Re: [PATCH] errno: make EEXIST != ENOTEMPTY on AIX

[Bruno Haible]

Hi Paul,

> * m4/calloc.m4 (gl_FUNC_CALLOC_GNU):
> * m4/malloc.m4 (gl_FUNC_MALLOC_GNU):
> * m4/realloc.m4 (gl_FUNC_REALLOC_GNU):
> * m4/scandir.m4 (gl_FUNC_SCANDIR):
> Define _LINUX_SOURCE_COMPAT, as this can sometimes help on AIX.
> * m4/errno_h.m4 (gl_HEADER_ERRNO_H):
> Define _LINUX_SOURCE_COMPAT, to make EEXIST != ENOTEMPTY.
> * m4/strerror_r.m4 (gl_FUNC_STRERROR_R):
> Define _LINUX_SOURCE_COMPAT, in case someone else does.

On AIX 7.1 (machine: gcc111.fsffrance.org), a testdir of the modules
  calloc-gnu malloc-gnu realloc-gnu scandir strerror_r-posix,
that previously passed all its tests, now has two test failures:


FAIL: test-error.sh
===================

--- /tmp/dkvt7aa        2024-08-01 03:35:10.000000000 -0700
+++ err2        2024-08-01 03:35:10.000000000 -0700
@@ -9,5 +9,5 @@
  hammer
  boing 123 is too large
  d2/bar.c:11: bark too loud
- test-error: can't steal: Permission denied
+ test-error: can't steal: Unknown system error
  test-error: fatal error
FAIL test-error.sh (exit status: 1)

FAIL: test-strerror_r
=====================

../../gltests/test-strerror_r.c:39: assertion 'buf[0] != '\0'' failed
FAIL test-strerror_r (exit status: 134)


A strerror_r function that, for EACCESS, returns "Unknown system error" instead
of "Permission denied", is pretty much completely unusable.

The cause is that our strerror_r replacement tests STRERROR_R_CHAR_P but then,
after a '#undef strerror_r' (which is necessary in order to avoid endless
recursion), uses the original strerror_r function, with return type 'int',
not 'char *'. The fix is to ignore STRERROR_R_CHAR_P there.

But then, the change to m4/strerror_r.m4 doesn't make sense either:
  - Regardless whether _LINUX_SOURCE_COMPAT is defined, strerror_r.c uses
    the original strerror_r function.
  - There is no reason to even ask for the glibc-compatible strerror_r,
    since the glibc strerror_r has been recognized as a mistake and gnulib
    therefore offers only a 'strerror_r-posix' module.

This patch fixes both issues.


2024-08-01  Bruno Haible  <bruno@clisp.org>

        strerror_r: Fix for AIX (regression yesterday).
        * lib/strerror_r.c: Ignore the value of STRERROR_R_CHAR_P on AIX.
        * m4/strerror_r.m4 (gl_FUNC_STRERROR_R): Don't define
        _LINUX_SOURCE_COMPAT, since it provides no advantage for strerror_r.

diff --git a/lib/strerror_r.c b/lib/strerror_r.c
index 0cd28ade6e..87fc114262 100644
--- a/lib/strerror_r.c
+++ b/lib/strerror_r.c
@@ -34,7 +34,7 @@
 
 #include "strerror-override.h"
 
-#if STRERROR_R_CHAR_P
+#if STRERROR_R_CHAR_P && !defined _AIX
 
 # if HAVE___XPG_STRERROR_R
 _GL_EXTERN_C int __xpg_strerror_r (int errnum, char *buf, size_t buflen);
@@ -159,7 +159,10 @@ strerror_r (int errnum, char *buf, size_t buflen)
     int ret;
     int saved_errno = errno;
 
-#if STRERROR_R_CHAR_P
+    /* Due to the '#undef strerror_r' above, on AIX, we're always using
+       the POSIX-compatible strerror_r function, regardless whether
+       _LINUX_SOURCE_COMPAT is defined or not.  */
+#if STRERROR_R_CHAR_P && !defined _AIX
 
     {
       ret = 0;
diff --git a/m4/strerror_r.m4 b/m4/strerror_r.m4
index eae9f1c419..5353972172 100644
--- a/m4/strerror_r.m4
+++ b/m4/strerror_r.m4
@@ -1,5 +1,5 @@
 # strerror_r.m4
-# serial 27
+# serial 28
 dnl Copyright (C) 2002, 2007-2024 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
@@ -10,13 +10,6 @@ AC_DEFUN([gl_FUNC_STRERROR_R]
   AC_REQUIRE([gl_STRING_H_DEFAULTS])
   AC_REQUIRE([gl_FUNC_STRERROR_R_WORKS])
 
-  dnl On AIX, ask for the GNU/Linux API.  Other modules might ask for
-  dnl that API for other reasons, so we will will need override it because
-  dnl we cannot easily ask AIX for the GNU/Linux API for everything
-  dnl but strerror_r.
-  AC_DEFINE([_LINUX_SOURCE_COMPAT], [1],
-    [Define so that AIX headers are more compatible with GNU/Linux.])
-
   dnl Some systems don't declare strerror_r() if _THREAD_SAFE and _REENTRANT
   dnl are not defined.
   AC_CHECK_DECLS_ONCE([strerror_r])