Bug#1115705: libsdl3-0: 3.3.x regression: SDL_image's showimage example segfaults on s390x

[Simon McVittie]

Package: libsdl3-0
Version: 3.3~git20250903.1+ds-1
Severity: serious
Tags: experimental upstream unreproducible moreinfo
Control: affects -1 + src:libsdl3-image
Forwarded: https://github.com/libsdl-org/SDL/issues/13953
X-Debbugs-Cc: debian-s390 at lists.debian.org
User: debian-s390 at lists.debian.org
Usertags: s390x
User: debian-ci at lists.debian.org
Usertags: regression

The Debian packaging for SDL_image has an automated smoke-test which 
copies out its showimage example into a temporary directory, compiles 
it, and runs it with the -save and -quit options. See 
debian/tests/libsdl3-image-dev in the libsdl3-image source package.

When using libsdl3-0 3.2.x from Debian testing/unstable, this works fine on 
all of Debian's supported architectures, including s390x. However, when 
using libsdl3-0 3.3 git snapshots from experimental, on s390x (only), the 
resulting showimage program crashes with a segfault:

 62s + xvfb-run -a -s -screen 0 1280x1024x24 -noreset ./showimage -quit -save debian-logo.bmp debian-logo.png
 62s Segmentation fault

(I can't immediately tell *what* is segfaulting, although I assume it's 
./showimage itself rather than Xvfb.)

I tried to reproduce this on the s390x porterbox but was unable to do 
so: a newly-built showimage and the precompiled copy in the 
libsdl3-image-tests package both seem to work fine. But the crash 
appears to be reliable/reproducible on the ci.debian.net autopkgtest 
runner, which I cannot access interactively.

Please could a porter try to reproduce this and get a backtrace for 
upstream to look at?

s390x mainframes are not noted for their gaming capabilities, so if this 
is not resolved by the time SDL 3.4 is stable, I'm unlikely to let this 
block upgrading SDL for all the other architectures.

Thanks,
    smcv