https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97222
Richard Smith <richard-gccbugzilla at metafoo dot co.uk> changed:
What |Removed |Added
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CC| |richard-gccbugzilla@metafoo
| |.co.uk
--- Comment #3 from Richard Smith <richard-gccbugzilla at metafoo dot co.uk> ---
> would be interesting to see how ICC mangles the aligned case
It doesn't, it just takes the properties from whichever instantiation happens
to be performed first. On ICC,
std::cout << alignof(typename identity<float>::type) << std::endl;
std::cout << alignof(typename identity<fp>::type) << std::endl;
prints 4 4, and
std::cout << alignof(typename identity<fp>::type) << std::endl;
std::cout << alignof(typename identity<float>::type) << std::endl;
prints 16 16. The ICC behavior seems unsound, compared to the GCC / Clang
behavior of (effectively) stripping the attribute from template arguments.
> There is NO way defined at this point to mange for some attributes
> including but not limited to may_alias and alignment.
These can be mangled as <extended-qualifier>s:
http://itanium-cxx-abi.github.io/cxx-abi/abi.html#mangle.qualified-type
Presumably the more problematic part from an ABI perspective is that this will
change a bunch of existing manglings. Similarly from a source compatibility
standpoint, making the alignment override part of the type would be a breaking
change. It'd probably be better to add a new syntax for the new functionality
(please, not based on an attributed typedef this time!) and deprecate the old
way.
