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faccessat: port to macOS (Bug#29231) macOS faccessat has the same bug that lstat does: if the file name ends in '/' it ignores the trailing slash. Problem reported for Emacs by Vincent Zhang. * doc/posix-functions/faccessat.texi (faccessat): Document this. * lib/faccessat.c (_GL_INCLUDING_UNISTD_H): Define and undef around the initial includes. Include errno.h, string.h, sys/stat.h. (orig_faccessat) [HAVE_FACCESSAT]: New function. Include "unistd.h" after defining it. (rpl_faccessat) [HAVE_FACCESSAT]: New implementation. * lib/unistd.in.h (faccessat) [REPLACE_FACCESSAT]: Handle in the usual way. * m4/faccessat.m4 (gl_FUNC_FACCESSAT): Replace faccessat if lstat dereferences symlinks, since faccessat is likely to have the same problem. * m4/unistd_h.m4 (gl_UNISTD_H_DEFAULTS): Default REPLACE_ACCESSAT. * modules/faccessat (Depends-on): Add fstatat. Depend if REPLACE_FACCESSAT is 1, too. (configure.ac): Link if REPLACE_FACCESSAT is 1. * modules/faccessat-tests (Depends-on): Add symlink. * modules/unistd (unistd.h): Substitute REPLACE_FACCESSAT. * tests/test-faccessat.c (main): Test for the bug.
author Paul Eggert <eggert@cs.ucla.edu>
date Sat, 11 Nov 2017 22:33:38 -0800
parents bfa05cb8159c
children 0f6b0bb3cee9
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@node faccessat
@section @code{faccessat}
@findex faccessat

POSIX specification:@* @url{http://www.opengroup.org/onlinepubs/9699919799/functions/faccessat.html}

Gnulib module: faccessat

Portability problems fixed by Gnulib:
@itemize
@item
This function is missing on some platforms:
glibc 2.3.6, macOS 10.12, FreeBSD 7.4, NetBSD 6.1.5, OpenBSD 4.9, Minix 3.1.8,
AIX 5.1, HP-UX 11, IRIX 6.5, OSF/1 5.1, Solaris 10, Cygwin 1.5.x, mingw, MSVC 14,
Interix 3.5, BeOS.
@item
On some platforms, @code{faccessat (dfd, "file/", amode, flag)}
succeeds instead of failing when @file{file} is not a directory.
macOS 10.13.
@end itemize

Portability problems not fixed by Gnulib:
@itemize
@item
The replacement does not always take ACLs into account.
@item
The replacement is not safe to be used in libraries.
@item
The replacement is not multithread-safe.
@item
The replacement does not support the @code{AT_SYMLINK_NOFOLLOW} flag,
which is supported by GNU @code{faccessat}.
@end itemize

Other problems of this function:
@itemize
@item
There is an inherent race between calling this function and performing
some action based on the results; you should think twice before trusting
this function, especially in a set-uid or set-gid program.
@end itemize