nix-shell environment does not work well with clangd

[thongpv87]

I have a cmake project with following nix environment:

with (import <nixpkgs> {});
clangStdenv.mkDerivation {
  name = "myapp";
  version = "dev-0.1";
  src = ./.;
  nativeBuildInputs = [ cmake git pkgconfig clang_9 ];
  buildInputs = [
    libpcap
    gtest
    boost169
    tbb
    protobuf
    cppzmq
    czmq
  ];
}

The app is built successfully, but clangd can not find the symbol. I thing the problem is CPATH or C_INCLUDE_PATH, CPLUS_INCLUDE_PATH is not set (https://clang.llvm.org/docs/CommandGuide/clang.html).

My temporary solution is:

$ nix-shell
$ touch main.cpp && clang++ -c main.cpp -v
 ........................
#include "..." search starts here:
#include <...> search starts here:
 /nix/store/r60zj33ql368zhlmbmkb09708cx2x62s-compiler-rt-9.0.0-dev/include
 /nix/store/95gcjjxrafz14lcm1qlr0c22cllq0z0g-compiler-rt-7.1.0-dev/include
 /nix/store/dwg4f08dfjh1bp01dl9lab37k4izl3zf-libpcap-1.9.1/include
 /nix/store/3vqq9cycszr92rra71n66hhp7nd1q3yq-gtest-1.10.0-dev/include
 /nix/store/3dzmwvwwmg9l2qhz797fwpvzq5qy8n98-boost-1.69.0-dev/include
 /nix/store/wm1nb0fi7f8zskaa9hmp318hvsqh5brj-tbb-2019_U9/include
 /nix/store/z7b936n47c6sfpjim4fkahgh5q8vwplm-protobuf-3.7.1/include
 /nix/store/8kzhxcvpp55ci4k5gv2b9gssqw6y73n4-cppzmq-4.4.1/include
 /nix/store/rfxwlichcbakhhz17vb8vjlqk5p2gkrw-czmq-4.2.0/include
 /nix/store/z3ly1ixkz3zk6nmhwyrirjq7y5mb5gmy-zeromq-4.3.2/include
 /nix/store/vgn1sxcj5ma9m5bhjps1q9jx3q2ab27c-gcc-8.3.0/include/c++/8.3.0
 /nix/store/vgn1sxcj5ma9m5bhjps1q9jx3q2ab27c-gcc-8.3.0/include/c++/8.3.0/x86_64-unknown-linux-gnu
 /nix/store/86s2mcrbl9i020zdxyv84s8vc49hiwis-clang-wrapper-9.0.0/resource-root/include
 /nix/store/zknwniygdjjhizjw70jdk67fyf4y2bn9-glibc-2.27-dev/include

$ # set the CPATH variable according to include path in * #include<...> starts here * 
$ export CPATH=......
$ clangd&

I thing this should be added to the mkDerivation function

[lheckemann]

Does this work if you make the set recursive (add rec between mkDerivation and {) and add

CPATH = lib.makeSearchPathOutput "dev" "include" buildInputs;

to the set?

[LnL7]

Unlike clang/clang++ the clangd binary isn't wrapped to make it resolve nix inputs. I currently use compile_fags.txt to make multiple tools aware of them. We might be able to wrap clangd, but that's an issue that belongs in nixpkgs.

[thongpv87]

@lheckemann It works perfectly. Thank you so much.

[lheckemann]

Someone please close this, since it's not a nix issue

[lheckemann]

Related nixpkgs issue: NixOS/nixpkgs#92739