Warning in lib/stdlib.c

Warning in lib/stdlib.c

[Eli Zaretskii]

Hi,

With the latest master branch, I get a compiler warning in stdlib.c
when building the unexec configuration:

  stdlib.c:20: warning: "_GL_STDLIB_INLINE" redefined
     20 | #define _GL_STDLIB_INLINE _GL_EXTERN_INLINE
	|
  In file included from ../src/conf_post.h:102,
		   from ../src/config.h:3763,
		   from stdlib.c:18:
  ./stdlib.h:136: note: this is the location of the previous definition
    136 | # define _GL_STDLIB_INLINE _GL_INLINE
	|

Re: Warning in lib/stdlib.c

[Paul Eggert]

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On 2024-12-21 05:10, Eli Zaretskii wrote:

>    stdlib.c:20: warning: "_GL_STDLIB_INLINE" redefined

That's a violation of the C standard and so should be fixed.

The real culprit here is that Emacs config.h includes <stdlib.h>. It's 
generally not a good idea for config.h to include headers like 
<stdlib.h>, as that's brittle (as shown here).

I adjusted Gnulib to work around this particular problem and merged that 
into Emacs. However, the culprit may cause other lurking issues so I 
also installed the attached patches to Emacs so that config.h no longer 
includes <stdlib.h>.

In <https://bugs.gnu.org/52455#21> I just now proposed removing 
no-longer-working code that attempts to support unexec on macOS. That 
would have simplified the attached patches.

It would also simplify things to remove the HYBRID_MALLOC code but I 
don't know whether that stuff is still used.

[-- Attachment #2: 0001-Let-Gnulib-deal-with-MB_CUR_MAX.patch --]
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From a51642ba5fad891239552fe7e746fa160e3f88ea Mon Sep 17 00:00:00 2001
From: Paul Eggert <eggert@cs.ucla.edu>
Date: Mon, 23 Dec 2024 14:03:06 -0800
Subject: [PATCH 1/2] Let Gnulib deal with MB_CUR_MAX

Recent Gnulib should work around the Android NDK 16
MB_CUR_MAX bug, so Emacs no longer needs to worry about it.
* configure.ac (gl_STDLIB_H):
Remove, to stop overriding Gnulib.
* configure.ac (__ctype_get_mb_cur_max)
(emacs_cv_broken_mb_cur_max, REPLACEMENT_MB_CUR_MAX):
* src/conf_post.h (MB_CUR_MAX):
Remove, as Gnulib does this now.
---
 configure.ac    | 33 ---------------------------------
 src/conf_post.h | 10 ----------
 2 files changed, 43 deletions(-)

diff --git a/configure.ac b/configure.ac
index 18cbb42b0ef..bfef9cd294d 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1615,10 +1615,6 @@ AC_DEFUN
 AC_DEFUN([gt_TYPE_WINT_T],
   [GNULIBHEADERS_OVERRIDE_WINT_T=0
    AC_SUBST([GNULIBHEADERS_OVERRIDE_WINT_T])])
-# Emacs does not need precise checks for the Solaris 10 MB_CUR_MAX bug.
-AC_DEFUN_ONCE([gl_STDLIB_H],
-  [AC_REQUIRE([gl_STDLIB_H_DEFAULTS])
-   gl_NEXT_HEADERS([stdlib.h])])
 # Emacs does not need to check for off64_t.
 AC_DEFUN([gl_TYPE_OFF64_T],
   [HAVE_OFF64_T=1
@@ -7646,35 +7642,6 @@ AC_DEFUN
 
 AC_SUBST([WINDOW_SYSTEM_OBJ])
 
-# Some systems have MB_CUR_MAX defined to a call to
-# __ctype_get_mb_cur_max, but do not have __ctype_get_mb_cur_max in
-# libc.  Check for that situation and define MB_CUR_MAX to something
-# sane.
-
-AC_CHECK_FUNC([__ctype_get_mb_cur_max])
-
-AC_CACHE_CHECK([whether MB_CUR_MAX is defined to function that won't link],
-  [emacs_cv_broken_mb_cur_max],
-  [AC_EGREP_CPP(__ctype_get_mb_cur_max, [
-#include <stdlib.h>
-#ifndef MB_CUR_MAX
-#define MB_CUR_MAX -1
-#endif
-static int foo = MB_CUR_MAX;
-], [AS_IF([test "$ac_cv_func___ctype_get_mb_cur_max" = "yes"],
-     [emacs_cv_broken_mb_cur_max=no],
-     [emacs_cv_broken_mb_cur_max=yes])],
-  [emacs_cv_broken_mb_cur_max=no])])
-
-AS_IF([test "$emacs_cv_broken_mb_cur_max" = "yes"],
- # Define this to 4, which is right for Android.
- [AS_CASE([$opsys], [android],
-   [AC_DEFINE([REPLACEMENT_MB_CUR_MAX], [4],
-      [Define to MB_CUR_MAX if stdlib.h is broken.])],
-   [AC_MSG_ERROR([MB_CUR_MAX does not work on your system.
-Please modify configure.ac to set an appropriate value, then
-send your change to bug-gnu-emacs@gnu.org])])])
-
 AH_TOP([/* GNU Emacs site configuration template file.
 
 Copyright (C) 1988-2024 Free Software Foundation, Inc.
diff --git a/src/conf_post.h b/src/conf_post.h
index 9d3f5711bef..6aa2c901cc7 100644
--- a/src/conf_post.h
+++ b/src/conf_post.h
@@ -462,16 +462,6 @@ #define VFORK() vfork ()
 # define UNINIT /* empty */
 #endif
 
-/* MB_CUR_MAX is often broken on systems which copy-paste LLVM
-   headers, so replace its definition with a working one if
-   necessary.  */
-
-#ifdef REPLACEMENT_MB_CUR_MAX
-#include <stdlib.h>
-#undef MB_CUR_MAX
-#define MB_CUR_MAX REPLACEMENT_MB_CUR_MAX
-#endif /* REPLACEMENT_MB_CUR_MAX */
-
 /* Emacs does not need glibc strftime behavior for AM and PM
    indicators.  */
 #define REQUIRE_GNUISH_STRFTIME_AM_PM false
-- 
2.45.2


[-- Attachment #3: 0002-Don-t-include-stdlib.h-from-conf_post.h.patch --]
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From 577714e3fe722625236ce060f53b5d76f7933454 Mon Sep 17 00:00:00 2001
From: Paul Eggert <eggert@cs.ucla.edu>
Date: Thu, 26 Dec 2024 15:44:34 -0800
Subject: [PATCH 2/2] =?UTF-8?q?Don=E2=80=99t=20include=20stdlib.h=20from?=
 =?UTF-8?q?=20conf=5Fpost.h?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

This is brittle, as evinced by the recent problem with lib/stdlib.c.
* src/conf_post.h: Move potential inclusion of stdlib.h and
redefinitions of malloc, free, realloc, aligned_alloc, and calloc
from here ...
* src/lisp.h: ... to here.  Do not redefine the symbols
if UNEXMACOS_C is defined.
* src/unexmacosx.c: Do not undef malloc, realloc, free.
(UNEXMACOS_C): New symbol, to prevent lisp.h from defining them.
---
 src/conf_post.h  | 49 ------------------------------------------------
 src/gmalloc.c    |  2 +-
 src/lisp.h       | 35 ++++++++++++++++++++++++++++++++++
 src/unexmacosx.c |  7 +------
 4 files changed, 37 insertions(+), 56 deletions(-)

diff --git a/src/conf_post.h b/src/conf_post.h
index 6aa2c901cc7..e204a85b973 100644
--- a/src/conf_post.h
+++ b/src/conf_post.h
@@ -93,55 +93,6 @@ Copyright (C) 1988, 1993-1994, 1999-2002, 2004-2024 Free Software
 # define ADDRESS_SANITIZER false
 #endif
 
-#ifdef emacs
-/* We include stdlib.h here, because Gnulib's stdlib.h might redirect
-   'free' to its replacement, and we want to avoid that in unexec
-   builds.  Including it here will render its inclusion after config.h
-   a no-op.  */
-# if (defined DARWIN_OS && defined HAVE_UNEXEC) || defined HYBRID_MALLOC
-#  include <stdlib.h>
-# endif
-#endif
-
-#if defined DARWIN_OS && defined emacs && defined HAVE_UNEXEC
-# undef malloc
-# define malloc unexec_malloc
-# undef realloc
-# define realloc unexec_realloc
-# undef free
-# define free unexec_free
-
-extern void *unexec_malloc (size_t);
-extern void *unexec_realloc (void *, size_t);
-extern void unexec_free (void *);
-
-#endif
-
-/* If HYBRID_MALLOC is defined (e.g., on Cygwin), emacs will use
-   gmalloc before dumping and the system malloc after dumping.
-   hybrid_malloc and friends, defined in gmalloc.c, are wrappers that
-   accomplish this.  */
-#ifdef HYBRID_MALLOC
-#ifdef emacs
-#undef malloc
-#define malloc hybrid_malloc
-#undef realloc
-#define realloc hybrid_realloc
-#undef aligned_alloc
-#define aligned_alloc hybrid_aligned_alloc
-#undef calloc
-#define calloc hybrid_calloc
-#undef free
-#define free hybrid_free
-
-extern void *hybrid_malloc (size_t);
-extern void *hybrid_calloc (size_t, size_t);
-extern void hybrid_free (void *);
-extern void *hybrid_aligned_alloc (size_t, size_t);
-extern void *hybrid_realloc (void *, size_t);
-#endif	/* emacs */
-#endif	/* HYBRID_MALLOC */
-
 /* We have to go this route, rather than the old hpux9 approach of
    renaming the functions via macros.  The system's stdlib.h has fully
    prototyped declarations, which yields a conflicting definition of
diff --git a/src/gmalloc.c b/src/gmalloc.c
index 1faf6506167..d6c5d351925 100644
--- a/src/gmalloc.c
+++ b/src/gmalloc.c
@@ -62,7 +62,7 @@ #define USE_PTHREAD
    grealloc... via the macros that follow).  The dumped emacs,
    however, will use the system malloc, realloc....  In other source
    files, malloc, realloc... are renamed hybrid_malloc,
-   hybrid_realloc... via macros in conf_post.h.  hybrid_malloc and
+   hybrid_realloc... via macros in lisp.h.  hybrid_malloc and
    friends are wrapper functions defined later in this file.  */
 #undef malloc
 #undef realloc
diff --git a/src/lisp.h b/src/lisp.h
index bf6b023fc2a..f3566ad2973 100644
--- a/src/lisp.h
+++ b/src/lisp.h
@@ -4930,10 +4930,45 @@ #define safe_calln(...) \
 
 /* Defined in unexmacosx.c.  */
 #if defined DARWIN_OS && defined HAVE_UNEXEC
+/* Redirect calls to malloc, realloc and free to a macOS zone memory allocator.
+   FIXME: Either also redirect unexec_aligned_alloc and unexec_calloc,
+   or fix this comment to explain why those two redirections are not needed.  */
 extern void unexec_init_emacs_zone (void);
 extern void *unexec_malloc (size_t);
 extern void *unexec_realloc (void *, size_t);
 extern void unexec_free (void *);
+# ifndef UNEXMACOSX_C
+#  include <stdlib.h>
+#  undef malloc
+#  undef realloc
+#  undef free
+#  define malloc unexec_malloc
+#  define realloc unexec_realloc
+#  define free unexec_free
+# endif
+#endif
+
+/* Defined in gmalloc.c.  */
+#ifdef HYBRID_MALLOC
+/* Redirect calls to malloc and friends to a hybrid allocator that
+   uses gmalloc before dumping and the system malloc after dumping.
+   This can be useful on Cygwin, for example.  */
+extern void *hybrid_aligned_alloc (size_t, size_t);
+extern void *hybrid_calloc (size_t, size_t);
+extern void *hybrid_malloc (size_t);
+extern void *hybrid_realloc (void *, size_t);
+extern void hybrid_free (void *);
+# include <stdlib.h>
+# undef aligned_alloc
+# undef calloc
+# undef malloc
+# undef realloc
+# undef free
+# define aligned_alloc hybrid_aligned_alloc
+# define calloc hybrid_calloc
+# define malloc hybrid_malloc
+# define realloc hybrid_realloc
+# define free hybrid_free
 #endif
 
 /* The definition of Lisp_Module_Function depends on emacs-module.h,
diff --git a/src/unexmacosx.c b/src/unexmacosx.c
index 7b2326441b4..d6c7686607f 100644
--- a/src/unexmacosx.c
+++ b/src/unexmacosx.c
@@ -87,15 +87,10 @@
 
 #include <config.h>
 
-/* Although <config.h> redefines malloc to unexec_malloc, etc., this
-   file wants stdlib.h to declare the originals.  */
-#undef malloc
-#undef realloc
-#undef free
-
 #include <stdlib.h>
 
 #include "unexec.h"
+#define UNEXMACOSX_C /* Tell lisp.h we want the system malloc, etc.  */
 #include "lisp.h"
 #include "sysstdio.h"
 
-- 
2.45.2

Re: Warning in lib/stdlib.c

[Stefan Kangas]

Paul Eggert <eggert@cs.ucla.edu> writes:

> In <https://bugs.gnu.org/52455#21> I just now proposed removing
> no-longer-working code that attempts to support unexec on macOS.

Yes, the unexec build on macOS is broken and won't build.  I tried
building it earlier this month with the same result as you.

We have proposed deleting the unexec build for all platforms, not just
macOS.  The plan is to merge that on February 1, 2025.

Please see:

    https://lists.gnu.org/r/emacs-devel/2024-12/msg00687.html

>  That would have simplified the attached patches.

If there are relevant simplifications that remain doing on the
scratch/no-purespace branch, feel free to install them there.