https://github.com/libsdl-org/autoconf/commit/5c070747d117a9a226a63dd53c1679e2a217c86d
From 5c070747d117a9a226a63dd53c1679e2a217c86d Mon Sep 17 00:00:00 2001
From: Paul Eggert <[EMAIL REDACTED]>
Date: Thu, 20 Dec 2012 21:21:04 -0800
Subject: [PATCH] AC_FUNC_ALLOCA: port to recent BSDs and remove obsolete AIX
* doc/autoconf.texi (Particular Functions): Remove the AIX case
from the recommended code, as the most recent version of the AIX
compiler that IBM still supports (V10.1 as of this writing) has
<alloca.h> and thus longer needs this, and the old suggestion
wasn't completely working anyway. Remove obsolete discussion of
SVR3 libPW alloca and of SVR4 libucb alloca.
* lib/autoconf/functions.m4 (AC_FUNC_ALLOCA):
Rework to match documentation, including abovementioned AIX change.
Inconsistency with documentation reported by Steven G. Johnson in
<http://lists.gnu.org/archive/html/autoconf/2003-03/msg00179.html>.
As this adds stdlib.h, it should also fix the problems on recent
BSD platforms noted by Patrick Welche in
http://lists.gnu.org/archive/html/autoconf-patches/2012-12/msg00009.html
though the fix differs from NetBSD's current workaround.
Also, don't bother checking for alloca if <alloca.h> works,
as the latter implies the former.
(cherry picked from commit fd29dbd7d966f0fbde031a67955d77d50268c3d5)
---
doc/autoconf.texi | 23 +++++------------------
lib/autoconf/functions.m4 | 34 +++++++++++++++++-----------------
2 files changed, 22 insertions(+), 35 deletions(-)
diff --git a/doc/autoconf.texi b/doc/autoconf.texi
index 93ab1ac4..5a101a00 100644
--- a/doc/autoconf.texi
+++ b/doc/autoconf.texi
@@ -4825,15 +4825,11 @@ in some cases how they respond when given certain arguments.
@prindex @code{alloca}
@hdrindex{alloca.h}
@c @caindex working_alloca_h
-Check how to get @code{alloca}. Tries to get a builtin version by
-checking for @file{alloca.h} or the predefined C preprocessor macros
-@code{__GNUC__} and @code{_AIX}. If this macro finds @file{alloca.h},
-it defines @code{HAVE_ALLOCA_H}.
-
-If those attempts fail, it looks for the function in the standard C
-library. If any of those methods succeed, it defines
-@code{HAVE_ALLOCA}. Otherwise, it sets the output variable
-@code{ALLOCA} to @samp{$@{LIBOBJDIR@}alloca.o} and defines
+Check for the @code{alloca} function. Define @code{HAVE_ALLOCA_H} if
+@file{alloca.h} defines a working @code{alloca}. If not, look for a
+builtin alternative. If either method succeeds, define
+@code{HAVE_ALLOCA}. Otherwise, set the output variable @code{ALLOCA} to
+@samp{$@{LIBOBJDIR@}alloca.o} and define
@code{C_ALLOCA} (so programs can periodically call @samp{alloca (0)} to
garbage collect). This variable is separate from @code{LIBOBJS} so
multiple programs can share the value of @code{ALLOCA} without needing
@@ -4841,13 +4837,6 @@ to create an actual library, in case only some of them use the code in
@code{LIBOBJS}. The @samp{$@{LIBOBJDIR@}} prefix serves the same
purpose as in @code{LIBOBJS} (@pxref{AC_LIBOBJ vs LIBOBJS}).
-This macro does not try to get @code{alloca} from the System V R3
-@file{libPW} or the System V R4 @file{libucb} because those libraries
-contain some incompatible functions that cause trouble. Some versions
-do not even contain @code{alloca} or contain a buggy version. If you
-still want to use their @code{alloca}, use @code{ar} to extract
-@file{alloca.o} from them instead of compiling @file{alloca.c}.
-
Source files that use @code{alloca} should start with a piece of code
like the following, to declare it properly.
@@ -4866,8 +4855,6 @@ like the following, to declare it properly.
#elif !defined alloca
# ifdef __GNUC__
# define alloca __builtin_alloca
-# elif defined _AIX
-# define alloca __alloca
# elif defined _MSC_VER
# include <malloc.h>
# define alloca _alloca
diff --git a/lib/autoconf/functions.m4 b/lib/autoconf/functions.m4
index 355e9e79..aff5b98e 100644
--- a/lib/autoconf/functions.m4
+++ b/lib/autoconf/functions.m4
@@ -372,36 +372,36 @@ AC_CACHE_CHECK([for working alloca.h], ac_cv_working_alloca_h,
[ac_cv_working_alloca_h=no])])
if test $ac_cv_working_alloca_h = yes; then
AC_DEFINE(HAVE_ALLOCA_H, 1,
- [Define to 1 if you have <alloca.h> and it should be used
- (not on Ultrix).])
+ [Define to 1 if <alloca.h> works.])
fi
AC_CACHE_CHECK([for alloca], ac_cv_func_alloca_works,
-[AC_LINK_IFELSE([AC_LANG_PROGRAM(
-[[#ifdef __GNUC__
-# define alloca __builtin_alloca
-#else
-# ifdef _MSC_VER
+[if test $ac_cv_working_alloca_h = yes; then
+ ac_cv_func_alloca_works=yes
+else
+ AC_LINK_IFELSE([AC_LANG_PROGRAM(
+[[#if defined STDC_HEADERS || defined HAVE_STDLIB_H
+# include <stdlib.h>
+#endif
+#include <stddef.h>
+#ifndef alloca
+# ifdef __GNUC__
+# define alloca __builtin_alloca
+# elif defined _MSC_VER
# include <malloc.h>
# define alloca _alloca
# else
-# ifdef HAVE_ALLOCA_H
-# include <alloca.h>
-# else
-# ifdef _AIX
- #pragma alloca
-# else
-# ifndef alloca /* predefined by HP cc +Olibcalls */
-void *alloca (size_t);
-# endif
-# endif
+# ifdef __cplusplus
+extern "C"
# endif
+void *alloca (size_t);
# endif
#endif
]], [[char *p = (char *) alloca (1);
if (p) return 0;]])],
[ac_cv_func_alloca_works=yes],
[ac_cv_func_alloca_works=no])])
+fi
if test $ac_cv_func_alloca_works = yes; then
AC_DEFINE(HAVE_ALLOCA, 1,