Segmentation fault/GC assertion failure (Rakudo Perl 6) #801

hoelzro opened this Issue Jul 29, 2012 · 3 comments

4 participants


Hi everyone,

I found an issue while working on an application in Perl 6, and I've concluded that the issue lies within the Parrot runtime. First of all, here's a link to the corresponding issue in the Rakudo bug tracker:

I'm confident that the issue is Parrot-related because it goes away when I build Parrot with --optimize. I've tried this with both Parrot 4.6.0 and Parrot HEAD (11f9d7c), and I encounter the error both times.



This issue looks to me like a case where a PMC is not being properly marked. When the PMC is used later it's considered dead (on the free list), but somebody is still holding a reference to it.

When you use --optimize, the assertion disappears and the inconsistent data should indeed cause a segfault.

Tracing down these kinds of issues is notoriously difficult. Because of the nature of this bug, I suspect that the root cause of it might be in the nativecall implementation or in the code that's being called, keeping a PMC reference but not properly marking that PMC for GC. I'll do what I can to look at this issue tonight or sometime this week.


The example code linked in the RT ( is no longer available. Please make this available again or better yet, provide a Gist.

Parrot Virtual Machine member

This is most likely fixed with the Coroutine.mark update with 6.9.0

@rurban rurban closed this Nov 23, 2014
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