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filesys.c: Fix readlink for ports on Darwin.

When passed a port, `readlink' relies on the Linux specific behavior of
empty c_path meaning "the fd itself".  That does not work on Darwin.
Since there is no branch that would yield both fd and c_path, fallback
to freadlink when __APPLE__ is defined.

* libguile/filesys.c (do_readlink): Call freadlink for !__APPLE__.
* configure.ac (AC_CHECK_FUNCS): Add freadlink.

Signed-off-by: Ludovic Courtès <ludo@gnu.org>
This commit is contained in:
Tomas Volf 2024-08-10 00:54:30 +02:00 committed by Ludovic Courtès
parent 21e3e1c420
commit 0ceb0036c3
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GPG key ID: 090B11993D9AEBB5
2 changed files with 12 additions and 3 deletions

View file

@ -556,7 +556,7 @@ AC_CHECK_FUNCS([DINFINITY DQNAN cexp chsize clog clog10 ctermid \
fstatat futimens openat \
sched_getaffinity sched_setaffinity sendfile pipe2 \
posix_spawn_file_actions_addclosefrom_np \
clearenv])
clearenv freadlink])
# The newlib C library uses _NL_ prefixed locale langinfo constants.
AC_CHECK_DECLS([_NL_NUMERIC_GROUPING], [], [], [[#include <langinfo.h>]])

View file

@ -1192,14 +1192,23 @@ SCM_DEFINE (scm_symlinkat, "symlinkat", 3, 0, 0,
#undef FUNC_NAME
#endif /* HAVE_SYMLINKAT */
/* Static helper function for choosing between readlink
/* Static helper function for choosing between readlink, freadlink,
and readlinkat. */
static int
do_readlink (int fd, const char *c_path, char *buf, size_t size)
{
#ifdef HAVE_READLINKAT
/* Darwin does not accept empty c_path. */
#if HAVE_READLINKAT && !__APPLE__
if (fd != -1)
return readlinkat (fd, c_path, buf, size);
#elif HAVE_FREADLINK
/* There is no branch in s_scm_readlink that would lead to having both
FD and non-empty C_PATH. Therefore if FD is set, we (on Darwin
only) use freadlink and ignore C_PATH. On Linux this case is
already handled by readlinkat, but Darwin does not understand empty
C_PATH to mean "the fd itself" the way Linux does. */
if (fd != -1)
return freadlink (fd, buf, size);
#else
(void) fd;
#endif