fchmodat (GNU Gnulib)

Gnulib module: fchmodat

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, Solaris 10, Cygwin 1.5.x, mingw, MSVC 14. But the replacement function is not safe to be used in libraries and is not multithread-safe.
This function does not fail when the file name argument ends in a slash and (without the slash) names a non-directory, on some platforms: AIX 7.2.
When given the AT_SYMLINK_NOFOLLOW flag, this function fails with errno set to ENOTSUP, even when the file is not a symbolic link: GNU/Linux with glibc 2.31, Cygwin 2.9.

Portability problems not fixed by Gnulib:

Some platforms do not allow changing the access bits on symbolic links.
If the AT_SYMLINK_NOFOLLOW flag is specified, this function can fail with errno set to EMFILE or ENFILE, and it fails with errno set to EOPNOTSUPP if the /proc file system is not mounted: GNU/Linux with glibc 2.34.
This function sometimes fails with EACCES when the failure is due to lack of appropriate privileges (EPERM), not to search permission denied on the file name prefix (EACCES): Linux kernel 5.15 with glibc 2.35 and a CIFS v1 file system (see https://bugs.gnu.org/65599).