On 11/9/22 02:18, Jakub Jelinek wrote:
On Tue, Nov 08, 2022 at 01:40:03PM -1000, Jason Merrill wrote:
A comment in D2552R1:
"The only questionable (but still conforming) case we found was
[[carries_dependency(some_argument)]] on GCC, where the emitted diagnostic said
that the
carries_dependency attribute is not supported, but did not specifically call
out the syntax error
in the argument clause."
made me try the following patch, where we'll error at least
for arguments to the attribute and for some uses of the attribute
appertaining to something not mentioned in the standard warn
with different diagnostics (or should that be an error?; clang++
does that, but I think we never do for any attribute, standard or not).
The diagnostics on toplevel attribute declaration is still an
attribute ignored warning and on empty statement different wording.
The paper additionally mentions
struct X { [[nodiscard]]; }; // no diagnostic on GCC
and 2 cases of missing diagnostics on [[fallthrough]] (guess I should
file a PR about those; one problem is that do { ... } while (0); there
is replaced during genericization just by ... and another that
[[fallthrough]] there is followed by a label, but not user/case/default
label, but an artificial one created from while loop genericization.
Thoughts on this?
LGTM.
Thanks, committed now.
Given CWG2538, I wonder whether we shouldn't at least pedwarn rather than
warning{,_at} for standard attributes that appertain to wrong entities
(and keep warning{,_at} for non-standard attributes including gnu variants
of standard attributes).
I don't think that's necessary, but it might be better. And I guess we
should separate the warnings for unrecognized attributes vs. misused
attributes.
If yes, we'd need to differentiate between the standard attributes
and gnu variants thereof (I think the C FE does, but C++ FE has
/* We used to treat C++11 noreturn attribute as equivalent to GNU's,
but no longer: we have to be able to tell [[noreturn]] and
__attribute__((noreturn)) apart. */
/* C++14 deprecated attribute is equivalent to GNU's. */
if (is_attribute_p ("deprecated", attr_id))
TREE_PURPOSE (TREE_PURPOSE (attribute)) = gnu_identifier;
/* C++17 fallthrough attribute is equivalent to GNU's. */
else if (is_attribute_p ("fallthrough", attr_id))
TREE_PURPOSE (TREE_PURPOSE (attribute)) = gnu_identifier;
/* C++23 assume attribute is equivalent to GNU's. */
else if (is_attribute_p ("assume", attr_id))
TREE_PURPOSE (TREE_PURPOSE (attribute)) = gnu_identifier;
so we'd need to remove that and make sure those standard attributes
are handled.
Jakub
