[llvm-dev] Possible UB in reading coverage mapping with compressed function names

[Igor Kudrin via llvm-dev]

Hi David, Vedant,

It looks like we might have UB somewhere connected with reading coverage 
mapping serialized in v2 format (with compressed function names).

I committed my patch, r266436, using the current format for .covmapping 
file, and then buildbots complained about it:
* 
http://lab.llvm.org:8011/builders/sanitizer-x86_64-linux-fast/builds/11935/steps/check-llvm%20ubsan/logs/stdio
* 
http://lab.llvm.org:8011/builders/sanitizer-x86_64-linux-bootstrap/builds/11460/steps/check-llvm%20ubsan/logs/stdio

I tried to reproduce the issue locally, but didn't succeed. Anyway, I've 
reapplied my patch (r266620) using the old format
for .covmapping, and buildbots are happy now.

Could you take a look on that? Do you have any idea what might cause the 
problem?

Best regards,
Igor Kudrin