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Improve docs of more system calls

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This change also found a few POSIX compliance bugs with errnos. Another
bug was discovered where, on Windows, pread() and pwrite() could modify
the file position in cases where ReadFile() returned an error e.g. when
seeking past the end of file. We also have more tests!
This commit is contained in:
Justine Tunney 2022-10-02 22:14:33 -07:00
parent af24c19db3
commit ccbae7799e
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GPG key ID: BE714B4575D6E328
39 changed files with 589 additions and 175 deletions
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54
libc/calls/truncate.c
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@ -17,25 +17,65 @@
│ PERFORMANCE OF THIS SOFTWARE. │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "libc/calls/calls.h"
#include "libc/intrin/strace.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/sysv/errfuns.h"
#include "libc/zipos/zipos.internal.h"
/**
* Reduces or extends underlying physical medium of file.
* Changes size of file.
*
* If file was originally larger, content >length is lost.
* 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.
*
* @param path must exist
* @return 0 on success or -1 w/ errno
* 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 EFBIG or EINVAL if `length` is too huge
* @raise EFAULT if `path` points to invalid memory
* @raise ENOTSUP if `path` is a zip filesystem path
* @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 ENOENT if `path` doesn't exist or is an empty string
* @raise ETXTBSY if `path` is an executable being executed
* @raise EROFS if `path` is on a read-only filesystem
* @raise ENOSYS on bare metal
* @see ftruncate()
* @error ENOENT
* @threadsafe
*/
int truncate(const char *path, uint64_t length) {
int rc;
if (!IsWindows()) {
struct ZiposUri zipname;
if (IsMetal()) {
rc = enosys();
} else if (!path || (IsAsan() && !__asan_is_valid(path, 1))) {
rc = efault();
} else if (_weaken(__zipos_parseuri) &&
_weaken(__zipos_parseuri)(path, &zipname) != -1) {
rc = enotsup();
} 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);
}