https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93810
--- Comment #2 from CVS Commits ---
The master branch has been updated by Jason Merrill :
https://gcc.gnu.org/g:04dd734b52de121853e1ea6b3c197a598b294e23
commit r10-7424-g04dd734b52de121853e1ea6b3c197a598b294e23
Author: Martin Sebor
Date: Fri Mar 27 12:07:45 2020 -0400
c++: avoid -Wredundant-tags on a first declaration in use [PR 93824]
-Wredundant-tags doesn't consider type declarations that are also
the first uses of the type, such as in 'void f (struct S);' and
issues false positives for those. According to the reported that's
making it harder to use the warning to clean up LibreOffice.
The attached patch extends -Wredundant-tags to avoid these false
positives by relying on the same class_decl_loc_t::class2loc mapping
as -Wmismatched-tags. The patch also improves the detection
of both issues in template declarations.
gcc/cp/ChangeLog
2020-03-27 Martin Sebor
PR c++/94078
PR c++/93824
PR c++/93810
* cp-tree.h (most_specialized_partial_spec): Declare.
* parser.c (cp_parser_elaborated_type_specifier): Distinguish alias
from declarations.
(specialization_of): New function.
(cp_parser_check_class_key): Move code...
(class_decl_loc_t::add): ...to here. Add parameters. Avoid
issuing
-Wredundant-tags on first-time declarations in other declarators.
Correct handling of template specializations.
(class_decl_loc_t::diag_mismatched_tags): Also expect to be called
when -Wredundant-tags is enabled. Use primary template or partial
specialization as the guide for uses of implicit instantiations.
* pt.c (most_specialized_partial_spec): Declare extern.
gcc/testsuite/ChangeLog
2020-03-27 Martin Sebor
PR c++/94078
PR c++/93824
PR c++/93810
* g++.dg/warn/Wmismatched-tags-3.C: New test.
* g++.dg/warn/Wmismatched-tags-4.C: New test.
* g++.dg/warn/Wmismatched-tags-5.C: New test.
* g++.dg/warn/Wmismatched-tags-6.C: New test.
* g++.dg/warn/Wredundant-tags-3.C: Remove xfails.
* g++.dg/warn/Wredundant-tags-6.C: New test.
* g++.dg/warn/Wredundant-tags-7.C: New test.
