Improve locks and signals

- Introduce fast spinlock API
- Double rand64() perf w/ spinlock
- Improve raise() on New Technology
- Support gettid() across platforms
- Implement SA_NODEFER on New Technology
- Move the lock intrinsics into LIBC_INTRIN
- Make SIGTRAP recoverable on New Technology
- Block SIGCHLD in wait4() on New Technology
- Add threading prototypes for XNU and FreeBSD
- Rewrite abort() fixing its minor bugs on XNU/NT
- Shave down a lot of the content in libc/bits/bits.h
- Let signal handlers modify CPU registers on New Technology

libc/calls/setpgid.c

@@ -0,0 +1,58 @@
+/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
+│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8                                :vi│
+╞══════════════════════════════════════════════════════════════════════════════╡
+│ Copyright 2022 Justine Alexandra Roberts Tunney                              │
+│                                                                              │
+│ Permission to use, copy, modify, and/or distribute this software for         │
+│ any purpose with or without fee is hereby granted, provided that the         │
+│ above copyright notice and this permission notice appear in all copies.      │
+│                                                                              │
+│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                │
+│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                │
+│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             │
+│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         │
+│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        │
+│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               │
+│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
+│ PERFORMANCE OF THIS SOFTWARE.                                                │
+╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/calls/calls.h"
+#include "libc/calls/internal.h"
+#include "libc/calls/strace.internal.h"
+#include "libc/dce.h"
+#include "libc/nt/console.h"
+#include "libc/sysv/errfuns.h"
+
+/**
+ * Changes process group for process.
+ */
+int setpgid(int pid, int pgid) {
+  int rc, me;
+  if (!IsWindows()) {
+    rc = sys_setpgid(pid, pgid);
+  } else {
+    me = getpid();
+    if (pid == me && pgid == me) {
+      /*
+       * "When a process is created with CREATE_NEW_PROCESS_GROUP
+       *  specified, an implicit call to SetConsoleCtrlHandler(NULL,TRUE)
+       *  is made on behalf of the new process; this means that the new
+       *  process has CTRL+C disabled. This lets shells handle CTRL+C
+       *  themselves, and selectively pass that signal on to
+       *  sub-processes. CTRL+BREAK is not disabled, and may be used to
+       *  interrupt the process/process group."
+       *                           ──Quoth MSDN § CreateProcessW()
+       */
+      if (SetConsoleCtrlHandler(0, 1)) {
+        rc = 0;
+      } else {
+        rc = __winerr();
+      }
+    } else {
+      // irregular use cases not supported on windows
+      rc = einval();
+    }
+  }
+  STRACE("setpgid(%d, %d) → %d% m", pid, pgid, rc);
+  return rc;
+}