Merge pull request #766 from mokshasoft/gambit-cg

Gambit cg

docs/source/backends/gambit.rst

@@ -66,3 +66,23 @@ Gambit Directives
   .. code-block::
 
     $ idris2 --codegen chez --directive extraRuntime=/path/to/extensions.scm -o main Main.idr
+
+* ``--directive C``
+
+  Compile to C.
+
+Gambit Environment Configurations
+=================================
+
+* ``GAMBIT_GSC_BACKEND``
+
+  The ``GAMBIT_GSC_BACKEND`` variable controls which C compiler Gambit will use during compilation. E.g. to use clang:
+
+  ::
+
+    $ export GAMBIT_GSC_BACKEND=clang
+
+  Gambit after version v4.9.3 supports the ``-cc`` option, which configures
+  the compiler backend Gambit will use to build the binary. Currently to
+  get this functionality Gambit needs to be built from source, since it is
+  not yet available in a released version.

src/Compiler/Scheme/Gambit.idr

@@ -38,6 +38,13 @@ findGSC =
   do env <- getEnv "GAMBIT_GSC"
      pure $ fromMaybe "/usr/bin/env gsc" env
 
+findGSCBackend : IO String
+findGSCBackend =
+  do env <- getEnv "GAMBIT_GSC_BACKEND"
+     pure $ case env of
+              Nothing => ""
+              Just e => " -cc " ++ e
+
 schHeader : String
 schHeader = "; @generated\n
          (declare (block)
@@ -387,9 +394,15 @@ compileExpr c tmpDir outputDir tm outfile
          libsname <- compileToSCM c tm srcPath
          libsfile <- traverse findLibraryFile $ map (<.> "a") (nub libsname)
          gsc <- coreLift findGSC
-         let cmd = gsc ++
-                   " -exe -cc-options \"-Wno-implicit-function-declaration\" -ld-options \"" ++
-                   (showSep " " libsfile) ++ "\" -o \"" ++ execPath ++ "\" \"" ++ srcPath ++ "\""
+         gscBackend <- coreLift findGSCBackend
+         ds <- getDirectives Gambit
+         let gscCompileOpts =
+             case find (== "C") ds of
+                 Nothing => gscBackend ++ " -exe -cc-options \"-Wno-implicit-function-declaration\" -ld-options \"" ++
+                   (showSep " " libsfile) ++ "\""
+                 Just _ => " -c"
+         let cmd =
+             gsc ++ gscCompileOpts ++ " -o \"" ++ execPath ++ "\" \"" ++ srcPath ++ "\""
          ok <- coreLift $ system cmd
          if ok == 0
             then pure (Just execPath)