[Bug tree-optimization/63446] dangling reference results in confusing diagnostic from -Wuninitialized

["msebor at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63446

Martin Sebor <msebor at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|2014-10-03 00:00:00         |2021-4-16
      Known to fail|                            |10.2.0, 11.0, 4.6.4, 4.9.4,
                   |                            |5.5.0, 6.4.0, 7.2.0, 8.3.0,
                   |                            |9.1.0
                 CC|                            |msebor at gcc dot gnu.org
           Severity|normal                      |enhancement
             Blocks|                            |49974

--- Comment #9 from Martin Sebor <msebor at gcc dot gnu.org> ---
GCC 11 improves the message by including a note that mentions the uninitialized
variable.  In this case it doesn't completely solve the problem because the
variable it points to is initialized but it should help.

pr63446.C: In function ‘int func()’:
pr63446.C:15:14: warning: ‘x’ is used uninitialized [-Wuninitialized]
   15 |     return f.ref;
      |              ^~~
pr63446.C:8:9: note: ‘x’ was declared here
    8 |     int x = 42;
      |         ^

But the underlying bug here is returning a reference to a local variable, so
the warning to improve is -Wreturn-local-addr.  That will diagnose the return
statement in make_foo().  Bug 49974 tracks that enhancement.  With that, the
additional -Wuninitialized issued in func() would just help clarify the
consequences of the bug but not otherwise be essential.


Referenced Bugs:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=49974
[Bug 49974] missing -Wreturn-local-addr for indirectly returning reference to
local/temporary