trail_ref cleanup

git-svn-id: https://yap.svn.sf.net/svnroot/yap/trunk@64 b08c6af1-5177-4d33-ba66-4b1c6b8b522a

library/system.yap

@@ -282,8 +282,7 @@ check_mode(Mode, G) :-
 
 shell :-
 	G = shell,
-	get_shell(Shell),
-	atom_codes(FullCommand, Shell),
+	get_shell0(FullCommand),
 	exec_command(FullCommand, '$stream'(0),'$stream'(1), '$stream'(2), PID, Error),
 	handle_system_error(Error, off, G),
 	wait(PID, _Status, Error),
@@ -313,11 +312,18 @@ shell(Command, Status) :-
 	wait(PID, Status,Error),
 	handle_system_error(Error, off, G).
 
+get_shell0(Shell) :-
+	getenv('SHELL', Shell), !.
+get_shell0(Shell) :-
+	win,
+	getenv('COMSPEC', Shell0).
+
 get_shell(Shell) :-
 	getenv('SHELL', Shell0), !,
 	atom_codes(Shell0, Codes),
 	append(Codes," -c ", Shell).
 get_shell(Shell) :-
+	win,
 	getenv('COMPSEC', Shell0),
 	atom_codes(Shell0, Codes),
 	append(Codes," /c ", Shell).

library/system/sys.c

@@ -672,6 +672,16 @@ pid(void)
 #endif
 }
 
+static int
+win(void)
+{
+#if defined(__MINGW32__) || _MSC_VER
+  return(TRUE);
+#else
+  return(FALSE);
+#endif
+}
+
 static int
 p_kill(void)
 {
@@ -732,6 +742,7 @@ init_sys(void)
   UserCPredicate("rename_file", rename_file, 3);
   UserCPredicate("sleep", p_sleep, 2);
   UserCPredicate("error_message", error_message, 2);
+  UserCPredicate("win", win, 0);
 }
 
 #ifdef _WIN32