test-resizing.c contains the following code in get_size():

  if (widthp)
    *widthp = width;
  if (*heightp)
    *heightp = height;


While the widthp check correctly checks the _pointer_ for non-NULL, the heightp check is against the _value_.
gcc with -O3 catches this mistake and aborts because of -Werror:

gcc -DHAVE_CONFIG_H -I. -I../.. -D_REENTRANT -I/home/sugar/sugar-jhbuild/install/include/gconf/2 -I/home/sugar/sugar-jhbuild/install/include
/dbus-1.0 -I/usr/include/gtk-2.0 -I/usr/lib/gtk-2.0/include -I/usr/include/atk-1.0 -I/usr/include/cairo -I/usr/include/pango-1.0 -I/usr/
include/glib-2.0 -I/usr/lib/glib-2.0/include -I/usr/include/pixman-1 -I/usr/include/freetype2 -I/usr/include/libpng12 -I/usr/include/
dbus-1.0 -I/usr/lib/dbus-1.0/include -I/usr/include/startup-notification-1.0 -O3 -ggdb -Wall -Wchar-subscripts -Wmissing-declarations
-Wmissing-prototypes -Wnested-externs -Wpointer-arith -Wcast-align -Wsign-compare -Wall -Werror -ansi -MT test-resizing.o -MD -MP -MF .deps/
test-resizing.Tpo -c -o test-resizing.o test-resizing.c
cc1: warnings being treated as errors
test-resizing.c: In function ‘main’:
test-resizing.c:82: error: ‘height’ is used uninitialized in this function
test-resizing.c:94: note: ‘height’ was declared here
make[4]: *** [test-resizing.o] Error 1
make[4]: Leaving directory `/home/sugar/sugar-jhbuild/source/metacity/src/wm-tester'