A transitive dep (a C++ lib) compiled with wrong flags, how can be overridden

kindoblue · February 8, 2023, 10:29am

Sorry, I am a newby with nix (using the package manager under darwin) and the forum.

I am trying to create a flake.nix for a c++ project. The main goal is to use a nix develop shell for development. This is how I instatiate the shell within the flake

    devShells.default = pkgs.mkShell.override { stdenv = pkgs.gcc12Stdenv; } rec {
      name = "my-c++-project";

      packages = with pkgs; [
        cmake
        ninja

        gtest

        spdlog
        abseil-cpp
      ];

  });

As you can see, I am trying to use gcc-12 (on darwin).
The problem is that spdlog brings in a fmt library which at link time gives this error:

Undefined symbols for architecture arm64:
  "__ZN3fmt2v87vformatB5cxx11ENS0_17basic_string_viewIcEENS0_17basic_format_argsINS0_20basic_format_contextINS0_8appenderEcEEEE",

which is the same to say that the following is missing:

fmt::v8::vformat[abi:cxx11](fmt::v8::basic_string_view<char>, fmt::v8::basic_format_args<fmt::v8::basic_format_context<fmt::v8::appender, char> >)

So probably, the fmt lib was compiled with the wrong C++ ABI, and the question finally is: how can override the way fmt is being compiled?

wamserma · February 8, 2023, 8:23pm

In your case the stdenv change doesn’t trickle down into your used pkgs,
see also here:
https://groups.google.com/g/nix-devel/c/T8YlEcJj1G0
ans here:

github.com/NixOS/nixpkgs

How to override the default compiler

opened 03:23PM - 07 Apr 18 UTC

veprbl

0.kind: question

I'm looking to compile some packages using gcc 4.8. My original thought was to o…nly override ```stdenv``` for C++ packages (I assumed that only C++ ABI will be incompatible between gcc7 and gcc4.8). This worked well until I've tried to build boost: ```nix { nixpkgs ? import <nixpkgs> {} }: let stdenv = nixpkgs.overrideCC nixpkgs.stdenv nixpkgs.gcc48; in { boost = nixpkgs.boost.override { inherit stdenv; }; } ``` This clearly builds ```gcc-gnu-7.3.0``` configuration that is incompatible with the rest of my packages. This seems to be due to boost using ```buildPackages.stdenv.cc``` in ```nativeBuildInputs```, which I don't quite understand. I've decided that I might need to do a global override (actually I would prefer it that way). My first thought was to use overlays: ```nix { nixpkgs ? import <nixpkgs> {} }: let overlay = self: super: { stdenv = super.overrideCC nixpkgs.stdenv nixpkgs.gcc48; }; in import <nixpkgs> { overlays = [ overlay ]; } ``` This is ugly, but it fixes boost. Unfortunately this breaks ```pam```: ``` libtool: link: gcc -g -O2 -W -Wall -Wbad-function-cast -Wcast-align -Wcast-qual -Wmissing-declarations -Wmissing-prototypes -Wpointer-arith -Wreturn-type -Wstrict-prototypes -Wwrite-strings -Winline -Wshadow -Wl,--as-needed -Wl,--no-undefined -Wl,-O1 -o padout parse_l.o parse_y.o parse_y.o: In function `memset': /nix/store/cbr1j6vv0zss8x4dkv9i2rqqlwkc8fp9-glibc-2.26-131-dev/include/bits/string_fortified.h:67: undefined reference to `__warn_memset_zero_len' collect2: error: ld returned 1 exit status ``` This is seems to be due to glibc being compiled with bootstrap-gcc which is version 7.3. I haven't figured out how to overcome this. Does anybody have suggestions how I can compile packages with a different compiler?

kindoblue · February 9, 2023, 6:01pm

Indeed if I do the following

nix-repl> :b fmt_8.override { stdenv = gcc12Stdenv; }

This derivation produced the following outputs:
  dev -> /nix/store/lf28igdjc230mrgs1d000qy5cfcyjlf1-fmt-8.1.1-dev
  out -> /nix/store/y85s6w89vcs08k1n4gqrr4dnnvqqv01q-fmt-8.1.1

And if you check the corresponding library, you can see the correct symbol exported

/nix/store/y85s6w89vcs08k1n4gqrr4dnnvqqv01q-fmt-8.1.1/lib ⌚ 18:49:55
$ nm --demangle --defined-only  libfmt.8.1.1.dylib | grep abi
00000000000175e0 T fmt::v8::vformat[abi:cxx11](fmt::v8::basic_string_view<char>, fmt::v8::basic_format_args<fmt::v8::basic_format_context<fmt::v8::appender, char> >)

I am still struggling to write a decent override in the flake.nix without getting strange errors, but at least I have a clue now. Thanks