pgf-shell: enable -rtsopts, call performGC between commands

This is to make it easier to find the cause of space leaks.

gf.cabal

@@ -255,6 +255,8 @@ executable pgf-shell
   hs-source-dirs:      src/runtime/haskell-bind/examples
   build-depends:       gf, base
   default-language:    Haskell2010
+  if impl(ghc>=7.0)
+    ghc-options: -rtsopts
 
 test-suite rgl-tests
   type:           exitcode-stdio-1.0

src/runtime/haskell-bind/examples/pgf-shell.hs

@@ -14,6 +14,7 @@ import System.IO.Error(catchIOError)
 import System.Environment
 import CRuntimeFFI
 import CId
+import System.Mem(performGC)
 
 main = getPGF =<< getArgs
 
@@ -21,7 +22,8 @@ getPGF [path] = pgfShell =<< readPGF path
 getPGF _ = putStrLn "Usage: pgf-shell <path to pgf>"
 
 pgfShell pgf =
-  forever $ do putStr "> "; hFlush stdout
+  forever $ do performGC
+               putStr "> "; hFlush stdout
                execute pgf =<< readLn
 
 execute pgf cmd =

src/runtime/haskell-bind/haskell-bind.cabal

@@ -31,3 +31,5 @@ executable pgf-shell
   hs-source-dirs:      examples
   build-depends:       base, haskell-bind
   default-language:    Haskell2010
+  if impl(ghc>=7.0)
+    ghc-options: -rtsopts