YAP would break when gc was called from portray:

always save arguments before calling plwrite with possible portray
 only do it for portray because plwrite may be called from unsafe environments
 make Slot machinery mainstream.


git-svn-id: https://yap.svn.sf.net/svnroot/yap/trunk@637 b08c6af1-5177-4d33-ba66-4b1c6b8b522a

C/errors.c

@@ -181,7 +181,7 @@ DumpActiveGoals (void)
 	  DebugPutc (c_output_stream,'(');
 	  for (i= 0; i < arity; i++) {
 	    if (i > 0) DebugPutc (c_output_stream,',');
-	    plwrite(args[i], DebugPutc, 4);
+	    plwrite(args[i], DebugPutc, Handle_vars_f);
 	  }
 	  DebugPutc (c_output_stream,')');
 	}