mirror of
https://github.com/jart/cosmopolitan.git
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eeb20775d2
This will help C++ code that uses exceptions to be tinier. For example, this change shaves away 1000 lines of assembly code from LLVM's libcxx, which is 0.7% of all assembly instructions in the entire library.
244 lines
12 KiB
C
244 lines
12 KiB
C
/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
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│ vi: set et ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi │
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╞══════════════════════════════════════════════════════════════════════════════╡
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│ Copyright 2020 Justine Alexandra Roberts Tunney │
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│ │
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│ Permission to use, copy, modify, and/or distribute this software for │
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│ any purpose with or without fee is hereby granted, provided that the │
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│ above copyright notice and this permission notice appear in all copies. │
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│ │
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│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │
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│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │
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│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │
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│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │
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│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │
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│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │
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│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
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│ PERFORMANCE OF THIS SOFTWARE. │
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╚─────────────────────────────────────────────────────────────────────────────*/
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#include "libc/assert.h"
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#include "libc/calls/calls.h"
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#include "libc/calls/cp.internal.h"
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#include "libc/calls/internal.h"
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#include "libc/calls/state.internal.h"
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#include "libc/calls/syscall-nt.internal.h"
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#include "libc/calls/syscall-sysv.internal.h"
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#include "libc/dce.h"
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#include "libc/errno.h"
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#include "libc/fmt/itoa.h"
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#include "libc/intrin/asan.internal.h"
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#include "libc/intrin/describeflags.internal.h"
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#include "libc/intrin/strace.internal.h"
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#include "libc/intrin/weaken.h"
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#include "libc/log/log.h"
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#include "libc/runtime/zipos.internal.h"
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#include "libc/str/str.h"
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#include "libc/sysv/consts/at.h"
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#include "libc/sysv/consts/o.h"
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#include "libc/sysv/errfuns.h"
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/**
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* Opens file.
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*
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* Here's an example of how a file can be created:
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*
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* int fd = openat(AT_FDCWD, "hi.txt", O_CREAT | O_WRONLY | O_TRUNC, 0644);
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* write(fd, "hello\n", 6);
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* close(fd);
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*
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* Here's an example of how that file could read back into memory:
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*
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* char data[513] = {0};
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* int fd = openat(AT_FDCWD, "hi.txt", O_RDONLY);
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* read(fd, data, 512);
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* close(fd);
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* assert(!strcmp(data, "hello\n"));
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*
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* If your main() source file has this statement:
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*
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* __static_yoink("zipos");
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*
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* Then you can read zip assets by adding a `"/zip/..."` prefix to `path`, e.g.
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*
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* // run `zip program.com hi.txt` beforehand
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* openat(AT_FDCWD, "/zip/hi.txt", O_RDONLY);
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*
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* Cosmopolitan's general approach on Windows to path translation is to
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*
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* - replace `/' with `\`
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* - normalize `.' and `..`
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* - translate utf-8 into utf-16
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* - turn `"\X\foo"` into `"\\?\X:\foo"`
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* - turn `"\X"` into `"\\?\X:\"`
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* - turn `"X:\foo"` into `"\\?\X:\foo"`
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* - turn `"\\?\X:\foo"` back into `X:\foo` if less than 260 chars
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*
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* On Windows, opening files in `/tmp` will open them in GetTempPath(),
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* which is a secure per-user directory. Opening `/dev/tty` will open a
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* special console file descriptor holding both `CONIN$` and `CONOUT$`,
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* which can't be fully closed. Opening `/dev/null` will open up `NUL`.
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*
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* @param dirfd is normally `AT_FDCWD` but if it's an open directory and
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* `path` names a relative path then it's opened relative to `dirfd`
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* @param path is a UTF-8 string naming a filesystem entity
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* @param flags must have one of the following under the `O_ACCMODE` bits:
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* - `O_RDONLY` to open `path` for reading only
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* - `O_WRONLY` to open `path` for writing
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* - `O_RDWR` to open `path` for reading and writing
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* The following may optionally be bitwise or'd into `flags`:
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* - `O_CREAT` create file if it doesn't exist
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* - `O_TRUNC` automatic `ftruncate(fd,0)` if exists (atomic on unix)
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* - `O_CLOEXEC` automatic close() upon execve()
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* - `O_EXCL` exclusive access (see below)
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* - `O_APPEND` open file for appending only
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* - `O_NOFOLLOW` fail with ELOOP if it's a symlink
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* - `O_NONBLOCK` asks read/write to fail with `EAGAIN` rather than block
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* - `O_UNLINK` delete file automatically on close
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* - `O_EXEC` open file for execution only; see fexecve()
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* - `O_NOCTTY` prevents `path` from becoming the controlling terminal
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* - `O_DIRECTORY` advisory feature for avoiding accidentally opening files
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* - `O_DIRECT` it's complicated (not supported on Apple and OpenBSD)
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* - `O_DSYNC` it's complicated (zero on non-Linux/Apple)
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* - `O_RSYNC` it's complicated (zero on non-Linux/Apple)
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* - `O_VERIFY` it's complicated (zero on non-FreeBSD)
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* - `O_SHLOCK` it's complicated (zero on non-BSD)
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* - `O_EXLOCK` it's complicated (zero on non-BSD)
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* - `O_PATH` open only for metadata (Linux 2.6.39+ otherwise zero)
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* - `O_NOATIME` don't record access time (zero on non-Linux)
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* - `O_RANDOM` hint random access intent (zero on non-Windows)
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* - `O_SEQUENTIAL` hint sequential access intent (zero on non-Windows)
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* - `O_COMPRESSED` ask fs to abstract compression (zero on non-Windows)
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* - `O_INDEXED` turns on that slow performance (zero on non-Windows)
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* - `O_TMPFILE` EINVALs on non-Linux; please use tmpfd() / tmpfile()
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* There are three regular combinations for the above flags:
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* - `O_RDONLY`: Opens existing file for reading. If it doesn't
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* exist then nil is returned and errno will be `ENOENT` (or in
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* some other cases `ENOTDIR`).
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* - `O_WRONLY|O_CREAT|O_TRUNC`: Creates file. If it already
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* exists, then the existing copy is destroyed and the opened
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* file will start off with a length of zero. This is the
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* behavior of the traditional creat() system call.
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* - `O_WRONLY|O_CREAT|O_EXCL`: Create file only if doesn't exist
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* already. If it does exist then `nil` is returned along with
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* `errno` set to `EEXIST`.
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* @param mode is an octal user/group/other permission signifier that's
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* ignored if `O_CREAT` isn't passed in `flags`; when creating files
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* you'll usually want `mode` to be `0644` which enables global read
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* and only permits the owner to write; or when creating executables
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* you'll usually want `mode` to be `0755` which is the same, except
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* the executable bit is set thrice too
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* @return file descriptor (which needs to be close()'d), or -1 w/ errno
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* @raise EPERM if pledge() is in play w/o appropriate rpath/wpath/cpath
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* @raise EACCES if unveil() is in play and didn't unveil your `path` path
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* @raise EACCES if we don't have permission to search a component of `path`
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* @raise EACCES if file exists but requested `flags & O_ACCMODE` was denied
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* @raise EACCES if file doesn't exist and parent dir lacks write permissions
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* @raise EACCES if `O_TRUNC` was specified in `flags` but writing was denied
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* @raise ENOTSUP if `path` is on zip file system and `dirfd` isn't `AT_FDCWD`
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* @raise ENOEXEC if `path` is a zip path and this executable isn't a zip file
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* @raise ENOTDIR if a directory component in `path` exists as non-directory
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* @raise ENOTDIR if `path` ends with a trailing slash and refers to a file
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* @raise ENOTDIR if `path` is relative and `dirfd` isn't an open directory
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* @raise ENOTDIR if `path` isn't a directory and `O_DIRECTORY` was passed
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* @raise EILSEQ if `path` contains illegal UTF-8 sequences (Windows/MacOS)
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* @raise EROFS when writing is requested w/ `path` on read-only filesystem
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* @raise ENAMETOOLONG if symlink-resolved `path` length exceeds `PATH_MAX`
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* @raise ENAMETOOLONG if component in `path` exists longer than `NAME_MAX`
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* @raise ENAMETOOLONG if `path` is relative and longer than 260 characters
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* @raise ENOTSUP if `path` is on zip file system and process is vfork()'d
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* @raise ENOSPC if file system is full when `path` would be `O_CREAT`ed
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* @raise EINTR if we needed to block and a signal was delivered instead
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* @raise EEXIST if `O_CREAT|O_EXCL` are used and `path` already existed
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* @raise EINVAL if ASCII control codes are used in `path` on Windows
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* @raise EINVAL if `O_UNLINK` is used without `O_CREAT|O_EXCL`
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* @raise EINVAL if `O_TRUNC` is specified in `O_RDONLY` mode
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* @raise EINVAL if `flags` contains unsupported bits
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* @raise ECANCELED if thread was cancelled in masked mode
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* @raise ENOENT if `path` doesn't exist when `O_CREAT` isn't in `flags`
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* @raise ENOENT if `path` points to a string that's empty
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* @raise ENOMEM if insufficient memory was available
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* @raise EMFILE if process `RLIMIT_NOFILE` has been reached
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* @raise ENFILE if system-wide file limit has been reached
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* @raise EOPNOTSUPP if `path` names a named socket
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* @raise EFAULT if `path` points to invalid memory
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* @raise ETXTBSY if writing is requested on `path` that's being executed
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* @raise ELOOP if `flags` had `O_NOFOLLOW` and `path` is a symbolic link
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* @raise ELOOP if a loop was detected resolving components of `path`
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* @raise EISDIR if writing is requested and `path` names a directory
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* @cancelationpoint
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* @asyncsignalsafe
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* @restartable
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* @vforksafe
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*/
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int openat(int dirfd, const char *path, int flags, ...) {
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int rc;
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va_list va;
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unsigned mode;
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struct ZiposUri zipname;
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va_start(va, flags);
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mode = va_arg(va, unsigned);
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va_end(va);
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BEGIN_CANCELATION_POINT;
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if (!path || (IsAsan() && !__asan_is_valid_str(path))) {
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rc = efault();
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} else if ((flags & O_UNLINK) &&
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(flags & (O_CREAT | O_EXCL)) != (O_CREAT | O_EXCL)) {
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// O_UNLINK is a non-standard cosmo extension; we've chosen bits for
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// this magic number which we believe are unlikely to interfere with
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// the bits chosen by operating systems both today and in the future
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// however, due to the risks here and the irregularity of using this
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// feature for anything but temporary files, we are going to prevent
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// the clever use cases for now; please file an issue if you want it
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rc = einval();
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} else if (__isfdkind(dirfd, kFdZip)) {
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rc = enotsup(); // TODO
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} else if (_weaken(__zipos_open) &&
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_weaken(__zipos_parseuri)(path, &zipname) != -1) {
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if (!__vforked && dirfd == AT_FDCWD) {
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rc = _weaken(__zipos_open)(&zipname, flags);
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} else {
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rc = enotsup(); // TODO
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}
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} else if ((flags & O_ACCMODE) == O_RDONLY && (flags & O_TRUNC)) {
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// Every operating system we've tested (with the notable exception
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// of OpenBSD) will gladly truncate files opened in read-only mode
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rc = einval();
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} else if (IsLinux() || IsXnu() || IsFreebsd() || IsOpenbsd() || IsNetbsd()) {
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// openat unix userspace
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rc = sys_openat(dirfd, path, flags & ~O_UNLINK, mode);
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if (rc != -1) {
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// openat succeeded
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if (flags & O_UNLINK) {
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// Implement Cosmopolitan O_UNLINK extension for UNIX
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// This cannot fail since we require O_CREAT / O_EXCL
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unassert(!sys_unlinkat(dirfd, path, 0));
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}
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} else {
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// openat failed
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if (IsFreebsd() && errno == EMLINK) {
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// Address FreeBSD divergence from IEEE Std 1003.1-2008 (POSIX.1)
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// in the case when O_NOFOLLOW is used, but fails due to symlink.
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errno = ELOOP;
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}
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if (IsNetbsd() && errno == EFTYPE) {
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// Address NetBSD divergence from IEEE Std 1003.1-2008 (POSIX.1)
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// in the case when O_NOFOLLOW is used but fails due to symlink.
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errno = ELOOP;
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}
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}
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} else if (IsMetal()) {
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rc = sys_openat_metal(dirfd, path, flags, mode);
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} else if (IsWindows()) {
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rc = sys_open_nt(dirfd, path, flags, mode);
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} else {
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rc = enosys();
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}
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END_CANCELATION_POINT;
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STRACE("openat(%s, %#s, %s%s) → %d% m", DescribeDirfd(dirfd), path,
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DescribeOpenFlags(flags), DescribeOpenMode(flags, mode), rc);
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return rc;
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}
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__weak_reference(openat, openat64);
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