Make improvements for Actually Portable Emacs

- Get SIGWINCH working again on the New Technology
- Correctly handle O_NOFOLLOW in open() on Windows
- Implement synthetic umask() functionality on Windows
- Do a better job managing file execute access on Windows
- Fill in `st_uid` and `st_gid` with username hash on Windows
- Munge UNICODE control pictures into control codes on Windows
- Do a better job ensuring Windows console settings are restored
- Introduce KPRINTF_LOG environment variable to log kprintf to a file

libc/calls/getuid.c

@@ -17,9 +17,11 @@
 │ PERFORMANCE OF THIS SOFTWARE.                                                │
 ╚─────────────────────────────────────────────────────────────────────────────*/
 #include "libc/assert.h"
+#include "libc/atomic.h"
 #include "libc/calls/calls.h"
 #include "libc/calls/syscall-sysv.internal.h"
 #include "libc/dce.h"
+#include "libc/intrin/atomic.h"
 #include "libc/intrin/strace.internal.h"
 #include "libc/limits.h"
 #include "libc/macros.internal.h"
@@ -27,7 +29,7 @@
 #include "libc/runtime/runtime.h"
 #include "libc/str/str.h"
 
-static uint32_t KnuthMultiplicativeHash32(const void *buf, size_t size) {
+static uint32_t __kmp32(const void *buf, size_t size) {
   size_t i;
   uint32_t h;
   const uint32_t kPhiPrime = 0x9e3779b1;
@@ -36,18 +38,24 @@ static uint32_t KnuthMultiplicativeHash32(const void *buf, size_t size) {
   return h;
 }
 
-static textwindows dontinline uint32_t GetUserNameHash(void) {
+textwindows uint32_t __synthesize_uid(void) {
   char16_t buf[257];
-  uint32_t size = ARRAYLEN(buf);
-  GetUserName(&buf, &size);
-  return KnuthMultiplicativeHash32(buf, size >> 1) & INT_MAX;
+  static atomic_uint uid;
+  uint32_t tmp, size = ARRAYLEN(buf);
+  if (!(tmp = atomic_load_explicit(&uid, memory_order_acquire))) {
+    GetUserName(&buf, &size);
+    tmp = __kmp32(buf, size >> 1) & INT_MAX;
+    if (!tmp) ++tmp;
+    atomic_store_explicit(&uid, tmp, memory_order_release);
+  }
+  return tmp;
 }
 
 /**
  * Returns real user id of process.
  *
  * This never fails. On Windows, which doesn't really have this concept,
- * we return a deterministic value that's likely to work.
+ * we return a hash of the username.
  *
  * @return user id (always successful)
  * @asyncsignalsafe
@@ -61,7 +69,7 @@ uint32_t getuid(void) {
   } else if (!IsWindows()) {
     rc = sys_getuid();
   } else {
-    rc = GetUserNameHash();
+    rc = __synthesize_uid();
   }
   npassert(rc >= 0);
   STRACE("%s() → %d", "getuid", rc);
@@ -72,7 +80,7 @@ uint32_t getuid(void) {
  * Returns real group id of process.
  *
  * This never fails. On Windows, which doesn't really have this concept,
- * we return a deterministic value that's likely to work.
+ * we return a hash of the username.
  *
  * @return group id (always successful)
  * @asyncsignalsafe
@@ -86,7 +94,7 @@ uint32_t getgid(void) {
   } else if (!IsWindows()) {
     rc = sys_getgid();
   } else {
-    rc = GetUserNameHash();
+    rc = __synthesize_uid();
   }
   npassert(rc >= 0);
   STRACE("%s() → %d", "getgid", rc);