On 02/17/2017 09:53 PM, Jason Merrill wrote:
On Thu, Feb 16, 2017 at 6:13 PM, Martin Sebor <mse...@gmail.com> wrote:
On 02/16/2017 12:49 PM, Jason Merrill wrote:
On Thu, Feb 16, 2017 at 11:33 AM, Jakub Jelinek <ja...@redhat.com> wrote:
PR c++/79502
* pt.c (apply_late_template_attributes): If there are
no dependent attributes, set *p to attributes. If there were
some attributes in *p previously with or without dependent
attributes, chain them after the new attributes.
Here's the variant of your patch that I'm applying.
Sorry to butt in but I feel like I'm missing something basic. Are
these attributes (nodiscard, noreturn, maybe_unused, and deprecated)
meant to apply to templates? The text in for nodiscard suggests
they're not:
The attribute-token nodiscard may be applied to the declarator-id
in a function declaration or to the declaration of a class or
enumeration.
Noreturn also doesn't mention templates:
The attribute may be applied to the declarator-id in a function
declaration.
Deprecated explicitly mentions template specializations but not
primary templates:
The attribute may be applied to the declaration of a class,
a typedef-name, a variable, a non-static data member, a function,
a namespace, an enumeration, an enumerator, or a template
specialization.
I can certainly see how applying attributes to the primary template
would be useful so it's puzzling to me that the standard seems to
preclude it.
I don't think it's precluded; a /template-declaration/ syntactically
includes a /declaration/, so in general any statement about e.g. a
function declaration also applies to a function template declaration.
I'm sure you're right that it's not meant to be precluded, otherwise
the standard library couldn't declare noreturn the throw_with_nested
function template (the only template declared noreturn in the library
I could find).
FWIW, a context where noreturn clearly is not applicable is function
pointers. G++ accepts it there but then ignores it. Clang rejects
it. I would think accepting it on function pointers would be useful
as well. GCC (in C mode) accepts __attribute__ noreturn on function
pointers and treats them as such (G++ does not).
Another interesting context is the explicit instantiation directive.
Again, the standard seems clear that noreturn isn't allowed but GCC
and Microsoft Visual C++ both accept it. Clang and EDG reject it.
I think rejecting it here makes sense and accepting is a bug.
I ask also because I was just looking at bug 79021 and scratching
my head about what to thing about it. While trying to understand
how GCC handles attributes for the primary template I came across
what doesn't make sense to me. Why would it apply the attribute
from the primary to the explicit specialization when the two are
distinct entities? Is that a bug?
This seems like a Core issue; the standard says nothing about how
attributes on a template affect specializations.
Yes, I thought so as well. Thanks for confirming that. Unless
you would prefer to bring it up yourself let me post it to the
core reflector and suggest to open a new issue for it.
I think that as a general rule, not applying attributes from the
template to specializations makes sense. There will be some
exceptions, such as the abi_tag attribute which is a property of the
name rather than a particular declaration.
That makes sense to me.
Thanks
Martin
