Bug 840319: Keep js/src/gdb/gdb-tests.cpp's 'breakpoint' function from being unified with other functions in SM. r=sfink

js/src/gdb/gdb-tests.cpp

@@ -44,7 +44,13 @@ void reportError(JSContext *cx, const char *message, JSErrorReport *report)
 
 // prolog.py sets a breakpoint on this function; test functions can call it
 // to easily return control to GDB where desired.
-void breakpoint() {}
+void breakpoint() {
+    // If we leave this function empty, the linker will unify it with other
+    // empty functions throughout SpiderMonkey. If we then set a GDB
+    // breakpoint on it, that breakpoint will hit at all sorts of random
+    // times. So make it perform a distinctive side effect.
+    fprintf(stderr, "Called " __FILE__ ":breakpoint\n");
+}
 
 GDBFragment *GDBFragment::allFragments = NULL;