[PATCH] work harder to avoid -Wuninitialized for empty structs (PR 96295)

[Jeff Law]

On 9/15/20 1:00 PM, Martin Sebor via Gcc-patches wrote:
> The -Wuninitialized/-Wmaybe-uninitialized enhancement to warn when
> a pointer or reference to an uninitialized object is passed to
> a const-qualified function argument tries to avoid triggering for
> objects of empty types.  However, the suppression is incomplete
> and lets the warning trigger in some corner cases.  The attached
> patch extends the suppression to those as well.
>
> Tested on x86_64-linux.  I will plan to commit it later this week
> if there are no objections.
>
> Martin
>
> gcc-96295.diff
>
> Work harder to avoid -Wuninitialized for objects of empty structs (PR middle-end/96295).
>
> Resolves:
> PR middle-end/96295 - -Wmaybe-uninitialized warning for range operator with
> reference to an empty struct
>
> gcc/ChangeLog:
>
> 	PR middle-end/96295
> 	* tree-ssa-uninit.c (maybe_warn_operand): Work harder to avoid
> 	warning for objects of empty structs
>
> gcc/testsuite/ChangeLog:
>
> 	PR middle-end/96295
> 	* g++.dg/warn/Wuninitialized-11.C: New test.

FWIW, we had a build in Fedora rawhide fail just in the last couple
weeks because of the enhanced uninitialized warning.  I've already
forgotten the package, but it was a true positive, though sadly it was
just in the package's testsuite and thus we didn't actually find/fix a
user visible package bug.


OK for the trunk.  Thanks.


jeff


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