https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88466
James Y Knight <foom at fuhm dot net> changed:
What |Removed |Added
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CC| |foom at fuhm dot net
--- Comment #7 from James Y Knight <foom at fuhm dot net> ---
FWIW, the discussion in Clang about this is still ongoing, and the functions
remain unimplemented there.
I personally remain of the opinion that it would be ideal to leave these
permanently unimplemented, despite that the standards committee decided to keep
them in the standard even after objections were raised.
My second-favorite implementation after "unimplemented", would be to just
return constant values of 64 and 128 universally, regardless of architecture.
(If you cannot return an actually-correct answer, and decided that you need to
return something, you might as well just do something really easy and, _shrug_,
oh well.).
Others are arguing for implementing them to return actually valid and correct
values that depend on the exact configuration, and marking them as not being
abi-stable. Users would then need to be aware that they must not use the
constants in ABIs (which means effectively "don't use in a header file"), since
the value might change at any time with a compiler upgrade, or with the use of
different command-line flags (e.g. -mcpu/-march).
(To return correct values, compiler upgrades must be allowed to change the
values if it becomes aware of a new CPU model which changes the
largest/smallest-known cacheline sizes that this code could run on. And
-mcpu/-march flags similarly ought to change the values by restricting the
possible set of CPUs this code might run on.)
Any new thoughts from GCC developers?
