Make important improvements

- Fix preadv() and pwritev() for old distros
- Introduce _npassert() and _unassert() macros
- Prove that file locks work properly on Windows
- Support fcntl(F_DUPFD_CLOEXEC) on more systems

test/libc/calls/lock_test.c

@@ -0,0 +1,186 @@
+/*-*- 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/struct/flock.h"
+#include "libc/dce.h"
+#include "libc/errno.h"
+#include "libc/intrin/kprintf.h"
+#include "libc/macros.internal.h"
+#include "libc/runtime/runtime.h"
+#include "libc/sysv/consts/f.h"
+#include "libc/sysv/consts/o.h"
+#include "libc/testlib/testlib.h"
+#include "libc/thread/thread.h"
+
+/**
+ * @fileoverview POSIX Advisory Locks Test
+ */
+
+#define PROCESSES  8
+#define THREADS    (IsWindows() ? 8 : 0)
+#define RATIO      3
+#define ITERATIONS 10
+
+char testlib_enable_tmp_setup_teardown;
+
+_Thread_local const char *kind;
+
+void Log(const char *fmt, ...) {
+#if 0
+  va_list va;
+  char b[512];
+  int i, n = sizeof(b);
+  va_start(va, fmt);
+  i = ksnprintf(b, n, "%s pid=%d tid=%d ", kind, getpid(), gettid());
+  i += kvsnprintf(b + i, MAX(0, n - i), fmt, va);
+  i += ksnprintf(b + i, MAX(0, n - i), "\n");
+  write(2, b, MIN(i, n));
+  va_end(va);
+#endif
+}
+
+void Lock(int fd, int type, long start, long len) {
+  int e;
+  struct flock lock = {
+      .l_type = type,
+      .l_whence = SEEK_SET,
+      .l_start = start,
+      .l_len = len,
+  };
+  e = errno;
+  while (fcntl(fd, F_SETLK, &lock)) {
+    ASSERT_TRUE(errno == EAGAIN || errno == EACCES);
+    errno = e;
+    Log("flock spinning on %d", fd);
+  }
+}
+
+void WriteLock(int fd, long start, long len) {
+  Lock(fd, F_WRLCK, start, len);
+  Log("acquired write lock on %d", fd);
+}
+
+void ReadLock(int fd, long start, long len) {
+  Lock(fd, F_RDLCK, start, len);
+  Log("acquired read lock on %d", fd);
+}
+
+void Unlock(int fd, long start, long len) {
+  Lock(fd, F_UNLCK, start, len);
+  Log("released lock on %d", fd);
+}
+
+void *Reader(void *arg) {
+  int i, j, fd;
+  char buf[10];
+  kind = arg;
+  ASSERT_NE(-1, (fd = open("db", O_RDONLY)));
+  for (j = 0; j < ITERATIONS; ++j) {
+    ReadLock(fd, 10, 10);
+    for (i = 0; i < 10; ++i) {
+      ASSERT_SYS(0, 1, pread(fd, buf + i, 1, 10 + i));
+      ASSERT_EQ(buf[0], buf[i]);
+    }
+    Unlock(fd, 10, 10);
+    sched_yield();
+  }
+  ASSERT_SYS(0, 0, close(fd));
+  return 0;
+}
+
+void *Writer(void *arg) {
+  int i, j, fd;
+  char buf[10];
+  kind = arg;
+  ASSERT_NE(-1, (fd = open("db", O_RDWR)));
+  for (j = 0; j < ITERATIONS; ++j) {
+    WriteLock(fd, 10, 10);
+    for (i = 0; i < 10; ++i) {
+      ASSERT_SYS(0, 1, pread(fd, buf + i, 1, 10 + i));
+      ASSERT_EQ(buf[0], buf[i]);
+    }
+    for (i = 0; i < 10; ++i) {
+      buf[i]++;
+    }
+    for (i = 0; i < 10; ++i) {
+      ASSERT_SYS(0, 1, pwrite(fd, buf + i, 1, 10 + i));
+    }
+    Unlock(fd, 10, 10);
+    sched_yield();
+  }
+  ASSERT_SYS(0, 0, close(fd));
+  return 0;
+}
+
+TEST(posixAdvisoryLocks, threadsAndProcessesFightingForLock) {
+  int i, rc, pid, fd, ws;
+  pthread_t th[THREADS + 1];
+
+  ASSERT_SYS(0, 3, creat("db", 0644));
+  ASSERT_SYS(0, 0, ftruncate(3, 30));
+  ASSERT_SYS(0, 0, close(3));
+
+  for (i = 0; i < THREADS; ++i) {
+    if (i % RATIO == 0) {
+      ASSERT_EQ(0, pthread_create(th + i, 0, Reader, "reader thread"));
+    } else {
+      ASSERT_EQ(0, pthread_create(th + i, 0, Writer, "writer thread"));
+    }
+  }
+
+  for (i = 0; i < PROCESSES; ++i) {
+    ASSERT_NE(-1, (rc = fork()));
+    if (!rc) {
+      if (i % RATIO == 0) {
+        Writer("writer process");
+      } else {
+        Reader("reader process");
+      }
+      _Exit(0);
+    }
+  }
+
+  ASSERT_NE(-1, (fd = open("db", O_RDWR)));
+  Lock(fd, F_WRLCK, 0, 10);
+  Lock(fd, F_WRLCK, 20, 10);
+
+  for (i = 0; i < THREADS; ++i) {
+    ASSERT_EQ(0, pthread_join(th[i], 0));
+  }
+
+  kind = "main process";
+  for (;;) {
+    int e = errno;
+    if ((pid = waitpid(0, &ws, 0)) != -1) {
+      if (WIFSIGNALED(ws)) {
+        Log("process %d terminated with %G", pid, WTERMSIG(ws));
+        testlib_incrementfailed();
+      } else if (WEXITSTATUS(ws)) {
+        Log("process %d exited with %d", pid, WEXITSTATUS(ws));
+        testlib_incrementfailed();
+      }
+    } else {
+      ASSERT_EQ(ECHILD, errno);
+      errno = e;
+      break;
+    }
+  }
+
+  ASSERT_SYS(0, 0, close(fd));
+}