The signal is declared in GtkTestATContext with 0 parameters, but these handlers were written as if the signal had one `guint` parameter. On some architectures this accidentally works as intended, but on others (reproduced on i386 and riscv64) the test tries to use arbitrary stack contents as the `TestData *` and crashes when it tries to dereference the resulting non-pointer. Resolves: https://gitlab.gnome.org/GNOME/gtk/-/issues/6490 Signed-off-by: Simon McVittie <smcv@debian.org>