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

net/https/getsslroots.c

@@ -18,11 +18,11 @@
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/calls/calls.h"
 #include "libc/calls/struct/dirent.h"
+#include "libc/cosmo.h"
 #include "libc/mem/mem.h"
 #include "libc/str/str.h"
 #include "libc/sysv/consts/dt.h"
 #include "libc/sysv/consts/o.h"
-#include "libc/thread/thread.h"
 #include "third_party/mbedtls/x509_crt.h"
 
 __static_yoink("ssl_root_support");
@@ -30,7 +30,7 @@ __static_yoink("ssl_root_support");
 #define SSL_ROOT_DIR "/zip/usr/share/ssl/root"
 
 static struct {
-  pthread_once_t once;
+  _Atomic(uint32_t) once;
   mbedtls_x509_crt chain;
 } g_ssl_roots;
 
@@ -74,6 +74,6 @@ static void InitSslRoots(void) {
  * Returns singleton of SSL roots stored in /zip/usr/share/ssl/root/...
  */
 mbedtls_x509_crt *GetSslRoots(void) {
-  pthread_once(&g_ssl_roots.once, InitSslRoots);
+  cosmo_once(&g_ssl_roots.once, InitSslRoots);
   return &g_ssl_roots.chain;
 }

net/https/sslcache.c

@@ -21,6 +21,7 @@
 #include "libc/calls/struct/stat.h"
 #include "libc/errno.h"
 #include "libc/intrin/bits.h"
+#include "libc/intrin/bsr.h"
 #include "libc/intrin/cmpxchg.h"
 #include "libc/intrin/safemacros.internal.h"
 #include "libc/log/check.h"
@@ -79,12 +80,16 @@ static struct SslCache *OpenSslCache(const char *path, size_t size) {
   return c;
 }
 
+static unsigned long rounddown2pow(unsigned long x) {
+  return x ? 1ul << _bsrl(x) : 0;
+}
+
 struct SslCache *CreateSslCache(const char *path, size_t bytes, int lifetime) {
   size_t ents, size;
   struct SslCache *c;
   if (!bytes) bytes = 10 * 1024 * 1024;
   if (lifetime <= 0) lifetime = 24 * 60 * 60;
-  ents = _rounddown2pow(MAX(2, bytes / sizeof(struct SslCacheEntry)));
+  ents = rounddown2pow(MAX(2, bytes / sizeof(struct SslCacheEntry)));
   size = sizeof(struct SslCache) + sizeof(struct SslCacheEntry) * ents;
   size = ROUNDUP(size, FRAMESIZE);
   c = OpenSslCache(path, size);