Re: JIT breaks PostGIS

Hi,

On 2018-07-21 23:14:47 +0300, Darafei "Komяpa" Praliaskouski wrote:
> Today I spent some time closing PostGIS tickets in preparation to Monday's
> release.
> 
> One of the blockers, https://trac.osgeo.org/postgis/ticket/4125, was filed
> by Postgres APT repository maintainer Christoph Berg who noticed a test
> suite failure on Debian Stretch with Postgres 11.
> 
> Upon investigation we found:
>  - A build for Ubuntu Bionic installed on Debian Stretch passes the suite,
> requiring llvm6;
>  - A build for Debian Stretch fails the suite on a call to external library
> GEOS, showing no traces of JIT in the stacktrace;
>  - Setting jit=off lets the suite pass;
>  - The query called in clean session by itself does not crash Postgres.
> Queries above it are required to reproduce the crash;
>  - The crash affects not only Stretch, but customly collected Postgres 11 /
> clang 3.9 on Travis CI running Ubuntu Trusty:
> https://github.com/postgis/postgis/pull/262.
> 
> I suspect that a fix would require to bisect llvm/clang version which stops
> showing this behavior and making it a new minimum for JIT, if this is not a
> symptom of bigger (memory management?) problem.

Could you attempt to come up with a smaller reproducer?

Greetings,

Andres Freund