openat (GNU Gnulib)

Gnulib module: openat

Portability problems fixed by Gnulib:

This function is missing on some platforms: glibc 2.3.6, Mac OS X 10.5, FreeBSD 6.0, NetBSD 5.0, OpenBSD 3.8, Minix 3.1.8, AIX 5.1, HP-UX 11, Cygwin 1.5.x, mingw, MSVC 14. But the replacement function is not safe to be used in libraries and is not multithread-safe.
Some platforms do not support O_CLOEXEC: AIX 7.1, Solaris 10.
Some platforms do not support O_DIRECTORY: glibc 2.0, Mac OS X 10.4, FreeBSD 7.4, NetBSD 4.0.1, OpenBSD 4.9, HP-UX 11, Solaris 10, Cygwin 1.5.x, mingw, MSVC 14.
On platforms where off_t is a 32-bit type, open may not work correctly with files 2 GiB and larger. See Large File Support.
This function does not fail when the file name argument ends in a slash and (without the slash) names a nonexistent file or a file that is not a directory, on some platforms: Solaris 9.

Portability problems not fixed by Gnulib:

The Gnulib replacement for O_CLOEXEC is not atomic, and so is not safe in the presence of multiple threads or signal handlers.
The Gnulib replacement for O_SEARCH may require read access instead of search/execute access.
On some platforms, O_SEARCH may reject directories where you have search access even though O_SEARCH is not replaced: macOS 12.6.
When the file does not exist, POSIX says the behavior of O_CREAT | O_DIRECTORY is unspecified. Most platforms fail with EINVAL in this case. However, in Linux kernels 6.3 and earlier, this function creates a regular file and then either returns successfully (Linux kernel 5.6 and earlier) or fails with ENOTDIR (Linux kernels 5.7–6.3).
openat (fd, "symlink", O_NOFOLLOW ...) fails with errno set to EMLINK instead of the POSIX-required ELOOP on some platforms: FreeBSD 10.1.
openat (fd, "symlink", O_NOFOLLOW ...) fails with errno set to EFTYPE instead of the POSIX-required ELOOP on some platforms: NetBSD 6.1.