[PATCH] D28473: Implement http://wg21.link/P0426 Constexpr for std::char_traits

[Marshall Clow via Phabricator via cfe-commits]

mclow.lists created this revision.
mclow.lists added reviewers: EricWF, rsmith.
mclow.lists added a subscriber: cfe-commits.

Make `assign`/`length`/`find`/`compare` for `std::char_traits` constexpr.

This makes using `string_view`s at compile time easier.

Use the compiler intrinsics when available.
Note that `__builtin_memchr` is not really appropriate, since it returns a `void *`.
Sadly, this turns a bunch of code into "a twisty little maze of ifdefs, all different", but oh well.


https://reviews.llvm.org/D28473

Files:
  include/__string
  test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char/assign2.pass.cpp
  test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char/compare.pass.cpp
  test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char/find.pass.cpp
  test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char/length.pass.cpp
  test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char16_t/assign2.pass.cpp
  test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char16_t/compare.pass.cpp
  test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char16_t/find.pass.cpp
  test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char16_t/length.pass.cpp
  test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char32_t/assign2.pass.cpp
  test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char32_t/compare.pass.cpp
  test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char32_t/find.pass.cpp
  test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char32_t/length.pass.cpp
  test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.wchar.t/assign2.pass.cpp
  test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.wchar.t/compare.pass.cpp
  test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.wchar.t/find.pass.cpp
  test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.wchar.t/length.pass.cpp

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