add test for #1679

testsuite/tests/ghc-regress/ccall/should_run/1679.hs

+{-# LANGUAGE ForeignFunctionInterface #-}
+import System.Mem
+import Foreign
+import Control.Exception
+
+-- Test for #1679.  If there's a GC during a foreign call, the
+-- interpreter could sometimes crash, because it was using the old
+-- pointer to the byte code instructions, which has now moved.  The
+-- tricky bit is allocating enough so that the old instructions are
+-- overwritten, hence performGC followed by sum [1..100000].
+
+foreign import ccall "wrapper" mkF :: IO () -> IO (FunPtr (IO ()))
+foreign import ccall "dynamic" call_F :: FunPtr (IO ()) -> IO ()
+
+main = do
+  fun <- mkF (do performGC
+                 print (sum [1..100000]))
+  call_F fun
+  putStrLn "ok"

testsuite/tests/ghc-regress/ccall/should_run/1679.stdout

+5000050000
+ok

testsuite/tests/ghc-regress/ccall/should_run/all.T

@@ -102,3 +102,6 @@ test('ffi018', only_ways(['ghci']), compile_and_run, ['ffi018_ghci_c.o'])
 clean(['ffi018_ghci_c.o'])
 
 test('ffi019', normal, compile_and_run, [''])
+
+# This one originally failed only GHCi, but doesn't hurt to test all ways.
+test('1679', normal, compile_and_run, [''])