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/ttyname.c

@@ -17,15 +17,26 @@
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/calls/calls.h"
+#include "libc/calls/sysparam.h"
+#include "libc/errno.h"
 #include "libc/log/log.h"
-
-static char ttyname_buf[PATH_MAX];
+#include "libc/paths.h"
 
 /**
  * Returns name of terminal.
+ *
+ * This function isn't required to be thread safe, consider ttyname_r().
+ *
+ * @return terminal path on success, or null w/ errno
+ * @see ttyname_r()
  */
 char *ttyname(int fd) {
-  int rc = ttyname_r(fd, ttyname_buf, sizeof(ttyname_buf));
-  if (rc != 0) return NULL;
-  return &ttyname_buf[0];
+  errno_t err;
+  static char buf[sizeof(_PATH_DEV) + MAXNAMLEN];
+  if (!(err = ttyname_r(fd, buf, sizeof(buf)))) {
+    return buf;
+  } else {
+    errno = err;
+    return 0;
+  }
 }