buildCross.nix-expr-c.x86_64-unknown-freebsd.x86_64-linux fails to compile

[edolstra]

Describe the bug

https://hydra.nixos.org/build/277988251

It fails with

x86_64-unknown-freebsd-ld: error: undefined symbol: operator new(unsigned long, std::align_val_t)

due to

        void * p = ::operator new(
            sizeof(EvalState),
            static_cast<std::align_val_t>(alignof(EvalState)));

in src/libexpr-c/nix_api_expr.cc.

@Ericson2314 Do we actually need the explicit alignment?

Steps To Reproduce

1. Go to '...'
2. Click on '....'
3. Scroll down to '....'
4. See error

Expected behavior

A clear and concise description of what you expected to happen.

nix-env --version output

Additional context

Add any other context about the problem here.

Priorities

Add 👍 to issues you find important.

[Ericson2314]

CC @rhelmot @artemist do you know with the variosu C++ ABI changes whether this will start working in 24.11?

@edolstra I doubt the alignment is actually funky, but I also don't know whether it is for sure. We could do a static_assert or C-style allocation (with alignment) instead, but I am hoping that the problem will also just go away.

[artemist]

Interesting... I've had issues with -Wl,-z,defs flags in lix that I fixed, but only for libc symbols, not for C++ symbols. The lix build issues were all fixed in 24.11, but IIRC C++ wasn't part of that, just Rust.

[rhelmot]

I'm not actually sure how to reproduce this - when I try to nix build github:nixos/nixpkgs/nixos-24.05#pkgsCross.x86_64-freebsd.stdenv.cc as indicated by the flake I get a gcc internal compiler error: Segmentation fault while compiling llvm17?

[rhelmot]

I ran across an old conversation (september) between myself and Joerg about this error specifically. It looks like we determined that it was already fixed by simply switching to nixpkgs-unstable, and at the time I identified NixOS/nixpkgs#316249 as the fix.