Add shared memory apis to redbean

You can now do things like implement mutexes using futexes in your
redbean lua code. This provides the fastest possible inter-process
communication for your production systems when SQLite alone as ipc
or things like pipes aren't sufficient.

test/libc/intrin/lockipc_test.c

@@ -0,0 +1,92 @@
+/*-*- 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/errno.h"
+#include "libc/intrin/bits.h"
+#include "libc/intrin/intrin.h"
+#include "libc/intrin/kprintf.h"
+#include "libc/macros.internal.h"
+#include "libc/runtime/runtime.h"
+#include "libc/testlib/testlib.h"
+#include "libc/thread/thread.h"
+
+#define PROCESSES  8
+#define ITERATIONS 100000
+
+struct SharedMemory {
+  pthread_mutex_t mutex;
+  volatile long x;
+} * shm;
+
+void Worker(void) {
+  long t;
+  for (int i = 0; i < ITERATIONS; ++i) {
+    pthread_mutex_lock(&shm->mutex);
+    t = shm->x;
+    t += 1;
+    shm->x = t;
+    pthread_mutex_unlock(&shm->mutex);
+  }
+}
+
+TEST(lockipc, mutex) {
+  int e, rc, ws, pid;
+
+  // create shared memory
+  shm = _mapshared(FRAMESIZE);
+
+  // create shared mutex
+  pthread_mutexattr_t mattr;
+  pthread_mutexattr_init(&mattr);
+  pthread_mutexattr_settype(&mattr, PTHREAD_MUTEX_NORMAL);
+  pthread_mutexattr_setpshared(&mattr, PTHREAD_PROCESS_SHARED);
+  pthread_mutex_init(&shm->mutex, &mattr);
+  pthread_mutexattr_destroy(&mattr);
+
+  // create processes
+  for (int i = 0; i < PROCESSES; ++i) {
+    ASSERT_NE(-1, (rc = fork()));
+    if (!rc) {
+      Worker();
+      _Exit(0);
+    }
+  }
+
+  // wait for processes to finish
+  for (;;) {
+    e = errno;
+    if ((pid = waitpid(0, &ws, 0)) != -1) {
+      if (WIFSIGNALED(ws)) {
+        kprintf("process %d terminated with %G\n", pid, WTERMSIG(ws));
+        testlib_incrementfailed();
+      } else if (WEXITSTATUS(ws)) {
+        kprintf("process %d exited with %d\n", pid, WEXITSTATUS(ws));
+        testlib_incrementfailed();
+      }
+    } else {
+      ASSERT_EQ(ECHILD, errno);
+      errno = e;
+      break;
+    }
+  }
+
+  EXPECT_EQ(PROCESSES * ITERATIONS, shm->x);
+  ASSERT_EQ(0, pthread_mutex_destroy(&shm->mutex));
+  ASSERT_SYS(0, 0, munmap(shm, FRAMESIZE));
+}