Allow compilation of C/C++/ObjC/ObjC++ files with module from TH

The main goal is to easily allow the inline-c project (and
similar projects such as inline-java) to emit C/C++ files to
be compiled and linked with the current module.

Moreover, `addCStub` is removed, since it's quite fragile. Most
notably, the C stubs end up in the file generated by
`CodeOutput.outputForeignStubs`, which is tuned towards
generating a file for stubs coming from `capi` and Haskell-to-C
exports.

Reviewers: simonmar, austin, goldfire, facundominguez, dfeuer, bgamari

Reviewed By: dfeuer, bgamari

Subscribers: snowleopard, rwbarton, dfeuer, thomie, duncan, mboes

Differential Revision: https://phabricator.haskell.org/D3280

1 files changed, 16 insertions, 13 deletions

diff --git a/libraries/template-haskell/Language/Haskell/TH/Syntax.hs b/libraries/template-haskell/Language/Haskell/TH/Syntax.hs
index c531eeffd7..466834a9a4 100644
--- a/libraries/template-haskell/Language/Haskell/TH/Syntax.hs
+++ b/libraries/template-haskell/Language/Haskell/TH/Syntax.hs
@@ -27,6 +27,7 @@ module Language.Haskell.TH.Syntax
     ( module Language.Haskell.TH.Syntax
       -- * Language extensions
     , module Language.Haskell.TH.LanguageExtensions
+    , ForeignSrcLang(..)
     ) where
 
 import Data.Data hiding (Fixity(..))
@@ -40,6 +41,7 @@ import Data.Word
 import Data.Ratio
 import GHC.Generics     ( Generic )
 import GHC.Lexeme       ( startsVarSym, startsVarId )
+import GHC.ForeignSrcLang.Type
 import Language.Haskell.TH.LanguageExtensions
 import Numeric.Natural
 
@@ -92,7 +94,7 @@ class Monad m => Quasi m where
 
   qAddTopDecls :: [Dec] -> m ()
 
-  qAddCStub :: String -> m ()
+  qAddForeignFile :: ForeignSrcLang -> String -> m ()
 
   qAddModFinalizer :: Q () -> m ()
 
@@ -133,7 +135,7 @@ instance Quasi IO where
   qRecover _ _          = badIO "recover" -- Maybe we could fix this?
   qAddDependentFile _   = badIO "addDependentFile"
   qAddTopDecls _        = badIO "addTopDecls"
-  qAddCStub    _        = badIO "addCStub"
+  qAddForeignFile _ _   = badIO "addForeignFile"
   qAddModFinalizer _    = badIO "addModFinalizer"
   qGetQ                 = badIO "getQ"
   qPutQ _               = badIO "putQ"
@@ -459,24 +461,25 @@ addDependentFile fp = Q (qAddDependentFile fp)
 addTopDecls :: [Dec] -> Q ()
 addTopDecls ds = Q (qAddTopDecls ds)
 
--- | Add an additional C stub. The added stub will be built and included in the
--- object file of the current module.
+-- | Emit a foreign file which will be compiled and linked to the object for
+-- the current module. Currently only languages that can be compiled with
+-- the C compiler are supported, and the flags passed as part of -optc will
+-- be also applied to the C compiler invocation that will compile them.
 --
--- Compilation errors in the given string are reported next to the line of the
--- enclosing splice.
+-- Note that for non-C languages (for example C++) @extern "C"@ directives
+-- must be used to get symbols that we can access from Haskell.
 --
--- The accuracy of the error location can be improved by adding
--- #line pragmas in the argument. e.g.
+-- To get better errors, it is reccomended to use #line pragmas when
+-- emitting C files, e.g.
 --
 -- > {-# LANGUAGE CPP #-}
 -- > ...
--- > addCStub $ unlines
+-- > addForeignFile LangC $ unlines
 -- >   [ "#line " ++ show (__LINE__ + 1) ++ " " ++ show __FILE__
 -- >   , ...
 -- >   ]
---
-addCStub :: String -> Q ()
-addCStub str = Q (qAddCStub str)
+addForeignFile :: ForeignSrcLang -> String -> Q ()
+addForeignFile lang str = Q (qAddForeignFile lang str)
 
 -- | Add a finalizer that will run in the Q monad after the current module has
 -- been type checked. This only makes sense when run within a top-level splice.
@@ -521,7 +524,7 @@ instance Quasi Q where
   qRunIO              = runIO
   qAddDependentFile   = addDependentFile
   qAddTopDecls        = addTopDecls
-  qAddCStub           = addCStub
+  qAddForeignFile     = addForeignFile
   qAddModFinalizer    = addModFinalizer
   qGetQ               = getQ
   qPutQ               = putQ