<format> use _MSVC_EXECUTION_CHARACTER_SET #2493
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For clang use ____clang_literal_encoding__, clang 14 will learn _MSVC_EXECUTION_CHARACTER_SET, but ____clang_literal_encoding__ is in clang 13. Additionally for the "slow path" get the "format codepage" using these new macros (at compile-time) rather than assuming the active codepage is the same as the execution character set.
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jovibor
reviewed
Jan 20, 2022
Remember to actually write code that compiles under clang :/
StephanTLavavej
requested changes
Jan 28, 2022
StephanTLavavej
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Jan 28, 2022
CaseyCarter
requested changes
Jan 28, 2022
StephanTLavavej
approved these changes
Jan 29, 2022
CaseyCarter
approved these changes
Jan 29, 2022
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I'm mirroring this to the MSVC-internal repo - please notify me if any further changes are pushed. |
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Thanks for this significant performance improvement! 🚀 🚀 😸 |
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This should drastically increase format's performance in the "default" case (still need to rerun my toy benchmarks though)
For clang use __clang_literal_encoding, clang 14 will learn
_MSVC_EXECUTION_CHARACTER_SET, but __clang_literal_encoding
is in clang 13.
Additionally for the "slow path" get the "format codepage" using
these new macros (at compile-time) rather than assuming the
active codepage is the same as the execution character set.
ABI Impact:
This changes which versions of some templates get used, and could cause ODR violations, but in general should make people's ABI situation better rather than worse.
In particular windows 1251 will now use the "fast path" on msvc, so if you link clang code (which always used the fast path) to
non-clang code you no longer have an ODR violation in std::foramt (although your codepages differ, so there are probably still relatively benign ODR violations elsewhere).
fixes: #2342