Ensure variadic call is null-terminated

[kleisauke]

Noticed on https://qa.debian.org/excuses.php?package=vips.

[kleisauke]

I'm not sure who maintains ruby-vips in Debian, it's still on v2.1.4.

@gcsideal FYI: backporting this PR should help migrate libvips to 8.16.0 in Debian.

[jcupitt]

Ooop, bad oversight. Well done for finding this!

[gcsideal]

I'm not sure who maintains ruby-vips in Debian, it's still on v2.1.4.

The tracker page of ruby-vips contain the information: Jongmin Kim and Utkarsh Gupta.
No, libvips 8.6.0 will not migrate even with this fix. It has a build time testing regression on s390x, sparc64 and hppa at least. It seems the 'testing sample.jpg pfm ... save / load difference' is too big. Need further checking.

[kleisauke]

Thanks for the information! PR libvips/libvips#4242 should fix these test failures on big-endian systems.

[gcsideal]

Thanks for the information! PR libvips/libvips#4242 should fix these test failures on little-endian systems.

Can be, but unfortunately the mentioned architectures are big-endian ones. Do you have a fix for these as well?

[kleisauke]

Apologies, I meant big-endian machines. I was confused due to the changelog note added in commit libvips/libvips@f06db0f.

[kleisauke]

ChangeLog note will be fixed via PR libvips/libvips#4246.