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haskell - 使用 nix-shell 查找带有 cabal 的外国图书馆

问题描述

我有一个类似的问题：Cabal can't find foreign library when building on NixOS

基本上我cabal2nix用来从包含以下内容的 package.yaml 生成：

extra-libraries:
  - libmnl

这会产生一个 cabal.nix 文件：

{ mkDerivation, base, bytestring, cereal, containers, hpack
, iproute, lens, libmnl, netlink, primitive
, resourcet, safe-exceptions, stdenv, transformers
}:
mkDerivation {
  pname = "relay";
  version = "0.1.0.0";
  src = ./.;
  libraryHaskellDepends = [
    base bytestring cereal containers iproute lens netlink
    primitive resourcet safe-exceptions transformers
  ];
  librarySystemDepends = [ libmnl ];
  libraryToolDepends = [ hpack ];
  testHaskellDepends = [
    base bytestring cereal containers iproute lens netlink
    primitive resourcet safe-exceptions transformers
  ];
  testSystemDepends = [ libmnl ];
  preConfigure = "hpack";
  homepage = "https://github.com/MatrixAI/Relay#readme";
  license = stdenv.lib.licenses.asl20;
}

如果我通过 进入这个nix-shell，然后运行cabal configure​​. 它抱怨它找不到 libmnl：

Resolving dependencies...
Configuring relay-0.1.0.0...
cabal: Missing dependency on a foreign library:
* Missing (or bad) C library: libmnl
This problem can usually be solved by installing the system package that
provides this library (you may need the "-dev" version). If the library is
already installed but in a non-standard location then you can use the flags
--extra-include-dirs= and --extra-lib-dirs= to specify where it is.If the
library file does exist, it may contain errors that are caught by the C
compiler at the preprocessing stage. In this case you can re-run configure
with the verbosity flag -v3 to see the error messages.

也在gcc -c test.c -lmnl这个文件上nix-shell运行：

#include <libmnl/libmnl.h>

int main() { return 0; }

那么为什么 cabal 找不到libmnl但gcc可以在nix-shell.

使用它运行-v3时似乎尝试链接到-llibmnl. 但正确的链接应该是-lmnl. 这似乎很成问题，有没有办法告诉 cabal 与 flag 链接-lmnl，不是-llibmnl吗？

我发现，如果我编辑 Cabal 文件并将其更改extra-libraries为指向mnl而不是libmnl，那么它会通过更改 Cabal 尝试链接的方式来工作。但是，cabal2nix然后在获取时package.yaml生成libmnl哪个是 Nix 的正确包属性。看来extra-libraries应该是mnl，而cabal.nix应该是libmnl。

标签： haskellcabalnix

解决方案

基本上extra-libraries不需要mnl使用libmnl。然后在使用时cabal2nix，需要将libmnl包映射到mnl属性。这是通过上游 cabal2nix 映射 mnl 到 libmnl 提交解决的：https ://github.com/NixOS/cabal2nix/issues/413#event-2257811946

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