Make improvements

- Introduce ualarm() function
- Make rename() report EISEMPTY on Windows
- Always raise EINVAL upon open(O_RDONLY|O_TRUNC)
- Add macro so ./configure will detect SOCK_CLOEXEC
- Fix O_TRUNC without O_CREAT not working on Windows
- Let fcntl(F_SETFL) change O_APPEND status on Windows
- Make sure pwrite() / pread() report ESPIPE on sockets
- Raise ESPIPE on Windows when pwrite() is used on pipe
- Properly compute O_APPEND CreateFile() flags on Windows
- Don't require O_DIRECTORY to open directories on Windows
- Fix more instances of Windows reporting EISDIR and ENOTDIR
- Normalize EFTYPE and EMLINK to ELOOP on NetBSD and FreeBSD
- Make unlink() / rmdir() work on read-only files on Windows
- Validate UTF-8 on Windows paths to fix bug with overlong NUL
- Always print signal name to stderr when crashing due to SIG_DFL
- Fix Windows bug where denormalized paths >260 chars didn't work
- Block signals on BSDs when thread exits before trashing its own stack

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 {