gmp: fix cross compilation to windows

[alexfmpe]

Things done

• [] Tested using sandboxing (nix.useSandbox on NixOS, or option sandbox in nix.conf on non-NixOS linux)
• Built on platform(s)
  • NixOS
  • macOS
  • other Linux distributions
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• 21.11 Release Notes (or backporting 21.05 Relase 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.

[alexfmpe]

CPPFLAGS=-fstack-protector also gets through the __memset_chk error, but later hits undefined reference to `__stack_chk_fail'`

[alexfmpe]

Not sure if this should be backported to 4.3.2.nix / 5.1.x.nix

[Mindavi]

Diff LGTM

[alexfmpe]

I just ran into the same issue when trying to build pkgsCross.mingw32.hello on master. Same fix. Maybe this should go somewhere more general?
This seems to be a somewhat recent issue, I do not run into it on nixpkgs-20.09.
cc @Ericson2314

[alyssais]

This one also needs to target staging, due to the number of rebuilds.

[alexfmpe]

This one also needs to target staging, due to the number of rebuilds.

Actually, I'm confused.
I see @NixOS/ofborg tagged this as linux/darwin rebuilds, but I'd expect lib.optionalString stdenv.targetPlatform.isWindows to prevent those from being affected? And AFAICT the mingw build was broken, so maybe no actual rebuild is triggered?

[FRidh]

I see @NixOS/ofborg tagged this as linux/darwin rebuilds, but I'd expect lib.optionalString stdenv.targetPlatform.isWindows to prevent those from being affected? And AFAICT the mingw build was broken, so maybe no actual rebuild is triggered?

That's because optionalString still needs to return something, so NIX_LDFLAGS is still set. Don't worry about it.

[symphorien]

I just ran into the same issue when trying to build pkgsCross.mingw32.hello on master. Same fix. Maybe this should go somewhere more general?

adding -lssp could probably go in pkgs/build-support/cc-wrapper/add-hardening.sh maybe?

[alexfmpe]

Turns out this isn't quite right.
While it fixes the build issue, and makes pkgsCross.mingwW64.hello run fine (via wine) on top of master, that's not the case for staging - there it still builds but we get a runtime crash from not finding dlls.

adding -lssp could probably go in pkgs/build-support/cc-wrapper/add-hardening.sh maybe?

This ended up breaking other things, including a dependency of gmp: mcfgthreads-x86_64-w64-mingw32-git, because it can't find libssp

configure:2726: $? = 1
configure:2746: checking whether the C compiler works
configure:2768: x86_64-w64-mingw32-gcc    conftest.c  >&5
/nix/store/d8j3pwvdgqpm06qsg37d0w8j0w8vcsza-x86_64-w64-mingw32-binutils-2.35.1/bin/x86_64-w64-mingw32-ld: cannot find -lssp
collect2: error: ld returned 1 exit status

It seems actually fixing this requires #38632, which in turn requires #132340, so I'm marking this as a draft for the time being.

[alexfmpe]

It seems actually fixing this requires #38632, which in turn requires #132340, so I'm marking this as a draft for the time being.

pkgsCross.mingwW64.gmp builds again on staging (likely since #133479).
I don't think this PR per-se is useful anymore, as the next improvement will come from the above linked PRs.