[Bug c/45821] Missed -Wreturn-local-addr when local variable address comes from within a statement expression

[egallager at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=45821

Eric Gallager <egallager at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Blocks|                            |90556
            Summary|no warning when returning a |Missed -Wreturn-local-addr
                   |local variable address      |when local variable address
                   |within a statement          |comes from within a
                   |expression                  |statement expression

--- Comment #6 from Eric Gallager <egallager at gcc dot gnu.org> ---
(In reply to Manuel López-Ibáñez from comment #4)
> (In reply to Andrew Gaul from comment #3)
> > int *function_return_local(void)
> > {
> >     int x = 0;
> >     return &x;
> > }
> > 
> > int *statement_expression_return_local(void)
> > {
> >     int *y = ({
> >         int x = 0;
> >         &x;
> >     });
> >     return y;
> > }
> 
> We now warn at -O2:
> 
> test.c:14:10: warning: function returns address of local variable
> [-Wreturn-local-addr]
>    return y;
>           ^
> test.c:11:11: note: declared here
>        int x = 0;
>            ^
> 
> but only because we return y. For this testcase,
> 
> int statement_expression_return_local(void)
> {
>     int *y = ({
>         int x = 0;
>         &x;
>     });
>     return *y;
> }
> 
> we get: 
> 
> test.c:14:10: warning: ‘x’ is used uninitialized in this function
> [-Wuninitialized]
>    return *y;
>           ^
> 
> which is a bit confusing (and not the same warning).

It'd be good to get it from the same warning, so I'm making this block the
-Wreturn-local-addr meta-bug

> 
> Possibly related to 60517.
> it would be good to add the testcase


Referenced Bugs:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90556
[Bug 90556] [meta-bug] bogus/missing -Wreturn-local-addr