diff -r 626fcf4a803e -r cef738d55348 src/HOL/Tools/Quickcheck/narrowing_generators.ML
--- a/src/HOL/Tools/Quickcheck/narrowing_generators.ML	Mon Mar 21 14:46:59 2011 +0100
+++ b/src/HOL/Tools/Quickcheck/narrowing_generators.ML	Mon Mar 21 16:38:28 2011 +0100
@@ -144,10 +144,9 @@
         val _ = File.write narrowing_engine_file narrowing_engine
         val _ = File.write main_file main
         val executable = File.shell_path (Path.append in_path (Path.basic "isa_lsc"))
-        val cmd = "\"$ISABELLE_GHC\" -fglasgow-exts " ^
+        val cmd = "( exec \"$ISABELLE_GHC\" -fglasgow-exts " ^
           (space_implode " " (map File.shell_path [code_file, narrowing_engine_file, main_file])) ^
-          " -o " ^ executable ^ " && " ^ executable
-          (* FIXME: should use bash command exec but does not work with && *) 
+          " -o " ^ executable ^ "; ) && " ^ executable
       in
         bash_output cmd
       end