Make more fixes and improvements

- Remove PAGESIZE constant
- Fix realloc() documentation
- Fix ttyname_r() error reporting
- Make forking more reliable on Windows
- Make execvp() a few microseconds faster
- Make system() a few microseconds faster
- Tighten up the socket-related magic numbers
- Loosen restrictions on mmap() offset alignment
- Improve GetProgramExecutableName() with getenv("_")
- Use mkstemp() as basis for mktemp(), tmpfile(), tmpfd()
- Fix flakes in pthread_cancel_test, unix_test, fork_test
- Fix recently introduced futex stack overflow regression
- Let sockets be passed as stdio to subprocesses on Windows
- Improve security of bind() on Windows w/ SO_EXCLUSIVEADDRUSE

libc/sock/accept.c

@@ -23,13 +23,14 @@
  * Creates client socket file descriptor for incoming connection.
  *
  * @param fd is the server socket file descriptor
- * @param out_addr will receive the remote address
- * @param inout_addrsize provides and receives addr's byte length
+ * @param opt_out_addr will receive the remote address
+ * @param opt_inout_addrsize provides and receives addr's byte length
  * @return client fd which needs close(), or -1 w/ errno
  * @cancellationpoint
  * @asyncsignalsafe
  * @restartable (unless SO_RCVTIMEO)
  */
-int accept(int fd, struct sockaddr *out_addr, uint32_t *inout_addrsize) {
-  return accept4(fd, out_addr, inout_addrsize, 0);
+int accept(int fd, struct sockaddr *opt_out_addr,
+           uint32_t *opt_inout_addrsize) {
+  return accept4(fd, opt_out_addr, opt_inout_addrsize, 0);
 }

libc/sock/accept4.c

@@ -32,8 +32,8 @@
  * Creates client socket file descriptor for incoming connection.
  *
  * @param fd is the server socket file descriptor
- * @param out_addr will receive the remote address
- * @param inout_addrsize provides and receives out_addr's byte length
+ * @param opt_out_addr will receive the remote address
+ * @param opt_inout_addrsize provides and receives out_addr's byte length
  * @param flags can have SOCK_{CLOEXEC,NONBLOCK}, which may apply to
  *     both the newly created socket and the server one
  * @return client fd which needs close(), or -1 w/ errno
@@ -41,7 +41,7 @@
  * @asyncsignalsafe
  * @restartable (unless SO_RCVTIMEO)
  */
-int accept4(int fd, struct sockaddr *out_addr, uint32_t *inout_addrsize,
+int accept4(int fd, struct sockaddr *opt_out_addr, uint32_t *opt_inout_addrsize,
             int flags) {
   int rc;
   struct sockaddr_storage ss = {0};
@@ -61,11 +61,13 @@ int accept4(int fd, struct sockaddr *out_addr, uint32_t *inout_addrsize,
     if (IsBsd()) {
       __convert_bsd_to_sockaddr(&ss);
     }
-    __write_sockaddr(&ss, out_addr, inout_addrsize);
+    __write_sockaddr(&ss, opt_out_addr, opt_inout_addrsize);
   }
 
   END_CANCELLATION_POINT;
   STRACE("accept4(%d, [%s]) -> %d% lm", fd,
-         DescribeSockaddr(out_addr, inout_addrsize ? *inout_addrsize : 0), rc);
+         DescribeSockaddr(opt_out_addr,
+                          opt_inout_addrsize ? *opt_inout_addrsize : 0),
+         rc);
   return rc;
 }

libc/sock/bind-nt.c

@@ -17,15 +17,14 @@
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/assert.h"
+#include "libc/calls/struct/fd.internal.h"
 #include "libc/nt/winsock.h"
 #include "libc/sock/internal.h"
 #include "libc/sock/syscall_fd.internal.h"
-#include "libc/sock/yoink.inc"
-#include "libc/sysv/errfuns.h"
 
 textwindows int sys_bind_nt(struct Fd *fd, const void *addr,
                             uint32_t addrsize) {
-  npassert(fd->kind == kFdSocket);
+  unassert(fd->kind == kFdSocket);
   if (__sys_bind_nt(fd->handle, addr, addrsize) != -1) {
     return 0;
   } else {

libc/sock/bind.c

@@ -32,7 +32,11 @@
  *
  *     struct sockaddr_in in = {AF_INET, htons(12345), {htonl(0x7f000001)}};
  *     int fd = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
- *     bind(fd, &in, sizeof(in));
+ *     bind(fd, (struct sockaddr *)&in, sizeof(in));
+ *
+ * On Windows, Cosmopolitan's implementation of bind() takes care of
+ * always setting the WIN32-specific `SO_EXCLUSIVEADDRUSE` option on
+ * inet stream sockets in order to safeguard your servers from tests
  *
  * @param fd is the file descriptor returned by socket()
  * @param addr is usually the binary-encoded ip:port on which to listen

libc/sock/sockdebug.c

@@ -65,7 +65,7 @@ const char *(DescribeSockaddr)(char buf[128], const struct sockaddr *sa,
       unix = (const struct sockaddr_un *)sa;
       n = strnlen(unix->sun_path, sizeof(unix->sun_path));
       n = MIN(n, 128 - 1);
-      memcpy(buf, unix->sun_path, n);
+      if (n) memcpy(buf, unix->sun_path, n);
       buf[n] = 0;
     }
   }

libc/sock/socket-nt.c

@@ -16,14 +16,19 @@
 │ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/assert.h"
 #include "libc/calls/internal.h"
 #include "libc/calls/state.internal.h"
+#include "libc/errno.h"
+#include "libc/intrin/kprintf.h"
 #include "libc/mem/mem.h"
 #include "libc/nt/enum/fileflagandattributes.h"
 #include "libc/nt/iphlpapi.h"
 #include "libc/nt/winsock.h"
 #include "libc/sock/internal.h"
 #include "libc/sock/yoink.inc"
+#include "libc/str/str.h"
+#include "libc/sysv/consts/af.h"
 #include "libc/sysv/consts/ipproto.h"
 #include "libc/sysv/consts/o.h"
 #include "libc/sysv/consts/so.h"
@@ -42,13 +47,22 @@ __static_yoink("_dupsockfd");
 textwindows int sys_socket_nt(int family, int type, int protocol) {
   int64_t h;
   struct SockFd *sockfd;
-  int fd, oflags, truetype;
+  int fd, oflags, truetype, yes = 1;
   fd = __reservefd(-1);
   if (fd == -1) return -1;
   truetype = type & ~(SOCK_CLOEXEC | SOCK_NONBLOCK);
   if ((h = WSASocket(family, truetype, protocol, NULL, 0,
                      kNtWsaFlagOverlapped)) != -1) {
-    oflags = 0;
+
+    // sets SO_EXCLUSIVEADDRUSE on all sockets so they won't get pilfered
+    // you can read a blog post on this subject in the find_unused_port()
+    // pydoc of this file third_party/python/Lib/test/support/__init__.py
+    // this needs to happen right after socket is called or it won't work
+    if (family == AF_INET || family == AF_INET6) {
+      unassert(__sys_setsockopt_nt(h, SOL_SOCKET, -5, &yes, 4) != -1);
+    }
+
+    oflags = O_RDWR;
     if (type & SOCK_CLOEXEC) oflags |= O_CLOEXEC;
     if (type & SOCK_NONBLOCK) oflags |= O_NONBLOCK;
     sockfd = calloc(1, sizeof(struct SockFd));
@@ -62,6 +76,7 @@ textwindows int sys_socket_nt(int family, int type, int protocol) {
     g_fds.p[fd].handle = h;
     g_fds.p[fd].extra = (uintptr_t)sockfd;
     __fds_unlock();
+
     return fd;
   } else {
     __releasefd(fd);

libc/sock/socket.c

@@ -22,26 +22,31 @@
 #include "libc/sock/internal.h"
 #include "libc/sock/sock.h"
 #include "libc/sysv/consts/af.h"
+#include "libc/sysv/errfuns.h"
 
 /**
  * Creates new system resource for network communication, e.g.
  *
  *     int fd = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
  *
- * @param family can be AF_UNIX, AF_INET, etc.
+ * @param family can be AF_UNIX, AF_INET, AF_INET6, etc.
  * @param type can be SOCK_STREAM (for TCP), SOCK_DGRAM (e.g. UDP), or
  *     SOCK_RAW (IP) so long as IP_HDRINCL was passed to setsockopt();
  *     and additionally, may be or'd with SOCK_NONBLOCK, SOCK_CLOEXEC
  * @param protocol can be IPPROTO_TCP, IPPROTO_UDP, or IPPROTO_ICMP
  * @return socket file descriptor or -1 w/ errno
- * @error ENETDOWN, EPFNOSUPPORT, etc.
+ * @raise EAFNOSUPPORT if `family` isn't supported by system or platform
  * @see libc/sysv/consts.sh
  * @asyncsignalsafe
  */
 int socket(int family, int type, int protocol) {
   int rc;
-  if (family == AF_UNSPEC) family = AF_INET;
-  if (!IsWindows()) {
+  if (family == AF_UNSPEC) {
+    family = AF_INET;
+  }
+  if (family == -1) {
+    rc = eafnosupport();
+  } else if (!IsWindows()) {
     rc = sys_socket(family, type, protocol);
   } else {
     rc = sys_socket_nt(family, type, protocol);