Re: please set both MALLOC_PERTURB_ and MALLOC_CHECK_ envvars

[Jim Meyering <jim@meyering.net>]

Paul Eggert wrote:

> On 05/27/11 14:50, Jim Meyering wrote:
>>     export MALLOC_PERTURB_=$((RANDOM % 255 + 1))
>>     export MALLOC_CHECK_=3
>>
>
> I tried that, on Fedora 14 x86-64, and the Emacs trunk build failed
> as follows:
>
>   Compiling language/thai-word.el
>
>   In toplevel form:
>   language/thai-word.el:10738:5:Error: Memory exhausted--use C-x s
> then exit and restart Emacs
>   make[2]: *** [language/thai-word.elc] Error 1
>   make[2]: Leaving directory `/home/eggert/src/gnu/emacs/int-hash/lisp'
>
> As near as I can discover, Emacs was fine, but the malloc debugging
> caused it to use so much more memory that Emacs ran out of memory
> trying to compile thai-word.el.  This is on a host with
> 8 GiB of RAM.
>
> Perhaps there is a real Emacs bug in there somewhere, but I spent
> a reasonable amount of time looking for it unsuccessfully.

Same here.  I even bisected back through several years of commits to
find the one that *appeared* to introduce this problem:
    http://thread.gmane.org/gmane.emacs.devel/137942
But all that was assuming a reliable compiler.

With those envvar settings, I've been bootstrapping emacs for
months, but only with this kludge:

     make bootstrap RUN_TEMACS='MALLOC_CHECK_=0 ./temacs'

Yesterday, I found that I can bootstrap with no kludge at all as long
as I use the latest gcc-4.7.0.  I.e., with that compiler, a plain
"make bootstrap" now succeeds in spite of my aggressive envvar settings.