Compiling C source files with Clang instead of gcc when building with Haskell stack?

Currently if I build a haskell project that also has c source files, stack compiles the c source files using gcc. However, i would like to compile these C source files with Clang instead. Is it possible to change the package.yaml or stack.yaml to achieve this?

It looks like specifying something like the following in your stack.yaml file:

with-gcc: /usr/bin/clang-15

and -- if you get an error about an .addrsig opcode -- possibly adding a C flag to your .cabal file:

library ...
  ...
  cc-options: -fno-addrsig
  ...

might be sufficient. At least, I was able to get the following toy example working with clang-15.

I created a Stack project with the following files:

# stack.yaml
resolver: lts-21.0
packages:
- .
with-gcc: /usr/bin/clang-15

# clangtest.cabal
cabal-version: 1.12
name:           clangtest
version:        0.1.0.0
build-type:     Simple

executable clangtest-exe
  main-is: Main.hs
  c-sources: test.c
  cc-options: -fno-addrsig
  build-depends: base >=4.7 && <5
  default-language: Haskell2010

/* test.h */
char* world(int key);

/* test.c */
#include "test.h"

char* world(int key)
{
        switch(key) {
        case 1: return "world";
        case 2: return "Bob";
        default: return "<unknown>";
        }
}

-- Main.hs
module Main (main) where

import Foreign.C

foreign import ccall "world" world :: Int -> CString

main :: IO ()
main = do
  thing <- peekCString (world 1)
  putStrLn $ "Hello, " ++ thing

Then, I ran stack build:

$ stack build
Building all executables for `clangtest' once. After a successful build of all of them, only specified executables will be rebuilt.
clangtest> configure (exe)
Configuring clangtest-0.1.0.0...
clangtest> build (exe)
Preprocessing executable 'clangtest-exe' for clangtest-0.1.0.0..
Building executable 'clangtest-exe' for clangtest-0.1.0.0..
[1 of 1] Compiling Main
[2 of 2] Linking .stack-work/dist/x86_64-linux/Cabal-3.8.1.0/build/clangtest-exe/clangtest-exe
clangtest> copy/register
Installing executable clangtest-exe in /u/buhr/src/overflow/clangtest/.stack-work/install/x86_64-linux/af84b282df7268d5dbef65c10bee4a1a2517fa1d96db69f048f962dabf7b870f/9.4.5/bin

I verified that the C file had actually been compiled with clang:

$ strings .stack-work/dist/x86_64-linux/Cabal-3.8.1.0/build/clangtest-exe/clangtest-exe-tmp/test.o | egrep clang
Debian clang version 15.0.6

and I verified that the program actually ran:

buhr@delores:~/src/overflow/clangtest$ stack exec clangtest-exe
Hello, world