Respect ghc-options and with-gcc when compiling C sources

This fix allows users to override the C/C++ compiler, either by passing
--with-gcc to configure or adding -pgmc to ghc-options in their Cabal
file.

Tested manually with a project using C++ sources that require a more
recent version of clang than the default install (macOS). Inspected the
output of `Setup.hs build -v` to confirm that the correct arguments are
being passed to GHC when compiling the C++ sources.

Resolves: #4439

Author: syntheorem

Cabal/ChangeLog.md

@@ -215,6 +215,8 @@
     ([#5431](https://github.com/haskell/cabal/pull/5431)).
   * Pass command line arguments to `hsc2hs` using response files when possible
     ([#3122](https://github.com/haskell/cabal/issues/3122)).
+  * `ghc-options` and `--with-gcc` are now passed to GHC when compiling
+    C and C++ sources ([#4439](https://github.com/haskell/cabal/issues/4439)).
 
 ----
 

Cabal/src/Distribution/Simple/GHC/Internal.hs

@@ -301,7 +301,10 @@ componentCcGhcOptions verbosity _implInfo lbi bi clbi odir filename =
                                   NormalDebugInfo  -> ["-g"]
                                   MaximalDebugInfo -> ["-g3"]) ++
                                   ccOptions bi,
-      ghcOptObjDir         = toFlag odir
+      ghcOptCcProgram      = maybeToFlag $ programPath <$>
+                                 lookupProgram gccProgram (withPrograms lbi),
+      ghcOptObjDir         = toFlag odir,
+      ghcOptExtra          = hcOptions GHC bi
     }
 
 
@@ -337,7 +340,10 @@ componentCxxGhcOptions verbosity _implInfo lbi bi clbi odir filename =
                                   NormalDebugInfo  -> ["-g"]
                                   MaximalDebugInfo -> ["-g3"]) ++
                                   cxxOptions bi,
-      ghcOptObjDir         = toFlag odir
+      ghcOptCcProgram      = maybeToFlag $ programPath <$>
+                                 lookupProgram gccProgram (withPrograms lbi),
+      ghcOptObjDir         = toFlag odir,
+      ghcOptExtra          = hcOptions GHC bi
     }
 
 

Cabal/src/Distribution/Simple/Program/GHC.hs

@@ -446,6 +446,9 @@ data GhcOptions = GhcOptions {
   -- | Extra header files to include for old-style FFI; the @ghc -#include@ flag.
   ghcOptFfiIncludes    :: NubListR FilePath,
 
+  -- | Program to use for the C and C++ compiler; the @ghc -pgmc@ flag.
+  ghcOptCcProgram      :: Flag FilePath,
+
   ----------------------------
   -- Language and extensions
 
@@ -691,6 +694,7 @@ renderGhcOptions comp _platform@(Platform _arch os) opts
                 _ -> "-optc"
     in [ cxxflag ++ opt | opt <- ghcOptCxxOptions opts]
   , [ "-opta" ++ opt | opt <- ghcOptAsmOptions opts]
+  , concat [ ["-pgmc", cc] | cc <- flag ghcOptCcProgram ]
 
   -----------------
   -- Linker stuff