O_NOFOLLOW_ANY,0xffffffff,0xffffffff,0x20000000,0x20000000,0xffffffff,0xffffffff,0xffffffff,0xffffffff
diff --git a/libc/sysv/consts/O_PATH.S b/libc/sysv/consts/O_PATH.S
index 8d48cd6fe..4901c63ae 100644
--- a/libc/sysv/consts/O_PATH.S
+++ b/libc/sysv/consts/O_PATH.S
@@ -1,2 +1,2 @@
 #include "libc/sysv/consts/syscon.internal.h"
-.syscon open,O_PATH,0x00200000,0x00200000,0,0,0,0,0,0
+.syscon open,O_PATH,0x00200000,0x00200000,0xffffffff,0xffffffff,0xffffffff,0xffffffff,0xffffffff,0xffffffff
diff --git a/libc/sysv/consts/O_RSYNC.S b/libc/sysv/consts/O_RSYNC.S
index 79a6b45bf..41b324a8f 100644
--- a/libc/sysv/consts/O_RSYNC.S
+++ b/libc/sysv/consts/O_RSYNC.S
@@ -1,2 +1,2 @@
 #include "libc/sysv/consts/syscon.internal.h"
-.syscon open,O_RSYNC,0x00101000,0x00101000,0,0,0,0x00000080,0x00020000,0
+.syscon open,O_RSYNC,0x00101000,0x00101000,0xffffffff,0xffffffff,0xffffffff,0x00000080,0x00020000,0xffffffff
diff --git a/libc/sysv/consts/O_SEARCH.S b/libc/sysv/consts/O_SEARCH.S
index 1f5a47ab0..a710a8d1f 100644
--- a/libc/sysv/consts/O_SEARCH.S
+++ b/libc/sysv/consts/O_SEARCH.S
@@ -1,2 +1,2 @@
 #include "libc/sysv/consts/syscon.internal.h"
-.syscon open,O_SEARCH,0,0,0,0x40100000,0x00040000,0,0x00800000,0
+.syscon open,O_SEARCH,0xffffffff,0xffffffff,0xffffffff,0x40100000,0x00040000,0xffffffff,0x00800000,0xffffffff
diff --git a/libc/sysv/consts/O_SHLOCK.S b/libc/sysv/consts/O_SHLOCK.S
index 023b3f7d1..c3bc349fc 100644
--- a/libc/sysv/consts/O_SHLOCK.S
+++ b/libc/sysv/consts/O_SHLOCK.S
@@ -1,2 +1,2 @@
 #include "libc/sysv/consts/syscon.internal.h"
-.syscon open,O_SHLOCK,0,0,0x00000010,0x00000010,0x00000010,0x00000010,0x00000010,0
+.syscon open,O_SHLOCK,0xffffffff,0xffffffff,0x00000010,0x00000010,0x00000010,0x00000010,0x00000010,0xffffffff
diff --git a/libc/sysv/consts/O_SPARSE.S b/libc/sysv/consts/O_SPARSE.S
deleted file mode 100644
index 394087b29..000000000
--- a/libc/sysv/consts/O_SPARSE.S
+++ /dev/null
@@ -1,2 +0,0 @@
-#include "libc/sysv/consts/syscon.internal.h"
-.syscon open,O_SPARSE,0,0,0,0,0,0,0,0
diff --git a/libc/sysv/consts/O_SYNC.S b/libc/sysv/consts/O_SYNC.S
index 5d687d45d..758a09820 100644
--- a/libc/sysv/consts/O_SYNC.S
+++ b/libc/sysv/consts/O_SYNC.S
@@ -1,2 +1,2 @@
 #include "libc/sysv/consts/syscon.internal.h"
-.syscon open,O_SYNC,0x00101000,0x00101000,0x00000080,0x00000080,0x00000080,0x00000080,0x00000080,0
+.syscon open,O_SYNC,0x00101000,0x00101000,0x00000080,0x00000080,0x00000080,0x00000080,0x00000080,0xffffffff
diff --git a/libc/sysv/consts/O_VERIFY.S b/libc/sysv/consts/O_VERIFY.S
index 1063ddd83..60bd669a1 100644
--- a/libc/sysv/consts/O_VERIFY.S
+++ b/libc/sysv/consts/O_VERIFY.S
@@ -1,2 +1,2 @@
 #include "libc/sysv/consts/syscon.internal.h"
-.syscon open,O_VERIFY,0,0,0,0,0x00200000,0,0,0
+.syscon open,O_VERIFY,0xffffffff,0xffffffff,0xffffffff,0xffffffff,0x00200000,0xffffffff,0xffffffff,0xffffffff
diff --git a/libc/sysv/consts/_PATH_MAX.S b/libc/sysv/consts/_PATH_MAX.S
index 05633c754..63962ab57 100644
--- a/libc/sysv/consts/_PATH_MAX.S
+++ b/libc/sysv/consts/_PATH_MAX.S
@@ -1,2 +1,2 @@
 #include "libc/sysv/consts/syscon.internal.h"
-.syscon limits,_PATH_MAX,4096,4096,1024,1024,1024,1024,1024,512
+.syscon limits,_PATH_MAX,4096,4096,1024,1024,1024,1024,1024,32767
diff --git a/libc/sysv/consts/o.h b/libc/sysv/consts/o.h
index 35780fc41..efeb3cfcb 100644
--- a/libc/sysv/consts/o.h
+++ b/libc/sysv/consts/o.h
@@ -22,7 +22,6 @@ extern const unsigned O_EXEC;
 extern const unsigned O_EXLOCK;
 extern const unsigned O_INDEXED;
 extern const unsigned O_LARGEFILE;
-extern const unsigned O_NDELAY;
 extern const unsigned O_NOATIME;
 extern const unsigned O_NOCTTY;
 extern const unsigned O_NOFOLLOW;
@@ -34,7 +33,6 @@ extern const unsigned O_RSYNC;
 extern const unsigned O_SEARCH;
 extern const unsigned O_SEQUENTIAL;
 extern const unsigned O_SHLOCK;
-extern const unsigned O_SPARSE;
 extern const unsigned O_SYNC;
 extern const unsigned O_TMPFILE; /* use tmpfd() or tmpfile() */
 extern const unsigned O_TRUNC;
@@ -46,13 +44,12 @@ extern const unsigned O_VERIFY;
 #define O_CLOEXEC    O_CLOEXEC
 #define O_COMPRESSED O_COMPRESSED
 #define O_CREAT      O_CREAT
-#define O_DIRECT     O_DIRECT
 #define O_DIRECTORY  O_DIRECTORY
 #define O_EXCL       O_EXCL
 #define O_EXEC       O_EXEC
 #define O_INDEXED    O_INDEXED
 #define O_LARGEFILE  O_LARGEFILE
-#define O_NDELAY     O_NDELAY
+#define O_NDELAY     O_NONBLOCK
 #define O_NOATIME    O_NOATIME
 #define O_NOCTTY     O_NOCTTY
 #define O_NOFOLLOW   O_NOFOLLOW
diff --git a/libc/sysv/consts/sock.h b/libc/sysv/consts/sock.h
index 07b3aa882..ab3a6545e 100644
--- a/libc/sysv/consts/sock.h
+++ b/libc/sysv/consts/sock.h
@@ -18,6 +18,8 @@ extern const int SOCK_STREAM;
 #define SOCK_RAW       3
 #define SOCK_RDM       4
 #define SOCK_SEQPACKET 5
+#define SOCK_CLOEXEC   SOCK_CLOEXEC
+#define SOCK_NONBLOCK  SOCK_NONBLOCK
 
 COSMOPOLITAN_C_END_
 #endif /* !(__ASSEMBLER__ + __LINKER__ + 0) */
diff --git a/libc/sysv/dos2errno.sh b/libc/sysv/dos2errno.sh
index 36240fcac..c12e8995d 100755
--- a/libc/sysv/dos2errno.sh
+++ b/libc/sysv/dos2errno.sh
@@ -53,6 +53,7 @@ dos	kNtErrorInvalidAddress          EADDRNOTAVAIL
 dos	kNtErrorNotAReparsePoint	EINVAL
 dos	kNtErrorInvalidFunction         EINVAL
 dos	kNtErrorNegativeSeek		EINVAL
+dos	kNtErrorInvalidName		EINVAL
 dos	kNtErrorInvalidNetname          EADDRNOTAVAIL
 dos	kNtErrorInvalidUserBuffer	EMSGSIZE
 dos	kNtErrorIoPending		EINPROGRESS
diff --git a/libc/sysv/dos2errno/EINVAL.S b/libc/sysv/dos2errno/EINVAL.S
index 6947dd7a5..82a3ae4dc 100644
--- a/libc/sysv/dos2errno/EINVAL.S
+++ b/libc/sysv/dos2errno/EINVAL.S
@@ -14,4 +14,5 @@ kDos2Errno.EINVAL:
 	.e	kNtErrorNotAReparsePoint,EINVAL
 	.e	kNtErrorInvalidFunction,EINVAL
 	.e	kNtErrorNegativeSeek,EINVAL
+	.e	kNtErrorInvalidName,EINVAL
 	.e	WSAEINVAL,EINVAL
diff --git a/libc/testlib/testlib.h b/libc/testlib/testlib.h
index 606da71bb..071e6780c 100644
--- a/libc/testlib/testlib.h
+++ b/libc/testlib/testlib.h
@@ -12,7 +12,7 @@ COSMOPOLITAN_C_START_
  * Test cases are guaranteed by the linker to be run in order, sorted by
  * the (SUITE, NAME) tuple passed here.
  */
-#define TEST(SUITE, NAME)           \
+#define TEST(SUITE, NAME)             \
   __static_yoink("__testcase_start"); \
   __TEST_PROTOTYPE(SUITE, NAME, __TEST_ARRAY, )
 
@@ -25,7 +25,7 @@ COSMOPOLITAN_C_START_
  * temorarilly by the runtime while calling fixture functions. Fixtures
  * are also guaranteed by the linker to be run in sorted order.
  */
-#define FIXTURE(SUITE, NAME)       \
+#define FIXTURE(SUITE, NAME)         \
   __static_yoink("__fixture_start"); \
   __FIXTURE("fixture", SUITE, NAME)
 
@@ -36,7 +36,7 @@ COSMOPOLITAN_C_START_
  * Cartesian product of groups. That makes this similar to fixture, but
  * more appropriate for testing pure code (i.e. no syscalls) like math.
  */
-#define COMBO(GROUP, ENTRY)      \
+#define COMBO(GROUP, ENTRY)        \
   __static_yoink("__combo_start"); \
   __FIXTURE("combo", GROUP, ENTRY)
 
@@ -49,7 +49,7 @@ COSMOPOLITAN_C_START_
  *
  * @see EZBENCH()
  */
-#define BENCH(SUITE, NAME)       \
+#define BENCH(SUITE, NAME)         \
   __static_yoink("__bench_start"); \
   __TEST_PROTOTYPE(SUITE, NAME, __BENCH_ARRAY, optimizespeed)
 
@@ -223,11 +223,12 @@ void TearDownOnce(void);
 
 #define EXPECT_SYS(ERRNO, WANT, GOT, ...)                                  \
   do {                                                                     \
-    testlib_seterrno(0);                                                   \
+    int e = testlib_geterrno();                                            \
     __TEST_EQ(expect, __FILE__, __LINE__, __FUNCTION__, #WANT, #GOT, WANT, \
               GOT, __VA_ARGS__);                                           \
     __TEST_EQ(expect, __FILE__, __LINE__, __FUNCTION__, #ERRNO,            \
               testlib_strerror(), ERRNO, testlib_geterrno(), __VA_ARGS__); \
+    testlib_seterrno(e);                                                   \
   } while (0)
 
 #define EXPECT_FALSE(X) _TEST2("EXPECT_FALSE", false, ==, (X), #X, "", "", 0)
@@ -347,8 +348,6 @@ struct TestFixture {
 };
 
 extern char g_fixturename[256];
-extern char g_testlib_olddir[PATH_MAX];
-extern char g_testlib_tmpdir[PATH_MAX];
 extern bool g_testlib_shoulddebugbreak;     /* set by testmain */
 extern _Atomic(unsigned) g_testlib_ran;     /* set by wrappers */
 extern _Atomic(unsigned) g_testlib_failed;  /* set by wrappers */
diff --git a/libc/testlib/testrunner.c b/libc/testlib/testrunner.c
index 347ee0270..e4fe5dc3a 100644
--- a/libc/testlib/testrunner.c
+++ b/libc/testlib/testrunner.c
@@ -16,42 +16,27 @@
 │ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
-#include "libc/assert.h"
 #include "libc/calls/calls.h"
-#include "libc/calls/state.internal.h"
-#include "libc/calls/struct/sigaction.h"
-#include "libc/calls/struct/sigset.h"
 #include "libc/calls/syscall-sysv.internal.h"
 #include "libc/dce.h"
 #include "libc/errno.h"
-#include "libc/fmt/fmt.h"
 #include "libc/fmt/itoa.h"
-#include "libc/intrin/atomic.h"
 #include "libc/intrin/kprintf.h"
 #include "libc/intrin/strace.internal.h"
 #include "libc/intrin/weaken.h"
-#include "libc/log/check.h"
-#include "libc/log/internal.h"
+#include "libc/limits.h"
 #include "libc/macros.internal.h"
 #include "libc/nt/process.h"
-#include "libc/runtime/internal.h"
 #include "libc/runtime/runtime.h"
-#include "libc/runtime/symbols.internal.h"
-#include "libc/sock/sock.h"
+#include "libc/stdio/rand.h"
 #include "libc/stdio/stdio.h"
 #include "libc/str/str.h"
-#include "libc/sysv/consts/poll.h"
-#include "libc/sysv/consts/sa.h"
-#include "libc/sysv/consts/sig.h"
-#include "libc/sysv/consts/w.h"
 #include "libc/testlib/testlib.h"
 #include "libc/thread/thread.h"
 #include "libc/x/x.h"
 
-static int x;
-char g_testlib_olddir[PATH_MAX];
-char g_testlib_tmpdir[PATH_MAX];
-struct sigaction wanthandlers[31];
+static char g_olddir[PATH_MAX];
+static char g_tmpdir[PATH_MAX];
 static pthread_mutex_t testlib_error_lock;
 
 void testlib_finish(void) {
@@ -85,139 +70,64 @@ wontreturn void testlib_abort(void) {
 }
 
 static void SetupTmpDir(void) {
-  char *p = g_testlib_tmpdir;
-  p = stpcpy(p, kTmpPath);
-  p = stpcpy(p, program_invocation_short_name), *p++ = '.';
-  p = FormatInt64(p, getpid()), *p++ = '.';
-  p = FormatInt64(p, x++);
-  p[0] = '\0';
-  CHECK_NE(-1, makedirs(g_testlib_tmpdir, 0755), "%s", g_testlib_tmpdir);
-  CHECK_NOTNULL(realpath(g_testlib_tmpdir, g_testlib_tmpdir), "%`'s",
-                g_testlib_tmpdir);
-  CHECK_NE(-1, chdir(g_testlib_tmpdir), "%s", g_testlib_tmpdir);
+  char number[21];
+  FormatInt64(number, _rand64() & INT64_MAX);
+  g_tmpdir[0] = 0;
+  if (*kTmpPath != '/') {
+    strlcat(g_tmpdir, g_olddir, sizeof(g_tmpdir));
+    strlcat(g_tmpdir, "/", sizeof(g_tmpdir));
+  }
+  strlcat(g_tmpdir, kTmpPath, sizeof(g_tmpdir));
+  strlcat(g_tmpdir, program_invocation_short_name, sizeof(g_tmpdir));
+  strlcat(g_tmpdir, ".", sizeof(g_tmpdir));
+  strlcat(g_tmpdir, number, sizeof(g_tmpdir));
+  if (makedirs(g_tmpdir, 0755) || chdir(g_tmpdir)) {
+    perror(g_tmpdir);
+    exit(1);
+  }
 }
 
 static void TearDownTmpDir(void) {
-  CHECK_NE(-1, chdir(g_testlib_olddir));
-  CHECK_NE(-1, rmrf(g_testlib_tmpdir), "%s", g_testlib_tmpdir);
-}
-
-static void DoNothing(int sig) {
-  // function intentionally empty
-}
-
-static void CopySignalHandlers(void) {
-#if 0
-  int i;
-  for (i = 0; i < ARRAYLEN(wanthandlers); ++i) {
-    if (i + 1 == SIGKILL || i + 1 == SIGSTOP) continue;
-    CHECK_EQ(0, sigaction(i + 1, 0, wanthandlers + i), "sig=%d", i + 1);
+  if (chdir(g_olddir)) {
+    perror(g_olddir);
+    exit(1);
   }
-#endif
-}
-
-static void CheckSignalHandler(int sig) {
-#if 0
-  int i;
-  struct sigaction sa = {0};
-  unassert(0 <= sig - 1 && sig - 1 < ARRAYLEN(wanthandlers));
-  CHECK_EQ(0, sigaction(sig, 0, &sa));
-  CHECK_EQ(0, memcmp(wanthandlers + sig - 1, &sa, sizeof(sa)),
-           "signal handler for %s was %p/%#x/%#x:%x "
-           "but should have been restored to %p/%#x/%#x:%x",
-           strsignal(sig), sa.sa_handler, sa.sa_flags, sa.sa_mask.__bits[0],
-           sa.sa_mask.__bits[1], wanthandlers[sig - 1].sa_handler,
-           wanthandlers[sig - 1].sa_flags,
-           wanthandlers[sig - 1].sa_mask.__bits[0],
-           wanthandlers[sig - 1].sa_mask.__bits[1]);
-#endif
-}
-
-static void CheckForSignalHandlers(void) {
-#if 0
-  CheckSignalHandler(SIGINT);
-  CheckSignalHandler(SIGQUIT);
-  CheckSignalHandler(SIGCHLD);
-  CheckSignalHandler(SIGFPE);
-  CheckSignalHandler(SIGILL);
-  CheckSignalHandler(SIGSEGV);
-  CheckSignalHandler(SIGTRAP);
-  CheckSignalHandler(SIGABRT);
-  CheckSignalHandler(SIGBUS);
-  CheckSignalHandler(SIGSYS);
-  CheckSignalHandler(SIGWINCH);
-#endif
-}
-
-static void CheckForFileDescriptors(void) {
-#if 0
-  // TODO: race condition on fd cleanup :'(
-  int i;
-  struct pollfd pfds[16];
-  if (!_weaken(open) && !_weaken(socket)) return;
-  for (i = 0; i < ARRAYLEN(pfds); ++i) {
-    pfds[i].fd = i + 3;
-    pfds[i].events = POLLIN;
+  if (rmrf(g_tmpdir)) {
+    perror(g_tmpdir);
+    exit(1);
   }
-  if (poll(pfds, ARRAYLEN(pfds), 0) > 0) {
-    for (i = 0; i < ARRAYLEN(pfds); ++i) {
-      if (pfds[i].revents & POLLNVAL) continue;
-      ++g_testlib_failed;
-      kprintf("error: test failed to close() fd %d\n", pfds[i].fd);
-    }
-  }
-#endif
-}
-
-static void CheckForZombies(void) {
-#if 0
-  int e, pid;
-  sigset_t ss, oldss;
-  struct sigaction oldsa;
-  struct sigaction ignore = {.sa_handler = DoNothing};
-  if (!_weaken(fork)) return;
-  for (;;) {
-    if ((pid = wait(0)) == -1) {
-      CHECK_EQ(ECHILD, errno);
-      break;
-    } else {
-      ++g_testlib_failed;
-      kprintf("error: test failed to reap zombies %d\n", pid);
-    }
-  }
-#endif
 }
 
 /**
  * Runs all test case functions in sorted order.
  */
 void testlib_runtestcases(testfn_t *start, testfn_t *end, testfn_t warmup) {
-  /*
-   * getpid() calls are inserted to help visually see tests in traces
-   * which can be performed on Linux, FreeBSD, OpenBSD, and XNU:
-   *
-   *     strace -f o/default/test.com |& less
-   *     truss o/default/test.com |& less
-   *     ktrace -f trace o/default/test.com </dev/null; kdump -f trace | less
-   *     dtruss o/default/test.com |& less
-   *
-   * Test cases are iterable via a decentralized section. Your TEST()
-   * macro inserts .testcase.SUITENAME sections into the binary which
-   * the linker sorts into an array.
-   *
-   * @see ape/ape.lds
-   */
+  // getpid() calls are inserted to help visually see tests in traces
+  // which can be performed on Linux, FreeBSD, OpenBSD, and XNU:
+  //
+  //     strace -f o/default/test.com |& less
+  //     truss o/default/test.com |& less
+  //     ktrace -f trace o/default/test.com </dev/null; kdump -f trace | less
+  //     dtruss o/default/test.com |& less
+  //
+  // Test cases are iterable via a decentralized section. Your TEST()
+  // macro inserts .testcase.SUITENAME sections into the binary which
+  // the linker sorts into an array.
+  //
+  // @see ape/ape.lds
   const testfn_t *fn;
-  CopySignalHandlers();
   if (_weaken(testlib_enable_tmp_setup_teardown) ||
       _weaken(testlib_enable_tmp_setup_teardown_once)) {
-    CHECK_NOTNULL(getcwd(g_testlib_olddir, sizeof(g_testlib_olddir)));
+    if (!getcwd(g_olddir, sizeof(g_olddir))) {
+      perror("getcwd");
+      exit(1);
+    }
   }
   if (_weaken(testlib_enable_tmp_setup_teardown_once)) {
     SetupTmpDir();
   }
   if (_weaken(SetUpOnce)) _weaken(SetUpOnce)();
-  for (x = 0, fn = start; fn != end; ++fn) {
+  for (fn = start; fn != end; ++fn) {
     STRACE("");
     STRACE("# setting up %t", fn);
     if (_weaken(testlib_enable_tmp_setup_teardown)) SetupTmpDir();
@@ -237,9 +147,6 @@ void testlib_runtestcases(testfn_t *start, testfn_t *end, testfn_t warmup) {
     if (!IsWindows()) sys_getpid();
     if (_weaken(TearDown)) _weaken(TearDown)();
     if (_weaken(testlib_enable_tmp_setup_teardown)) TearDownTmpDir();
-    CheckForFileDescriptors();
-    CheckForSignalHandlers();
-    CheckForZombies();
   }
   if (_weaken(TearDownOnce)) {
     _weaken(TearDownOnce)();
diff --git a/libc/x/rmrf.c b/libc/x/rmrf.c
index 1f7a7524c..703be6649 100644
--- a/libc/x/rmrf.c
+++ b/libc/x/rmrf.c
@@ -17,10 +17,19 @@
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/calls/calls.h"
+#include "libc/dce.h"
 #include "libc/errno.h"
+#include "libc/stdio/ftw.h"
 #include "libc/sysv/errfuns.h"
 #include "libc/x/x.h"
-#include "libc/stdio/ftw.h"
+
+static inline bool IsSlash(char c) {
+  return c == '/' || c == '\\';
+}
+
+static inline int IsAlpha(int c) {
+  return ('A' <= c && c <= 'Z') || ('a' <= c && c <= 'z');
+}
 
 static int rmrf_callback(const char *fpath,      //
                          const struct stat *st,  //
@@ -48,6 +57,12 @@ static int rmrf_callback(const char *fpath,      //
  * @return 0 on success, or -1 w/ errno
  */
 int rmrf(const char *path) {
-  if (path[0] == '/' && !path[1]) return enotsup();
+  if ((IsSlash(path[0]) && !path[1]) ||
+      (IsWindows() && ((IsSlash(path[0]) && IsAlpha(path[1]) &&
+                        (!path[2] || (IsSlash(path[2]) && !path[3]))) ||
+                       (IsAlpha(path[0]) && path[1] == ':' &&
+                        (!path[2] || (IsSlash(path[2]) && !path[3])))))) {
+    return enotsup();  // if you really want rmrf("/") try rmrf("/.")
+  }
   return nftw(path, rmrf_callback, 128, FTW_PHYS | FTW_DEPTH);
 }
diff --git a/test/libc/calls/fcntl_test.c b/test/libc/calls/fcntl_test.c
index 1ded569e1..04cd818b1 100644
--- a/test/libc/calls/fcntl_test.c
+++ b/test/libc/calls/fcntl_test.c
@@ -65,8 +65,25 @@ TEST(fcntl_getfl, testRemembersAccessMode) {
   EXPECT_NE(-1, close(fd));
 }
 
-TEST(fcntl_setfl, testChangeAppendStatus) {
-  if (IsWindows()) return;  // Can't ReOpenFile() w/ O_APPEND
+TEST(fcntl_setfl, testChangeAppendStatus_proper) {
+  char buf[8] = {0};
+  ASSERT_SYS(0, 3, open("foo", O_CREAT | O_WRONLY, 0644));
+  // F_GETFL on XNU reports FWASWRITTEN (0x00010000) after write()
+  int old = fcntl(3, F_GETFL);
+  EXPECT_SYS(0, 3, write(3, "foo", 3));
+  EXPECT_SYS(0, 0, lseek(3, 0, SEEK_SET));
+  EXPECT_SYS(0, 0, fcntl(3, F_SETFL, old | O_APPEND));
+  EXPECT_SYS(0, 3, write(3, "bar", 3));
+  EXPECT_SYS(0, 0, lseek(3, 0, SEEK_SET));
+  EXPECT_SYS(0, 0, fcntl(3, F_SETFL, old));
+  EXPECT_SYS(0, 0, close(3));
+  ASSERT_SYS(0, 3, open("foo", 0));
+  EXPECT_SYS(0, 6, read(3, buf, 6));
+  EXPECT_STREQ("foobar", buf);
+  EXPECT_SYS(0, 0, close(3));
+}
+
+TEST(fcntl_setfl, testChangeAppendStatus_sloppy) {
   char buf[8] = {0};
   ASSERT_SYS(0, 3, open("foo", O_CREAT | O_WRONLY, 0644));
   EXPECT_SYS(0, 3, write(3, "foo", 3));
diff --git a/test/libc/calls/ioctl_test.c b/test/libc/calls/ioctl_test.c
index f667220ff..2707246ca 100644
--- a/test/libc/calls/ioctl_test.c
+++ b/test/libc/calls/ioctl_test.c
@@ -29,6 +29,7 @@
 #include "libc/sock/struct/ifreq.h"
 #include "libc/stdio/stdio.h"
 #include "libc/sysv/consts/af.h"
+#include "libc/sysv/consts/fio.h"
 #include "libc/sysv/consts/ipproto.h"
 #include "libc/sysv/consts/sio.h"
 #include "libc/sysv/consts/sock.h"
@@ -82,3 +83,18 @@ TEST(siocgifconf, mkntenvblock_systemroot) {
   EXITS(0);
 }
 #endif
+
+TEST(fionread, pipe) {
+  int pfds[2];
+  int pending;
+  ASSERT_SYS(0, 0, pipe(pfds));
+  ASSERT_SYS(0, 2, write(pfds[1], "hi", 2));
+  // checking the reading end is agreed upon
+  ASSERT_SYS(0, 0, ioctl(pfds[0], FIONREAD, &pending));
+  ASSERT_EQ(2, pending);
+  // checking the writing end is real hairy
+  // ASSERT_SYS(0, 0, ioctl(pfds[1], FIONREAD, &pending));
+  // ASSERT_EQ(2, pending);
+  ASSERT_SYS(0, 0, close(pfds[1]));
+  ASSERT_SYS(0, 0, close(pfds[0]));
+}
diff --git a/test/libc/calls/lseek_test.c b/test/libc/calls/lseek_test.c
index 59f22566f..9d6af1477 100644
--- a/test/libc/calls/lseek_test.c
+++ b/test/libc/calls/lseek_test.c
@@ -23,7 +23,11 @@
 #include "libc/limits.h"
 #include "libc/log/check.h"
 #include "libc/runtime/runtime.h"
+#include "libc/sock/sock.h"
+#include "libc/sysv/consts/af.h"
+#include "libc/sysv/consts/ipproto.h"
 #include "libc/sysv/consts/o.h"
+#include "libc/sysv/consts/sock.h"
 #include "libc/testlib/subprocess.h"
 #include "libc/testlib/testlib.h"
 #include "libc/x/x.h"
@@ -31,7 +35,7 @@
 char testlib_enable_tmp_setup_teardown;
 
 void SetUpOnce(void) {
-  ASSERT_SYS(0, 0, pledge("stdio rpath wpath cpath fattr proc", 0));
+  ASSERT_SYS(0, 0, pledge("stdio rpath wpath cpath fattr proc inet", 0));
 }
 
 TEST(lseek, ebadf) {
@@ -59,14 +63,26 @@ TEST(lseek, 64bit) {
   EXPECT_SYS(0, 0, close(3));
 }
 
-TEST(lseek, nonSeekableFd_espipe) {
+TEST(lseek, isPipe_ESPIPE) {
   int fds[2];
+  char buf[2];
   ASSERT_SYS(0, 0, pipe(fds));
   ASSERT_SYS(ESPIPE, -1, lseek(3, 0, SEEK_SET));
+  ASSERT_SYS(ESPIPE, -1, pwrite(4, "hi", 2, 0));
+  ASSERT_SYS(ESPIPE, -1, pread(3, buf, 2, 0));
   EXPECT_SYS(0, 0, close(4));
   EXPECT_SYS(0, 0, close(3));
 }
 
+TEST(lseek, isSocket_ESPIPE) {
+  char buf[2];
+  ASSERT_SYS(0, 3, socket(AF_INET, SOCK_STREAM, IPPROTO_TCP));
+  ASSERT_SYS(ESPIPE, -1, lseek(3, 0, SEEK_SET));
+  ASSERT_SYS(ESPIPE, -1, pwrite(3, "hi", 2, 0));
+  ASSERT_SYS(ESPIPE, -1, pread(3, buf, 2, 0));
+  EXPECT_SYS(0, 0, close(3));
+}
+
 TEST(lseek, filePositionChanges_areObservableAcrossDup) {
   ASSERT_SYS(0, 3, creat("wut", 0644));
   ASSERT_SYS(0, 4, dup(3));
diff --git a/test/libc/calls/open_test.c b/test/libc/calls/open_test.c
index fb3273a3a..5e448b01b 100644
--- a/test/libc/calls/open_test.c
+++ b/test/libc/calls/open_test.c
@@ -18,14 +18,20 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/calls/calls.h"
 #include "libc/calls/internal.h"
+#include "libc/calls/struct/stat.h"
 #include "libc/dce.h"
 #include "libc/errno.h"
 #include "libc/macros.internal.h"
 #include "libc/mem/gc.internal.h"
+#include "libc/runtime/runtime.h"
+#include "libc/stdio/stdio.h"
 #include "libc/str/str.h"
 #include "libc/sysv/consts/o.h"
 #include "libc/testlib/testlib.h"
 #include "libc/x/x.h"
+#include "libc/x/xasprintf.h"
+
+#define abs(rel) gc(xasprintf("%s/%s", gc(getcwd(0, 0)), rel))
 
 char testlib_enable_tmp_setup_teardown;
 
@@ -113,6 +119,7 @@ TEST(open, testOpenExistingForAppendWriteOnly_seeksToEnd) {
   char buf[16] = {0};
   ASSERT_SYS(0, 0, xbarf("hello.txt", "hell", -1));
   ASSERT_SYS(0, 3, open("hello.txt", O_WRONLY | O_APPEND));
+  EXPECT_SYS(EBADF, -1, pread(3, buf, 4, 0));  // in O_WRONLY mode
   EXPECT_SYS(0, 1, write(3, "o", 1));
   EXPECT_SYS(0, 0, lseek(3, 0, SEEK_SET));
   EXPECT_SYS(0, 1, write(3, "!", 1));
@@ -123,6 +130,50 @@ TEST(open, testOpenExistingForAppendWriteOnly_seeksToEnd) {
   EXPECT_SYS(0, 0, close(3));
 }
 
+TEST(open, appendRwMode_readsStartZero_writesAlwaysEof) {
+  char buf[8] = {0};
+  ASSERT_SYS(0, 0, xbarf("hello.txt", "hell", -1));
+  ASSERT_SYS(0, 3, open("hello.txt", O_RDWR | O_APPEND));
+  ASSERT_SYS(0, 2, read(3, buf, 2));
+  ASSERT_SYS(0, 2, read(3, buf + 2, 2));
+  EXPECT_STREQ("hell", buf);
+  EXPECT_SYS(0, 2, write(3, "o!", 2));
+  ASSERT_SYS(0, 6, pread(3, buf, 8, 0));
+  EXPECT_STREQ("hello!", buf);
+  EXPECT_SYS(0, 0, close(3));
+}
+
+TEST(open, appendReadOnlyMode_appendIsIgnored) {
+  char buf[8] = {0};
+  ASSERT_SYS(0, 0, xbarf("hello.txt", "hell", -1));
+  ASSERT_SYS(0, 3, open("hello.txt", O_RDONLY | O_APPEND));
+  EXPECT_SYS(EBADF, -1, write(3, "o!", 2));  // due to O_RDONLY
+  ASSERT_EQ(0, errno);
+  ASSERT_SYS(0, 2, read(3, buf, 2));
+  ASSERT_SYS(0, 2, read(3, buf + 2, 2));
+  EXPECT_STREQ("hell", buf);
+  ASSERT_SYS(0, 4, pread(3, buf, 4, 0));
+  EXPECT_SYS(0, 0, close(3));
+}
+
+TEST(open, truncReadWriteMode_getsTruncated) {
+  char buf[8] = {0};
+  ASSERT_FALSE(fileexists("hello.txt"));
+  ASSERT_SYS(ENOENT, -1, open("hello.txt", O_RDWR | O_TRUNC));
+  ASSERT_SYS(ENOENT, -1, open("hello.txt/there", O_RDWR | O_TRUNC));
+  ASSERT_SYS(0, 0, xbarf("hello.txt", "hell", -1));
+  ASSERT_SYS(ENOTDIR, -1, open("hello.txt/there", O_RDWR | O_TRUNC));
+  ASSERT_SYS(0, 3, open("hello.txt", O_RDWR | O_TRUNC));
+  ASSERT_SYS(0, 0, read(3, buf, 8));
+  EXPECT_STREQ("", buf);
+  ASSERT_SYS(0, 8, write(3, buf, 8));
+  EXPECT_SYS(0, 0, close(3));
+}
+
+TEST(open, truncReadOnlyMode_wontTruncate) {
+  ASSERT_SYS(EINVAL, -1, open("hello.txt", O_RDONLY | O_TRUNC));
+}
+
 TEST(open, testRelativePath_opensRelativeToDirFd) {
   ASSERT_SYS(0, 0, mkdir("foo", 0755));
   ASSERT_SYS(0, 3, open("foo", O_RDONLY | O_DIRECTORY));
@@ -132,6 +183,104 @@ TEST(open, testRelativePath_opensRelativeToDirFd) {
   EXPECT_SYS(0, 0, close(3));
 }
 
+TEST(open, eloop) {
+  ASSERT_SYS(0, 0, symlink("froot", "link"));
+  ASSERT_TRUE(issymlink("link"));
+  ASSERT_SYS(ELOOP, -1, open("link", O_RDONLY | O_NOFOLLOW));
+}
+
+TEST(open, norm) {
+  ASSERT_SYS(0, 0, mkdir("fun", 0755));
+  ASSERT_SYS(0, 0, mkdir("fun/house", 0755));
+  ASSERT_SYS(0, 0, touch("fun/house/norm", 0644));
+  ASSERT_SYS(0, 3, open("fun//house//norm", O_RDONLY));
+  ASSERT_SYS(0, 0, close(3));
+  ASSERT_SYS(0, 3, open(abs("fun//house//norm"), O_RDONLY));
+  ASSERT_SYS(0, 0, close(3));
+  ASSERT_SYS(0, 3, open("fun//house/./norm", O_RDONLY));
+  ASSERT_SYS(0, 0, close(3));
+  ASSERT_SYS(0, 3, open(abs("fun//house/./norm"), O_RDONLY));
+  ASSERT_SYS(0, 0, close(3));
+  ASSERT_SYS(0, 3, open("fun//house/../house/norm", O_RDONLY));
+  ASSERT_SYS(0, 0, close(3));
+  ASSERT_SYS(0, 3, open(abs("fun//house/../house/norm"), O_RDONLY));
+  ASSERT_SYS(0, 0, close(3));
+  ASSERT_SYS(ENOTDIR, -1, open("fun//house//norm/", O_RDONLY));
+  ASSERT_SYS(ENOTDIR, -1, open("fun//house//norm/.", O_RDONLY));
+  ASSERT_SYS(ENOTDIR, -1, open("fun//house//norm/./", O_RDONLY));
+  ASSERT_SYS(0, 3, open("fun//house//", O_RDONLY | O_DIRECTORY));
+  ASSERT_SYS(0, 0, close(3));
+}
+
+TEST(open, longNormDot) {
+#define NAME                                                                   \
+  "funfunfunfunfunfunfunfunfunfunfunfunfunfunfunfunfunfunfunfunfunfunfunfunfu" \
+  "nfunfunfunfunfunfunnfunfunfunfunfunfunnfunfunfunfunfunfununfunfunfunfunfun"
+  ASSERT_SYS(0, 0, mkdir(NAME, 0755));
+  ASSERT_SYS(0, 0, mkdir(abs(NAME "/" NAME), 0755));
+  ASSERT_SYS(0, 3, creat(abs(NAME "//" NAME "/./norm"), 0644));
+  ASSERT_TRUE(fileexists(abs(NAME "//" NAME "/norm")));
+  ASSERT_SYS(0, 0, close(3));
+}
+
+TEST(open, longNormDotDot) {
+#define NAME                                                                   \
+  "funfunfunfunfunfunfunfunfunfunfunfunfunfunfunfunfunfunfunfunfunfunfunfunfu" \
+  "nfunfunfunfunfunfunnfunfunfunfunfunfunnfunfunfunfunfunfununfunfunfunfunfun"
+  ASSERT_SYS(0, 0, mkdir(NAME, 0755));
+  ASSERT_SYS(0, 0, mkdir(abs(NAME "/" NAME), 0755));
+  ASSERT_SYS(0, 0, mkdir(abs(NAME "/" NAME "/" NAME), 0755));
+  ASSERT_SYS(0, 3, creat(abs(NAME "//" NAME "//" NAME "/../norm"), 0644));
+  ASSERT_TRUE(fileexists(abs(NAME "//" NAME "/norm")));
+  ASSERT_SYS(0, 0, close(3));
+}
+
+TEST(open, creat_directory) {
+  ASSERT_SYS(ENOENT, -1, open("fun", O_WRONLY | O_DIRECTORY));
+  ASSERT_FALSE(fileexists("fun"));
+  if (1) return;  // linux 5.15.122-0-lts creates file and returns error D:
+  ASSERT_SYS(ENOTDIR, -1, open("fun", O_CREAT | O_WRONLY | O_DIRECTORY, 0644));
+  ASSERT_TRUE(fileexists("fun"));
+}
+
+TEST(open, O_DIRECTORY_preventsOpeningRegularFiles) {
+  ASSERT_SYS(0, 0, touch("file", 0644));
+  ASSERT_SYS(ENOTDIR, -1, open("file", O_WRONLY | O_DIRECTORY));
+}
+
+TEST(open, O_DIRECTORY_isNotARequirementToOpenDirectory) {
+  ASSERT_SYS(0, 0, mkdir("dir", 0755));
+  ASSERT_SYS(0, 3, open("dir", O_RDONLY));
+  ASSERT_SYS(0, 0, close(3));
+}
+
+TEST(open, openExistingDirectoryForWriting_raisesError) {
+  ASSERT_SYS(0, 0, mkdir("dir", 0755));
+  ASSERT_SYS(EISDIR, -1, open("dir", O_WRONLY));
+}
+
+TEST(open, nameWithControlCode) {
+  if (IsWindows()) {
+    ASSERT_SYS(EINVAL, -1, touch("hi\1there", 0755));
+  } else {
+    ASSERT_SYS(0, 0, touch("hi\1there", 0755));
+  }
+}
+
+TEST(open, nameWithOverlongNul_doesntCreateTruncatedName) {
+  if (IsXnu() || IsWindows()) {
+    // XNU is the only one that thought to restrict this. XNU chose
+    // EILSEQ which makes the most sense. Linux says it'll raise EINVAL
+    // if invalid characters are detected. Not sure yet which characters
+    // those are. POSIX says nothing about invalid charaters in open.
+    ASSERT_SYS(EILSEQ, -1, touch("hi\300\200there", 0755));
+  } else {
+    ASSERT_SYS(0, 0, touch("hi\300\200there", 0755));
+    ASSERT_TRUE(fileexists("hi\300\200there"));
+    ASSERT_FALSE(fileexists("hi"));
+  }
+}
+
 int CountFds(void) {
   int i, count;
   for (count = i = 0; i < g_fds.n; ++i) {
@@ -154,3 +303,18 @@ TEST(open, lotsOfFds) {
     EXPECT_SYS(0, 0, close(i));
   }
 }
+
+static int64_t GetInode(const char *path) {
+  struct stat st;
+  ASSERT_SYS(0, 0, stat(path, &st));
+  return st.st_ino;
+}
+
+TEST(open, drive) {
+  if (!IsWindows()) return;
+  ASSERT_NE(GetInode("/"), GetInode("."));
+  ASSERT_EQ(GetInode("/"), GetInode("/c"));  // sorry you have to run on c:/
+  ASSERT_EQ(GetInode("/"), GetInode("/c/"));
+  ASSERT_SYS(0, 3, open("/", O_RDONLY));
+  ASSERT_SYS(0, 0, close(3));
+}
diff --git a/test/libc/calls/pledge_test.c b/test/libc/calls/pledge_test.c
index 7791a9d78..6c0a71ae0 100644
--- a/test/libc/calls/pledge_test.c
+++ b/test/libc/calls/pledge_test.c
@@ -447,7 +447,7 @@ TEST(pledge, open_rpath) {
   if (!pid) {
     ASSERT_SYS(0, 0, pledge("stdio rpath", 0));
     ASSERT_SYS(0, 3, open("foo", O_RDONLY));
-    ASSERT_SYS(EPERM, -1, open("foo", O_RDONLY | O_TRUNC));
+    ASSERT_SYS(EINVAL, -1, open("foo", O_RDONLY | O_TRUNC));
     ASSERT_SYS(EPERM, -1, open("foo", O_RDONLY | O_TMPFILE));
     ASSERT_SYS(EPERM, -1, open("foo", O_RDWR | O_TRUNC | O_CREAT, 0644));
     ASSERT_SYS(EPERM, -1, open("foo", O_WRONLY | O_TRUNC | O_CREAT, 0644));
diff --git a/test/libc/calls/readlinkat_test.c b/test/libc/calls/readlinkat_test.c
index 0aa59a71a..9589025e9 100644
--- a/test/libc/calls/readlinkat_test.c
+++ b/test/libc/calls/readlinkat_test.c
@@ -62,9 +62,6 @@ TEST(readlinkat, test) {
   EXPECT_EQ(255, buf[8] & 255);
   buf[8] = 0;
   EXPECT_STREQ("hello→", buf);
-  p = gc(xjoinpaths(g_testlib_tmpdir, "hello→"));
-  q = gc(realpath("there→", 0));
-  EXPECT_EQ(0, strcmp(p, q), "%`'s\n\t%`'s", p, q);
 }
 
 TEST(readlinkat, efault) {
@@ -89,10 +86,7 @@ TEST(readlinkat, frootloop) {
   ASSERT_SYS(0, 0, symlink("froot", "froot"));
   ASSERT_SYS(ELOOP, -1, readlink("froot/loop", buf, sizeof(buf)));
   if (O_NOFOLLOW) {
-    ASSERT_SYS(IsFreebsd()  ? EMLINK
-               : IsNetbsd() ? EFTYPE
-                            : ELOOP,
-               -1, open("froot", O_RDONLY | O_NOFOLLOW));
+    ASSERT_SYS(ELOOP, -1, open("froot", O_RDONLY | O_NOFOLLOW));
     if (0 && O_PATH) { /* need rhel5 test */
       ASSERT_NE(-1, (fd = open("froot", O_RDONLY | O_NOFOLLOW | O_PATH)));
       ASSERT_NE(-1, close(fd));
diff --git a/test/libc/calls/renameat_test.c b/test/libc/calls/renameat_test.c
index a5586888e..44c8554cc 100644
--- a/test/libc/calls/renameat_test.c
+++ b/test/libc/calls/renameat_test.c
@@ -17,7 +17,9 @@
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/calls/calls.h"
+#include "libc/dce.h"
 #include "libc/errno.h"
+#include "libc/runtime/runtime.h"
 #include "libc/sysv/consts/at.h"
 #include "libc/testlib/testlib.h"
 #include "libc/x/x.h"
@@ -42,18 +44,76 @@ TEST(renameat, enotdir) {
   // EXPECT_SYS(ENOTDIR, -1, rename("zoo", "yo/there"));
 }
 
+TEST(rename, eisdir) {
+  // new is a directory but old is not a directory
+  ASSERT_SYS(0, 0, mkdir("foo", 0755));
+  ASSERT_SYS(0, 0, touch("foo/bar", 0644));
+  ASSERT_SYS(0, 0, touch("lol", 0644));
+  ASSERT_SYS(EISDIR, -1, rename("lol", "foo"));
+}
+
+TEST(rename, enotdir) {
+  // old is a directory but new is not a directory
+  ASSERT_SYS(0, 0, mkdir("lol", 0755));
+  ASSERT_SYS(0, 0, touch("foo", 0644));
+  ASSERT_SYS(ENOTDIR, -1, rename("lol", "foo"));
+}
+
+TEST(rename, eisdir_again) {
+  // old is a directory but new is not a directory
+  ASSERT_SYS(0, 0, touch("foo", 0644));
+  ASSERT_SYS(0, 0, touch("bar", 0644));
+  ASSERT_SYS(ENOTDIR, -1, rename("foo/", "bar"));
+  ASSERT_SYS(ENOTDIR, -1, rename("foo", "bar/"));
+}
+
+TEST(rename, moveDirectoryOverDirectory_replacesOldDirectory) {
+  ASSERT_SYS(0, 0, mkdir("foo//", 0755));
+  ASSERT_SYS(0, 0, mkdir("lol", 0755));
+  ASSERT_SYS(0, 0, rename("lol", "foo"));
+  ASSERT_TRUE(fileexists("foo"));
+  ASSERT_FALSE(fileexists("lol"));
+}
+
+TEST(rename, enotempty) {
+  // POSIX specifies EEXIST or ENOTEMPTY when new path is non-empty dir.
+  // Old version of Linux (e.g. RHEL7) return EEXIST.
+  // Everything else returns ENOTEMPTY.
+  int rc;
+  ASSERT_SYS(0, 0, mkdir("foo", 0755));
+  ASSERT_SYS(0, 0, touch("foo/bar", 0644));
+  ASSERT_SYS(0, 0, mkdir("lol", 0755));
+  ASSERT_EQ(-1, (rc = rename("lol", "foo")));
+  ASSERT_TRUE(errno == ENOTEMPTY || errno == EEXIST);
+  errno = 0;
+}
+
+TEST(rename, moveIntoNonWritableDirectory_raisesEacces) {
+  // old versions of linux allow this
+  // new versions of linux report exdev?!
+  if (IsLinux()) return;
+  // netbsd and openbsd allow this
+  if (IsNetbsd() || IsOpenbsd()) return;
+  // windows doesn't really have permissions
+  if (IsWindows()) return;
+  // posix specifies this behavior
+  ASSERT_SYS(0, 0, mkdir("foo", 0111));
+  ASSERT_SYS(0, 0, touch("lol", 0644));
+  ASSERT_SYS(EACCES, -1, rename("lol", "foo/bar"));
+}
+
 TEST(renameat, testNull_returnsEfault) {
   ASSERT_SYS(0, 0, close(creat("hello", 0644)));
-  EXPECT_SYS(EFAULT, -1, renameat(AT_FDCWD, 0, AT_FDCWD, 0));
-  EXPECT_SYS(EFAULT, -1, renameat(AT_FDCWD, 0, AT_FDCWD, "hello"));
-  EXPECT_SYS(EFAULT, -1, renameat(AT_FDCWD, "hello", AT_FDCWD, 0));
+  ASSERT_SYS(EFAULT, -1, renameat(AT_FDCWD, 0, AT_FDCWD, 0));
+  ASSERT_SYS(EFAULT, -1, renameat(AT_FDCWD, 0, AT_FDCWD, "hello"));
+  ASSERT_SYS(EFAULT, -1, renameat(AT_FDCWD, "hello", AT_FDCWD, 0));
 }
 
 TEST(renameat, test) {
   ASSERT_SYS(0, 0, close(creat("first", 0644)));
-  EXPECT_TRUE(fileexists("first"));
-  EXPECT_TRUE(!fileexists("second"));
-  EXPECT_SYS(0, 0, renameat(AT_FDCWD, "first", AT_FDCWD, "second"));
-  EXPECT_TRUE(!fileexists("first"));
-  EXPECT_TRUE(fileexists("second"));
+  ASSERT_TRUE(fileexists("first"));
+  ASSERT_TRUE(!fileexists("second"));
+  ASSERT_SYS(0, 0, renameat(AT_FDCWD, "first", AT_FDCWD, "second"));
+  ASSERT_TRUE(!fileexists("first"));
+  ASSERT_TRUE(fileexists("second"));
 }
diff --git a/test/libc/calls/reservefd_test.c b/test/libc/calls/reservefd_test.c
index 42bffc8ae..7218e725a 100644
--- a/test/libc/calls/reservefd_test.c
+++ b/test/libc/calls/reservefd_test.c
@@ -25,6 +25,7 @@
 #include "libc/errno.h"
 #include "libc/macros.internal.h"
 #include "libc/runtime/internal.h"
+#include "libc/runtime/runtime.h"
 #include "libc/runtime/stack.h"
 #include "libc/stdio/rand.h"
 #include "libc/str/str.h"
@@ -66,13 +67,17 @@ TEST(reservefd, testGrowthOfFdsDataStructure) {
   int i, n;
   struct rlimit rlim;
   n = 1700;  // pe '2**16/40' → 1638 (likely value of g_fds.n)
-  if (!getrlimit(RLIMIT_NOFILE, &rlim)) n = MIN(n, rlim.rlim_cur - 3);
+  if (!getrlimit(RLIMIT_NOFILE, &rlim)) {
+    n = MIN(n, rlim.rlim_cur - 3);
+  } else {
+    errno = 0;
+  }
   for (i = 0; i < n; ++i) {
-    EXPECT_SYS(0, i + 3, open("/zip/usr/share/zoneinfo/UTC", O_RDONLY));
+    ASSERT_SYS(0, i + 3, open("/zip/usr/share/zoneinfo/UTC", O_RDONLY));
   }
   ASSERT_GT(g_fds.n, OPEN_MAX);
   for (i = 0; i < n; ++i) {
-    EXPECT_SYS(0, 0, close(i + 3));
+    ASSERT_SYS(0, 0, close(i + 3));
   }
 }
 
diff --git a/test/libc/calls/test.mk b/test/libc/calls/test.mk
index 538a7fd68..2d3029011 100644
--- a/test/libc/calls/test.mk
+++ b/test/libc/calls/test.mk
@@ -150,6 +150,7 @@ o/$(MODE)/test/libc/calls/zipread.com.zip.o: private			\
 o/$(MODE)/test/libc/calls/ioctl_test.com.runs:				\
 		private .PLEDGE =
 
+o/$(MODE)/test/libc/calls/lseek_test.com.runs				\
 o/$(MODE)/test/libc/calls/poll_test.com.runs:				\
 		private .PLEDGE = stdio rpath wpath cpath fattr proc inet
 
diff --git a/test/libc/calls/unlinkat_test.c b/test/libc/calls/unlinkat_test.c
index f194b3a05..328eb7ec8 100644
--- a/test/libc/calls/unlinkat_test.c
+++ b/test/libc/calls/unlinkat_test.c
@@ -20,6 +20,7 @@
 #include "libc/dce.h"
 #include "libc/errno.h"
 #include "libc/sysv/consts/at.h"
+#include "libc/sysv/consts/o.h"
 #include "libc/testlib/testlib.h"
 
 char testlib_enable_tmp_setup_teardown;
@@ -45,6 +46,16 @@ TEST(unlink, enotdir) {
   ASSERT_SYS(ENOTDIR, -1, unlink("o/doesnotexist"));
 }
 
+TEST(rmdir, willDeleteRegardlessOfAccessBits) {
+  ASSERT_SYS(0, 0, mkdir("foo", 0));
+  ASSERT_SYS(0, 0, rmdir("foo/"));
+}
+
+TEST(unlink, willDeleteRegardlessOfAccessBits) {
+  ASSERT_SYS(0, 0, touch("foo", 0));
+  ASSERT_SYS(0, 0, unlink("foo"));
+}
+
 TEST(unlinkat, test) {
   int i, fd;
   EXPECT_EQ(0, touch("mytmp", 0644));
diff --git a/test/libc/stdio/zipdir_test.c b/test/libc/stdio/zipdir_test.c
index b6ba5cb9b..4c1d42400 100644
--- a/test/libc/stdio/zipdir_test.c
+++ b/test/libc/stdio/zipdir_test.c
@@ -94,6 +94,7 @@ TEST(__zipos_normpath, vectors) {
       {"./", ""},
       {"..", ""},
       {"../", ""},
+      {"./foo/", "foo/"},
       {"foo/", "foo/"},
       {"../abc/def", "abc/def"},
       {"../abc/def/..", "abc/"},
diff --git a/test/libc/str/isutf8_test.c b/test/libc/str/isutf8_test.c
index fc90d0241..0f3a162e4 100644
--- a/test/libc/str/isutf8_test.c
+++ b/test/libc/str/isutf8_test.c
@@ -28,25 +28,24 @@
 
 void SetUpOnce(void) {
   GetSymbolTable();
-  ASSERT_SYS(0, 0, pledge("stdio rpath", 0));
 }
 
 TEST(isutf8, good) {
-  ASSERT_TRUE(_isutf8("\0\1\2\3", 4));
-  EXPECT_TRUE(_isutf8(kHyperion, kHyperionSize));
-  EXPECT_TRUE(_isutf8("𐌰𐌱𐌲𐌳𐌴𐌵𐌶𐌷▒▒▒▒▒▒▒▒▒▒▒▒", -1));
-  EXPECT_TRUE(_isutf8("天地玄黄 宇宙洪荒 日月盈昃 辰宿列张 寒来暑往 秋收冬藏"
-                      "闰馀成岁 律吕调阳 云腾致雨 露结为霜 金生丽水 玉出昆冈"
-                      "剑号巨阙 珠称夜光 果珍李柰 菜重芥姜 海咸河淡 鳞潜羽翔"
-                      "龙师火帝 鸟官人皇 始制文字 乃服衣裳 推位让国 有虞陶唐",
-                      -1));
+  ASSERT_TRUE(isutf8("\0\1\2\3", 4));
+  EXPECT_TRUE(isutf8(kHyperion, kHyperionSize));
+  EXPECT_TRUE(isutf8("𐌰𐌱𐌲𐌳𐌴𐌵𐌶𐌷▒▒▒▒▒▒▒▒▒▒▒▒", -1));
+  EXPECT_TRUE(isutf8("天地玄黄 宇宙洪荒 日月盈昃 辰宿列张 寒来暑往 秋收冬藏"
+                     "闰馀成岁 律吕调阳 云腾致雨 露结为霜 金生丽水 玉出昆冈"
+                     "剑号巨阙 珠称夜光 果珍李柰 菜重芥姜 海咸河淡 鳞潜羽翔"
+                     "龙师火帝 鸟官人皇 始制文字 乃服衣裳 推位让国 有虞陶唐",
+                     -1));
 }
 
 TEST(isutf8, bad) {
-  ASSERT_FALSE(_isutf8("\300\200", -1));              // overlong nul
-  ASSERT_FALSE(_isutf8("\200\300", -1));              // latin1 c1 control code
-  ASSERT_FALSE(_isutf8("\300\300", -1));              // missing continuation
-  ASSERT_FALSE(_isutf8("\377\200\200\200\200", -1));  // thompson-pike varint
+  ASSERT_FALSE(isutf8("\300\200", -1));              // overlong nul
+  ASSERT_FALSE(isutf8("\200\300", -1));              // latin1 c1 control code
+  ASSERT_FALSE(isutf8("\300\300", -1));              // missing continuation
+  ASSERT_FALSE(isutf8("\377\200\200\200\200", -1));  // thompson-pike varint
 }
 
 TEST(isutf8, oob) {
@@ -54,15 +53,15 @@ TEST(isutf8, oob) {
   char *p;
   for (n = 0; n < 32; ++n) {
     p = memset(malloc(n), 'a', n);
-    ASSERT_TRUE(_isutf8(p, n));
+    ASSERT_TRUE(isutf8(p, n));
     free(p);
   }
 }
 
 BENCH(isutf8, bench) {
-  EZBENCH_N("_isutf8", 0, _isutf8(0, 0));
-  EZBENCH_N("_isutf8", 5, _isutf8("hello", 5));
-  EZBENCH_N("_isutf8 ascii", kHyperionSize, _isutf8(kHyperion, kHyperionSize));
-  EZBENCH_N("_isutf8 unicode", kBlocktronicsSize,
-            _isutf8(kBlocktronics, kBlocktronicsSize));
+  EZBENCH_N("isutf8", 0, isutf8(0, 0));
+  EZBENCH_N("isutf8", 5, isutf8("hello", 5));
+  EZBENCH_N("isutf8 ascii", kHyperionSize, isutf8(kHyperion, kHyperionSize));
+  EZBENCH_N("isutf8 unicode", kBlocktronicsSize,
+            isutf8(kBlocktronics, kBlocktronicsSize));
 }
diff --git a/third_party/lua/luaencodeluadata.c b/third_party/lua/luaencodeluadata.c
index 92bdf8ee9..72efc26b8 100644
--- a/third_party/lua/luaencodeluadata.c
+++ b/third_party/lua/luaencodeluadata.c
@@ -192,7 +192,7 @@ static int SerializeString(lua_State *L, char **buf, int idx) {
   size_t i, n;
   const char *s;
   s = lua_tolstring(L, idx, &n);
-  utf8 = _isutf8(s, n);
+  utf8 = isutf8(s, n);
   RETURN_ON_ERROR(appendw(buf, '"'));
   for (i = 0; i < n; i++) {
     switch ((x = kLuaStrXlat[(c = s[i] & 255)])) {
diff --git a/third_party/sqlite3/shell.c b/third_party/sqlite3/shell.c
index 4cbd7d9e3..670e17fae 100644
--- a/third_party/sqlite3/shell.c
+++ b/third_party/sqlite3/shell.c
@@ -209,7 +209,7 @@ typedef unsigned char u8;
 #   define access(f,m) _access((f),(m))
 #  endif
 #  ifndef unlink
-#   define unlink _unlink
+#   define unlink_ _unlink
 #  endif
 #  ifndef strdup
 #   define strdup _strdup
diff --git a/tool/build/lib/elfwriter_zip.c b/tool/build/lib/elfwriter_zip.c
index 888026daa..caf29bc0e 100644
--- a/tool/build/lib/elfwriter_zip.c
+++ b/tool/build/lib/elfwriter_zip.c
@@ -163,8 +163,8 @@ void elfwriter_zip(struct ElfWriter *elf, const char *symbol, const char *cname,
   lfilehdrsize = kZipLfileHdrMinSize + namesize;
   crc = crc32_z(0, data, uncompsize);
   GetDosLocalTime(mtim.tv_sec, &mtime, &mdate);
-  if (_isutf8(name, namesize)) gflags |= kZipGflagUtf8;
-  if (S_ISREG(mode) && _istext(data, size)) {
+  if (isutf8(name, namesize)) gflags |= kZipGflagUtf8;
+  if (S_ISREG(mode) && istext(data, size)) {
     iattrs |= kZipIattrText;
   }
   dosmode = !(mode & 0200) ? kNtFileAttributeReadonly : 0;
diff --git a/tool/net/redbean.c b/tool/net/redbean.c
index 9518c499d..89ae726e9 100644
--- a/tool/net/redbean.c
+++ b/tool/net/redbean.c
@@ -1084,7 +1084,7 @@ static bool HasString(struct Strings *l, const char *s, size_t n) {
   return false;
 }
 
-static const char* DEFAULTLUAPATH = "/zip/.lua/?.lua;/zip/.lua/?/init.lua";
+static const char *DEFAULTLUAPATH = "/zip/.lua/?.lua;/zip/.lua/?/init.lua";
 
 static void UpdateLuaPath(const char *s) {
 #ifndef STATIC
@@ -1100,11 +1100,10 @@ static void UpdateLuaPath(const char *s) {
     if (t = strstr(curpath, DEFAULTLUAPATH)) {
       // if the DEFAULT path is found, prepend the path in front of it
       respath = xasprintf("%.*s%s/.lua/?.lua;%s/.lua/?/init.lua;%s",
-                          t-curpath, curpath, s, s, t);
+                          t - curpath, curpath, s, s, t);
     } else {
       // if the DEFAULT path is not found, append to the end
-      respath = xasprintf("%s;%s/.lua/?.lua;%s/.lua/?/init.lua",
-                          curpath, s, s);
+      respath = xasprintf("%s;%s/.lua/?.lua;%s/.lua/?/init.lua", curpath, s, s);
     }
     lua_pushstring(L, _gc(respath));
     lua_setfield(L, -3, "path");
@@ -3659,8 +3658,8 @@ static void StoreAsset(char *path, size_t pathlen, char *data, size_t datalen,
   }
   INFOF("(srvr) storing asset %`'s", path);
   disk = gflags = iattrs = 0;
-  if (_isutf8(path, pathlen)) gflags |= kZipGflagUtf8;
-  if (_istext(data, datalen)) iattrs |= kZipIattrText;
+  if (isutf8(path, pathlen)) gflags |= kZipGflagUtf8;
+  if (istext(data, datalen)) iattrs |= kZipIattrText;
   crc = crc32_z(0, data, datalen);
   if (datalen < 100) {
     method = kZipCompressionNone;