libpng: fix build on FreeBSD

[rhelmot]

Description of changes

As per comment.

Things done

• Built on platform(s)
  • x86_64-linux
  • aarch64-linux
  • x86_64-darwin
  • aarch64-darwin
  • x86_64-freebsd
• For non-Linux: Is sandboxing enabled in nix.conf? (See Nix manual)
  • sandbox = relaxed
  • sandbox = true
• Tested, as applicable:
  • NixOS test(s) (look inside nixos/tests)
  • and/or package tests
  • or, for functions and "core" functionality, tests in lib/tests or pkgs/test
  • made sure NixOS tests are linked to the relevant packages
• Tested compilation of all packages that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review rev HEAD". Note: all changes have to be committed, also see nixpkgs-review usage
• Tested basic functionality of all binary files (usually in ./result/bin/)
• 24.11 Release Notes (or backporting 23.11 and 24.05 Release notes)
  • (Package updates) Added a release notes entry if the change is major or breaking
  • (Module updates) Added a release notes entry if the change is significant
  • (Module addition) Added a release notes entry if adding a new NixOS module
• Fits CONTRIBUTING.md.

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[Ericson2314]

https://sourceforge.net/p/png-mng/mailman/message/36390652/ did you try this?

[rhelmot]

That patch is already applied to libpng upstream. It doesn't help...

[paparodeo]

no rebuilds for nix-build -A libpng and nix-build -A pkgsCross.x86_64-freebsd.libpng builds successfully.

[vcunat]

Honestly I'd rather see you adding lines like

int feenableexcept(int excepts);

into one of the headers. I think this particular function should be OK without a declaration visible at call site, but this flag is global and can lead to subtle runtime breakages, e.g. see https://stackoverflow.com/a/437763/587396

[rhelmot]

I've pushed the @paparodeo patch which does basically what you've asked :)

[vcunat]

Ah, OK. I haven't read it previously, as it was a "resolved" thread.

[paparodeo]

looks good with latest patch. no rebuilds for nix-build -A libpng and nix-build -A pkgsCross.x86_64-freebsd.libpng builds successfully.

[vcunat]

Yes, I like this. Especially as the issue only happens in a test.

[github-actions]

Successfully created backport PR for release-24.05:

• [Backport release-24.05] libpng: fix build on FreeBSD #320486