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Postings from June 2022
I've been trying to track down a tricky memory-leak bug, so I thought
I'd have a go at using the PERL_MEM_LOG machinery.
Turns out: it's broken and doesn't work; and even if it were to work it
would be borderline-useless.
* Broken: Attempting to actually use it causes a snprintf buffer
overflow:
$ PERL_MEM_LOG=s bleadperl program-under-test.pl
...
panic: snprintf buffer overflow at /home/leo/perl5/perlbrew/perls/bleadperl/lib/5.37.1/XSLoader.pm line 112.
Compilation failed in require.
BEGIN failed--compilation aborted.
* Useless: Before it failed, it did print lots of SV creation logs;
almost every one of them giving the caller location as
Perl_newSV_type at sv_inline.h line 369 (apart from a scattered few
that show Perl_sv_newmortal()).
So even if I fix the snprintf bug, I'll still end up with a log that
doesn't contain useful information.
This all sounds somewhat familiar to me - turns out I ran into this
second part 3 years ago and came up with a solution. I posted a patch
at the time that didn't end up going anywhere:
https://www.nntp.perl.org/group/perl.perl5.porters/2019/01/msg253378.html
I'll have a go at resurrecting that patch and making it work on current
blead; if I can make it work expect a PR to add it here.
--
Paul "LeoNerd" Evans
leonerd@leonerd.org.uk | https://metacpan.org/author/PEVANS
http://www.leonerd.org.uk/ | https://www.tindie.com/stores/leonerd/
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