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

libc/intrin/unlockfileex.c

@@ -0,0 +1,50 @@
+/*-*- 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/syscall_support-nt.internal.h"
+#include "libc/errno.h"
+#include "libc/intrin/describeflags.internal.h"
+#include "libc/intrin/describentoverlapped.internal.h"
+#include "libc/intrin/strace.internal.h"
+#include "libc/nt/files.h"
+#include "libc/str/str.h"
+
+__msabi extern typeof(UnlockFileEx) *const __imp_UnlockFileEx;
+
+/**
+ * Unlocks file on the New Technology.
+ *
+ * @return handle, or -1 on failure
+ * @note this wrapper takes care of ABI, STRACE(), and __winerr()
+ */
+bool32 UnlockFileEx(int64_t hFile, uint32_t dwReserved,
+                    uint32_t nNumberOfBytesToUnlockLow,
+                    uint32_t nNumberOfBytesToUnlockHigh,
+                    struct NtOverlapped *lpOverlapped) {
+  bool32 ok;
+  STRACE("UnlockFileEx(%ld, %#x, %'zu, %s) → ...", hFile, dwReserved,
+         (uint64_t)nNumberOfBytesToUnlockHigh << 32 | nNumberOfBytesToUnlockLow,
+         DescribeNtOverlapped(lpOverlapped));
+  ok = __imp_UnlockFileEx(hFile, dwReserved, nNumberOfBytesToUnlockLow,
+                          nNumberOfBytesToUnlockHigh, lpOverlapped);
+  if (!ok) __winerr();
+  STRACE("UnlockFileEx(%ld, %#x, %'zu, [%s]) → %hhhd% m", hFile, dwReserved,
+         (uint64_t)nNumberOfBytesToUnlockHigh << 32 | nNumberOfBytesToUnlockLow,
+         DescribeNtOverlapped(lpOverlapped), ok);
+  return ok;
+}