[Bug middle-end/103365] [12 Regression] ICE in register_scoped_attribute, with attribute starting with underscore: -Wno-attributes=n::_a or #pragma GCC diagnostic ignored_attributes "n::_a"

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103365

--- Comment #4 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Jakub Jelinek <jakub@gcc.gnu.org>:

https://gcc.gnu.org/g:709716b9f49f2fcf46f319000562cf6e61bd2f71

commit r12-5493-g709716b9f49f2fcf46f319000562cf6e61bd2f71
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Wed Nov 24 10:08:35 2021 +0100

    attribs: Fix ICEs on attributes starting with _ [PR103365]

    As the patch shows, we have quite a few asserts that we don't call
    lookup_attribute etc. with attr_name that starts with an underscore,
    to make sure nobody is trying to call it with non-canonicalized
    attribute name like "__cold__" instead of "cold".
    We canonicalize only attributes that start with 2 underscores and end
    with 2 underscores though.
    Before Marek's patch, that wasn't an issue, we had no attributes like
    "_foo" or "__bar_" etc., so lookup_scoped_attribute_spec would
    always return NULL for those and we wouldn't try to register them,
    look them up etc., just with -Wattributes would warn about them.
    But now, as the new testcases show, users can actually request such
    attributes to be ignored, and we ICE for those during
    register_scoped_attribute and when that is fixed, ICE later on when
    somebody uses those attributes because they will be looked up
    to find out that they should be ignored.

    So, the following patch instead of or in addition to, depending on
    how performance sensitive a particular spot is, checking that
    attribute doesn't start with underscore allows attribute
    names that start with underscore as long as it doesn't canonicalize
    (i.e. doesn't start and end with 2 underscores).
    In addition to that, I've noticed lookup_attribute_by_prefix
    was calling get_attribute_name twice unnecessarily, and 2 tests
    were running in c++98 mode with -std=c++98 -std=c++11 which IMHO
    isn't useful because -std=c++11 testing is done too when testing
    all language versions.

    2021-11-24  Jakub Jelinek  <jakub@redhat.com>

            PR middle-end/103365
            * attribs.h (lookup_attribute): Allow attr_name to start with
            underscore, as long as canonicalize_attr_name returns false.
            (lookup_attribute_by_prefix): Don't call get_attribute_name twice.
            * attribs.c (extract_attribute_substring): Reimplement using
            canonicalize_attr_name.
            (register_scoped_attribute): Change gcc_assert into
            gcc_checking_assert, verify !canonicalize_attr_name rather than
            that str.str doesn't start with '_'.

            * c-c++-common/Wno-attributes-1.c: Require effective target
            c || c++11 and drop dg-additional-options.
            * c-c++-common/Wno-attributes-2.c: Likewise.
            * c-c++-common/Wno-attributes-4.c: New test.
            * c-c++-common/Wno-attributes-5.c: New test.