The signal callbacks are defined to take pointers as their arguments, but the callbacks found in testsuite/gtk/builder.c are passing a GParamSpec by value as the second argument. This confuses and angers the compiler on ppc64el, resulting in segfaults after return from the function due to stack-smashing by the (completely-unused) argument. https://bugzilla.gnome.org/show_bug.cgi?id=721700