Created attachment 350907 [details] [review]
gdatetime: Fix overflow checks when constructing from timestamps

GDateTime does overflow checks to see if the timestamp being passed in
is too big to be represented. However, it only does those after
converting from a timestamp to an interval, which involves some
multiplications and additions — and hence can overflow, and cause the
later bounds check to erroneously succeed. This results in a non-NULL
GDateTime being returned which represents completely the wrong date.

Fix the overflow checks (do them earlier) and add some unit tests.

Signed-off-by: Philip Withnall <withnall@endlessm.com>

Review of attachment 350907 [details] [review]:

Looks generally good to me.

::: glib/gdatetime.c
@@ +653,3 @@
                               const GTimeVal *tv)
 {
+  if (tv->tv_sec > G_MAXINT64 - 1 ||

What happens if tv_sec is a 32 bit type? Do we care?

::: glib/tests/gdatetime.c
@@ +147,3 @@
+{
+  GDateTime *dt;
+

Would be nice to a reference to the bug, here.

Review of attachment 350907 [details] [review]:

::: glib/gdatetime.c
@@ +653,3 @@
                               const GTimeVal *tv)
 {
+  if (tv->tv_sec > G_MAXINT64 - 1 ||

Whoops, yes, we care. I’ll add some casts to fix this.

::: glib/tests/gdatetime.c
@@ +147,3 @@
+{
+  GDateTime *dt;
+

Good point. Added.

t branch -d 782089	
Pushed with the requested changes. Thanks for the review!

Attachment 350907 [details] pushed as 9374ecc - gdatetime: Fix overflow checks when constructing from timestamps

See https://bugzilla.gnome.org/show_bug.cgi?id=783841 - these new tests fail for 32 bit systems.