On 2026-06-25 03:27, Bruno Haible wrote:
The reason is that in this test program you pass fd = AT_FDCWD.
However, the crash in musl libc occurs only if fd>=0.
Oh! The light dawns. I installed the attached patch to Gnulib and
propagated it into GNU m4. The next CI run for m4 should test it.
Thanks.
From 3096dd735de70c4ba7b1a5210a1c9cde0ed3204d Mon Sep 17 00:00:00 2001
From: Paul Eggert <[email protected]>
Date: Thu, 25 Jun 2026 08:27:36 -0700
Subject: [PATCH] fstatat: port null file support to Alpine 3.24
Problem reported by Bruno Haible in:
https://lists.gnu.org/r/bug-gnulib/2026-06/msg00093.html
* m4/fstatat.m4 (gl_FUNC_FSTATAT): When checking for
support for a null pointer file, check nonnegative directory
file descriptors as well as AT_FDCWD.
---
ChangeLog | 9 +++++++++
m4/fstatat.m4 | 15 ++++++++++-----
2 files changed, 19 insertions(+), 5 deletions(-)
diff --git a/ChangeLog b/ChangeLog
index bf8784efa9..e0328ee95f 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,12 @@
+2026-06-25 Paul Eggert <[email protected]>
+
+ fstatat: port null file support to Alpine 3.24
+ Problem reported by Bruno Haible in:
+ https://lists.gnu.org/r/bug-gnulib/2026-06/msg00093.html
+ * m4/fstatat.m4 (gl_FUNC_FSTATAT): When checking for
+ support for a null pointer file, check nonnegative directory
+ file descriptors as well as AT_FDCWD.
+
2026-06-25 Bruno Haible <[email protected]>
manywarnings: Fix for compilers that are named '$host-gcc'.
diff --git a/m4/fstatat.m4 b/m4/fstatat.m4
index b706c891a4..34a1638e9b 100644
--- a/m4/fstatat.m4
+++ b/m4/fstatat.m4
@@ -1,5 +1,5 @@
# fstatat.m4
-# serial 7
+# serial 8
dnl Copyright (C) 2004-2026 Free Software Foundation, Inc.
dnl This file is free software; the Free Software Foundation
dnl gives unlimited permission to copy and/or distribute it,
@@ -68,7 +68,7 @@ AC_DEFUN([gl_FUNC_FSTATAT],
dnl is not present, and it is not worth the trouble to tune this.
AS_CASE([$REPLACE_FSTATAT],
[0],
- [AC_CACHE_CHECK([whether fstatat+AT_EMPTY_PATH allows null file],
+ [AC_CACHE_CHECK([for no AT_EMPTY_PATH or fstatat with null file],
[gl_cv_func_fstatat_null_file],
[AC_RUN_IFELSE(
[AC_LANG_PROGRAM(
@@ -85,9 +85,14 @@ AC_DEFUN([gl_FUNC_FSTATAT],
#endif
]],
[[struct stat st;
- return
- (AT_EMPTY_PATH
- && fstatat (AT_FDCWD, NULL, &st, AT_EMPTY_PATH) < 0);
+ if (!AT_EMPTY_PATH)
+ return 0; /* No need to replace fstatat. */
+ if (fstatat (AT_FDCWD, NULL, &st, AT_EMPTY_PATH) < 0)
+ return 1;
+ int fd = open (".", O_RDONLY);
+ if (fd < 0)
+ return 1; /* Play it safe. */
+ return fstatat (fd, NULL, &st, AT_EMPTY_PATH) < 0;
]])],
[gl_cv_func_fstatat_null_file=yes],
[gl_cv_func_fstatat_null_file=no],
--
2.53.0
