GNU bug report logs - #6170
24.0.50; Compiling on solaris2.10 with gcc doesn't define alloca

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From: help-debbugs <at> gnu.org (GNU bug Tracking System)
To: Lawrence Mitchell <wence <at> gmx.li>
Subject: bug#6170: closed (Re: bug#6170: 24.0.50; Compiling on solaris2.10
 with gcc doesn't define alloca)
Date: Wed, 02 Jun 2010 09:25:02 +0000

[Message part 1 (text/plain, inline)]

Your bug report

#6170: 24.0.50; Compiling on solaris2.10 with gcc doesn't define alloca

which was filed against the emacs package, has been closed.

The explanation is attached below, along with your original report.
If you require more details, please reply to 6170 <at> debbugs.gnu.org.

-- 
6170: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=6170
GNU Bug Tracking System
Contact help-debbugs <at> gnu.org with problems

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From: Dan Nicolaescu <dann <at> gnu.org>
To: Lawrence Mitchell <wence <at> gmx.li>
Cc: 6170-done <at> debbugs.gnu.org
Subject: Re: bug#6170: 24.0.50;
	Compiling on solaris2.10 with gcc doesn't define alloca
Date: Wed, 02 Jun 2010 05:24:36 -0400

Lawrence Mitchell <wence <at> gmx.li> writes:

> Dan Nicolaescu wrote:
>> Lawrence Mitchell <wence <at> gmx.li> writes:
>
>>> On this system, <stdlib.h> is provided by Sun and therefore
>>> doesn't define alloca, unlike on a typical GNU/linux system where
>>> <stdlib.h> contains the following:
>
>>> | #if defined __USE_GNU || defined __USE_BSD || defined __USE_MISC
>>> | # include <alloca.h>
>>> | #endif /* Use GNU, BSD, or misc.  */
>
>>> When compiling emacs with gcc, alloca is therefore undefined.
>>> The culprit is this snippet in configure.in:
>
>>> | #ifndef __GNUC__
>>> | # ifdef HAVE_ALLOCA_H
>>> | #  include <alloca.h>
>>> | # else /* AIX files deal with #pragma.  */
>>> | #  ifndef alloca /* predefined by HP cc +Olibcalls */
>>> | char *alloca ();
>>> | #  endif
>>> | # endif /* HAVE_ALLOCA_H */
>>> | #endif /* __GNUC__ */
>
>
>> "info autoconf" says that this is the proper way to do it:
>
>>           #ifdef HAVE_ALLOCA_H
>>           # include <alloca.h>
>>           #elif defined __GNUC__
>>           # define alloca __builtin_alloca
>>           #elif defined _AIX
>>           # define alloca __alloca
>>           #elif defined _MSC_VER
>>           # include <malloc.h>
>>           # define alloca _alloca
>>           #else
>>           # include <stddef.h>
>>           # ifdef  __cplusplus
>>           extern "C"
>>           # endif
>>           void *alloca (size_t);
>>           #endif
>
>> Not sure we need the last #else part, or the _MSC_VER part...
>
> Is there any movement on getting this fix, or something like it,
> installed?  It doesn't seem like a controversial change.

Should be fixed now.

[Message part 3 (message/rfc822, inline)]

From: Lawrence Mitchell <wence <at> gmx.li>
To: bug-gnu-emacs <at> gnu.org
Subject: 24.0.50; Compiling on solaris2.10 with gcc doesn't define alloca
Date: Tue, 11 May 2010 11:57:17 +0100

On this system, <stdlib.h> is provided by Sun and therefore
doesn't define alloca, unlike on a typical GNU/linux system where
<stdlib.h> contains the following:

| #if defined __USE_GNU || defined __USE_BSD || defined __USE_MISC
| # include <alloca.h>
| #endif /* Use GNU, BSD, or misc.  */

When compiling emacs with gcc, alloca is therefore undefined.
The culprit is this snippet in configure.in:

| #ifndef __GNUC__
| # ifdef HAVE_ALLOCA_H
| #  include <alloca.h>
| # else /* AIX files deal with #pragma.  */
| #  ifndef alloca /* predefined by HP cc +Olibcalls */
| char *alloca ();
| #  endif
| # endif /* HAVE_ALLOCA_H */
| #endif /* __GNUC__ */

On this system, configure correctly defines both HAVE_ALLOCA_H
and HAVE_ALLOCA, but since the inclusion is guarded by __GNUC__
not being defined, we never include <alloca.h>.

I think the correct fix is to unconditionally define alloca if
__GNUC__ is detected, see patch below.  Note that this is closer
to how autoconf checks for the presence of the alloca function.

Possible changelog entry:

2010-05-11  Lawrence Mitchell  <wence <at> gmx.li>

	* configure.in: Unconditionally define alloca if __GNUC__ is
	detected.

diff --git a/configure.in b/configure.in
index 8a7d9be..98b6abb 100644
--- a/configure.in
+++ b/configure.in
@@ -3360,6 +3360,9 @@ extern char *getenv ();
 char *alloca ();
 #  endif
 # endif /* HAVE_ALLOCA_H */
+#else
+# undef alloca
+# define alloca __builtin_alloca
 #endif /* __GNUC__ */
 #ifndef HAVE_SIZE_T
 typedef unsigned size_t;

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