https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101582
Bug ID: 101582
Summary: C++ FE doesn't accept attribute-declaration
Product: gcc
Version: 12.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: jakub at gcc dot gnu.org
Target Milestone: ---
[[]];
is rejected by gcc (accepted by clang) in C++11 and later mode:
error: declaration does not declare anything [-fpermissive]
It is fine to warn about attributes we don't handle and throw away, like we
e.g.
on empty statements with attributes warn
attributes at the beginning of statement are ignored [-Wattributes]
except for the few like [[fallthrough]] or [[cold]], but we shouldn't reject it
with permerror.
I'll need it for OpenMP directives in attributes...
Implementation-wise, I think one option is in cp_parser_toplevel_declaration
after the
else if (token->type == CPP_SEMICOLON)
{
cp_lexer_consume_token (parser->lexer);
/* A declaration consisting of a single semicolon is invalid
* before C++11. Allow it unless we're being pedantic. */
if (cxx_dialect < cxx11)
pedwarn (input_location, OPT_Wpedantic, "extra %<;%>");
}
case try cp_parser_skip_std_attribute_spec_seq and if the token after it
is CPP_SEMICOLON, handle it as attribute-declaration, or faster but less clean
grammar-wise in cp_parser_simple_declaration detect the case where we have only
std attributes followed by semicolon and handle it there.
