[Bug c/103649] -Wno-attribute=foo::bar implies no arguments

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103649

--- Comment #1 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The trunk branch has been updated by Marek Polacek <mpolacek@gcc.gnu.org>:

https://gcc.gnu.org/g:6afb8a68a9113897ccf39e40983e042ed90d7aed

commit r12-6052-g6afb8a68a9113897ccf39e40983e042ed90d7aed
Author: Marek Polacek <polacek@redhat.com>
Date:   Thu Dec 16 16:29:41 2021 -0500

    attribs: Fix wrong error with -Wno-attribute=A::b [PR103649]

    My patch to implement -Wno-attribute=A::b caused a bogus error when
    parsing

      [[foo::bar(1, 2)]];

    when -Wno-attributes=foo::bar was specified on the command line, because
    when we create a fake foo::bar attribute and insert it into our attribute
    table, it is created with max_length == 0 which doesn't allow any args.
    That is wrong -- we know nothing about the attribute, so we shouldn't
    require any specific number of arguments.  And since unknown attributes
    can be rather complex (see for example omp::{directive,sequence}), we
    must skip parsing their arguments.  To that end, I'm using max_length
    with value -2.

    Also let's not warn about things like

      [[vendor::assume(true)]];

    because they may have some meaning (this is reminiscent of C++ Portable
    Assumptions).

            PR c/103649

    gcc/ChangeLog:

            * attribs.c (handle_ignored_attributes_option): Create the fake
            attribute with max_length == -2.
            (attribute_ignored_p): New overloads.
            * attribs.h (attribute_ignored_p): Declare them.
            * tree-core.h (struct attribute_spec): Document that max_length
            can be -2.

    gcc/c/ChangeLog:

            * c-decl.c (c_warn_unused_attributes): Don't warn for
            attribute_ignored_p.
            * c-parser.c (c_parser_std_attribute): Skip parsing of the
attribute
            arguments when the attribute is ignored.

    gcc/cp/ChangeLog:

            * parser.c (cp_parser_declaration): Don't warn for
attribute_ignored_p.
            (cp_parser_std_attribute): Skip parsing of the attribute
            arguments when the attribute is ignored.

    gcc/testsuite/ChangeLog:

            * c-c++-common/Wno-attributes-6.c: New test.