cosmopolitan/libc/calls/truncate.c
Justine Tunney ff77f2a6af
Make improvements
- This change fixes a bug that allowed unbuffered printf() output (to
  streams like stderr) to be truncated. This regression was introduced
  some time between now and the last release.

- POSIX specifies all functions as thread safe by default. This change
  works towards cleaning up our use of the @threadsafe / @threadunsafe
  documentation annotations to reflect that. The goal is (1) to use
  @threadunsafe to document functions which POSIX say needn't be thread
  safe, and (2) use @threadsafe to document functions that we chose to
  implement as thread safe even though POSIX didn't mandate it.

- Tidy up the clock_gettime() implementation. We're now trying out a
  cleaner approach to system call support that aims to maintain the
  Linux errno convention as long as possible. This also fixes bugs that
  existed previously, where the vDSO errno wasn't being translated
  properly. The gettimeofday() system call is now a wrapper for
  clock_gettime(), which reduces bloat in apps that use both.

- The recently-introduced improvements to the execute bit on Windows has
  had bugs fixed. access(X_OK) on a directory on Windows now succeeds.
  fstat() will now perform the MZ/#! ReadFile() operation correctly.

- Windows.h is no longer included in libc/isystem/, because it confused
  PCRE's build system into thinking Cosmopolitan is a WIN32 platform.
  Cosmo's Windows.h polyfill was never even really that good, since it
  only defines a subset of the subset of WIN32 APIs that Cosmo defines.

- The setlongerjmp() / longerjmp() APIs are removed. While they're nice
  APIs that are superior to the standardized setjmp / longjmp functions,
  they weren't superior enough to not be dead code in the monorepo. If
  you use these APIs, please file an issue and they'll be restored.

- The .com appending magic has now been removed from APE Loader.
2023-10-03 06:17:16 -07:00

89 lines
4.5 KiB
C

/*-*- 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 2020 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/cp.internal.h"
#include "libc/calls/syscall-nt.internal.h"
#include "libc/calls/syscall-sysv.internal.h"
#include "libc/dce.h"
#include "libc/errno.h"
#include "libc/intrin/asan.internal.h"
#include "libc/intrin/strace.internal.h"
#include "libc/intrin/weaken.h"
#include "libc/runtime/zipos.internal.h"
#include "libc/sysv/errfuns.h"
/**
* Changes size of file.
*
* If the file size is increased, the extended area shall appear as if
* it were zero-filled. If your file size is decreased, the extra data
* shall be lost.
*
* Some operating systems implement an optimization, where `length` is
* treated as a logical size and the requested physical space won't be
* allocated until non-zero values get written into it. Our tests show
* this happens on Linux (usually with 4096 byte granularity), FreeBSD
* (which favors 512-byte granularity), and MacOS (prefers 4096 bytes)
* however Windows, OpenBSD, and NetBSD always reserve physical space.
* This may be inspected using stat() then consulting stat::st_blocks.
*
* @param path is name of file that shall be resized
* @return 0 on success, or -1 w/ errno
* @raise EINVAL if `length` is negative
* @raise EINTR if signal was delivered instead
* @raise ECANCELED if thread was cancelled in masked mode
* @raise EFBIG or EINVAL if `length` is too huge
* @raise EFAULT if `path` points to invalid memory
* @raise EACCES if we don't have permission to search a component of `path`
* @raise ENOTDIR if a directory component in `path` exists as non-directory
* @raise ENAMETOOLONG if symlink-resolved `path` length exceeds `PATH_MAX`
* @raise ENAMETOOLONG if component in `path` exists longer than `NAME_MAX`
* @raise ELOOP if a loop was detected resolving components of `path`
* @raise EROFS if `path` is on a read-only filesystem (e.g. zip)
* @raise ENOENT if `path` doesn't exist or is an empty string
* @raise ETXTBSY if `path` is an executable being executed
* @raise ENOSYS on bare metal
* @cancellationpoint
* @see ftruncate()
*/
int truncate(const char *path, int64_t length) {
int rc;
struct ZiposUri zipname;
BEGIN_CANCELLATION_POINT;
if (IsMetal()) {
rc = enosys();
} else if (!path || (IsAsan() && !__asan_is_valid_str(path))) {
rc = efault();
} else if (_weaken(__zipos_parseuri) &&
_weaken(__zipos_parseuri)(path, &zipname) != -1) {
rc = erofs();
} else if (!IsWindows()) {
rc = sys_truncate(path, length, length);
if (IsNetbsd() && rc == -1 && errno == ENOSPC) {
errno = EFBIG; // POSIX doesn't specify ENOSPC for truncate()
}
} else {
rc = sys_truncate_nt(path, length);
}
END_CANCELLATION_POINT;
STRACE("truncate(%#s, %'ld) → %d% m", path, length, rc);
return rc;
}