GitLab

Motivation

Given this code

{-# LANGUAGE ForeignFunctionInterface, CPP #-}
{-# LANGUAGE BangPatterns #-}

module Main where

import Data.Bits (setBit)
import Data.Word (Word32)
import Data.Int (Int64)

main :: IO ()
main = offending 100 0 1

offending :: Int64 -> Int64 -> Word32 -> IO ()
offending h i id = do
    oldMask <- sendMessage h (2245) 0
    let newMask = setBit oldMask (fromIntegral id)
    sendMessage h (2244) newMask
    return ()

foreign import ccall "func" sendMessage :: Int64 -> Word32 -> Int64 -> IO Int64


--------------------------------
// C Code

#include <stdio.h>
#include <stdint.h>

int64_t func(int64_t a, int64_t d) {
    printf("ffi call");
    if (a == 1) {
        printf(" with corrupted convention\n");
    }
    else {
        printf("\n");
    }
    return 0;
}

The FFI calls show up as something like this:

  case {__pkg_ccall_GC main Int#
                     -> Word#
                     -> Int#
                     -> State# RealWorld
                     -> (# State# RealWorld, Int# #)}_d14o
                     ww_s2eI 2244## ds1_d14l ds_d14m
              of
              { (# ds2_X15i, ds3_X16f #) ->
              src<Main.hs:18:5-13>
              (# ds2_X15i, src<Main.hs:18:12-13> GHC.Tuple.() #)
              }

But it would really help readability and grepability of these things if they contained the name of the function we are calling.

Proposal