Subject: bug#24065: commit 09ece4d341a7 (Restore the calloc family) causes miscompile for gcc-5 and higher

From: Markus Trippelsdorf <[email-masked]>
Date: Mon, 25 Jul 2016 14:55:49 +0200

On 2016.07.25 at 14:38 +0200, Wolfgang Jenkner wrote:
> Markus Trippelsdorf <[email-masked]> wrote:
> 
> > commit 09ece4d341a7e07fab7be22868ebcadae8641c79
> > Author: Wolfgang Jenkner <[email-masked]>
> > Date:   Tue Feb 9 15:04:40 2016 -0800
> >
> >     Restore the calloc family.
> >
> > causes gcc-5 and higher to compile calloc to an endless loop.
> > -fno-builtin-malloc should be used to work around the problem.
> 
> This was the reason for the (compiler-independent) work-around
> discussed in
> 
> http://debbugs.gnu.org/cgi/bugreport.cgi?bug=22085
> 
> and committed in
> 
> commit 4b1436b702d56eedd27a0777fc7232cdfb7ac4f6
> Author: Wolfgang Jenkner <[email-masked]>
> Date:   Sat Dec 26 12:12:02 2015 -0800
> 
>     Always define gmalloc etc. in src/gmalloc.c
>      
> The commit you cited shouldn't change that, I think.
> 
> In any case, that work-around seems to work for DragonflyBSD, which
> has gcc 5 as base compiler, and, for the time being (i.e., emacs-25
> branch), actually uses the malloc implemented in src/gmalloc, cf.
> 
> https://github.com/DragonFlyBSD/DPorts/tree/master/editors/emacs-devel
> 
> So, it would be useful to know on which system compilation fails.

This happens on a Gentoo system (glibc trunk, gcc-6 latest branch):

(gdb) run
Starting program: /var/tmp/portage/app-editors/emacs-24.5-r3/work/emacs-24.5/src/temacs --batch --load loadup bootstrap

Program received signal SIGSEGV, Segmentation fault.
0x00000000005cac25 in calloc (nmemb=<error reading variable: DWARF-2 expression error: Loop detected (257).>, size=size@entry=1) at gmalloc.c:1529
1529      result = malloc (bytes);
(gdb) bt
#0  0x00000000005cac25 in calloc (nmemb=<error reading variable: DWARF-2 expression error: Loop detected (257).>, size=size@entry=1) at gmalloc.c:1529
#1  0x00000000005cac2a in calloc (nmemb=<error reading variable: DWARF-2 expression error: Loop detected (257).>, size=size@entry=1) at gmalloc.c:1529
#2  0x00000000005cac2a in calloc (nmemb=<error reading variable: DWARF-2 expression error: Loop detected (257).>, size=size@entry=1) at gmalloc.c:1529
...

Adding -fno-builtin-malloc to CFLAGS fixes the issue for me.

-- 
Markus