We're passing integers without validating their size, and newer GCC are
very cross about it, with warnings like:
warning: argument 1 range [18446744071562067968, 18446744073709551615]
exceeds maximum object size 9223372036854775807 [-Walloc-size-larger-than=]
We should check we're not overflowing the allocation size, by limiting
the range of values we can use.
First of all, we need to use `gsize` instead of a random `int`, since we're
allocating data.
Additionally, we need to check that the multiplication that computes the
size of the allocation doesn't overflow the maximum value of a `gsize`.
Otherwise gcc complains when we use these as arguments to g_new() on
32bit architectures with:
../gtk/gtkcomposetable.c: In function ‘gtk_compose_table_list_add_array’:
/usr/include/glib-2.0/glib/gmem.h:217:10: warning: argument 1 range [2147483648, 4294967295] exceeds maximum object size 2147483647 [-Walloc-size-larger-than=]
__p = g_##func##_n (__n, __s); \
~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/glib-2.0/glib/gmem.h:279:42: note: in expansion of macro ‘_G_NEW’
#define g_new0(struct_type, n_structs) _G_NEW (struct_type, n_structs, malloc0)
^~~~~~
../gtk/gtkcomposetable.c:851:22: note: in expansion of macro ‘g_new0’
gtk_compose_seqs = g_new0 (guint16, length);
^~~~~~
/usr/include/glib-2.0/glib/gmem.h:96:10: note: in a call to allocation function ‘g_malloc0_n’ declared here
gpointer g_malloc0_n (gsize n_blocks,
^~~~~~~~~~~
People might put all sorts of gunk in their .XCompose file, in
the hope that XLib makes sense of it. Even if we don't make sense
of it, we shouldn't abort, but instead ignore the lines we can't
understand. Pointed out in
https://bugzilla.redhat.com/show_bug.cgi?id=1301254
