use MALLOC_PERTURB_ ... or lose

[Jim Meyering]

Michal Schmidt wrote:
> On Wed, 05 May 2010 17:30:29 +0200 Jim Meyering wrote:
>> I propose (seriously, now) to add this to /etc/profile,
>> or to some always-sourced file like /etc/profile.d/glibc.sh:
>>
>>     # Enable glibc's malloc perturbing feature in Rawhide.
>>     # http://udrepper.livejournal.com/11429.html
>>     read _f _r _n _code_name < /etc/redhat-release &&
>>     case $_code_name in
>>         *Rawhide*) export MALLOC_PERTURB_=$((RANDOM % 255 + 1)) ;;
>>     esac
>
> Would export MALLOC_CHECK_=3 be a useful addition too?

Does that impose much of a performance impact?
I haven't used it or measured it enough to know off hand.

Even using MALLOC_PERTURB_=... imposes *some* cost, both in
space and in time.  I confess that I haven't measured it, either.
Rawhide already has (had?) a reputation for being slightly slower due to
added instrumentation e.g., in the kernel, so there is precedent.