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/calls/dup3-sysv.c

@@ -19,18 +19,18 @@
 #include "libc/assert.h"
 #include "libc/calls/syscall-sysv.internal.h"
 #include "libc/calls/syscall_support-sysv.internal.h"
+#include "libc/cosmo.h"
 #include "libc/dce.h"
 #include "libc/errno.h"
 #include "libc/intrin/strace.internal.h"
 #include "libc/sysv/consts/o.h"
 #include "libc/sysv/errfuns.h"
-#include "libc/thread/thread.h"
 
 #define F_DUP2FD         10
 #define F_DUP2FD_CLOEXEC 18
 
 static struct Dup3 {
-  pthread_once_t once;
+  _Atomic(uint32_t) once;
   bool demodernize;
 } g_dup3;
 
@@ -58,7 +58,7 @@ int32_t sys_dup3(int32_t oldfd, int32_t newfd, int flags) {
     return __sys_fcntl(oldfd, how, newfd);
   }
 
-  pthread_once(&g_dup3.once, sys_dup3_test);
+  cosmo_once(&g_dup3.once, sys_dup3_test);
 
   if (!g_dup3.demodernize) {
     return __sys_dup3(oldfd, newfd, flags);