https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105646
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Summary|g++ does not raise "xxx is |g++ does not raise "xxx may
|used uninitialized" warning |be used uninitialized"
|under some conditions |warning on dead code when
| |optimizing
Last reconfirmed| |2022-08-19
Component|c++ |tree-optimization
Assignee|unassigned at gcc dot gnu.org |rguenth at gcc dot
gnu.org
Ever confirmed|0 |1
Status|UNCONFIRMED |ASSIGNED
--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
The issue is that for f3() we'd emit a may-uninitialized warning because f1()
could have thrown and thus v3{v3} is only executed conditionally. For f2()
v2{v2} is always executed (when f2 is entered). The late diagnostic pass
that would emit may-uninitialized warnings doesn't get to see the v3{v3}
initialization because it was removed as dead code.
When not optimizing we choose to diagnose may-uninit before eliminating v3{v3}.
Confirmed. Not sure if we want to fix this. We eventually might use a
different predicate than post-domination for whether a stmt is considered
always executed (ignoring EH and abnormal control flow). Greedily
following "fallthru" edges might work for this, also implementing the
unreachable edge honoring the ??? comment says.
I have a patch.
