Hi,
On Wed, 12 Jun 2019 at 16:54, Jonathan Wakely <jwak...@redhat.com> wrote: > > The std::to_chars functions from C++17 can be used to implement > std::to_string with much better performance than calling snprintf. Only > the __detail::__to_chars_len and __detail::__to_chars_10 functions are > needed for to_string, because it always outputs base 10 representations. > > The return type of __detail::__to_chars_10 should not be declared before > C++17, so the function body is extracted into a new function that can be > reused by to_string and __detail::__to_chars_10. > > The existing tests for to_chars rely on to_string to check for correct > answers. Now that they use the same code that doesn't actually ensure > correctness, so add new tests for std::to_string that compare against > printf output. > > * include/Makefile.am: Add new <bits/charconv.h> header. > * include/Makefile.in: Regenerate. > * include/bits/basic_string.h (to_string(int), to_string(unsigned)) > (to_string(long), to_string(unsigned long), to_string(long long)) > (to_string(unsigned long long)): Rewrite to use __to_chars_10_impl. > * include/bits/charconv.h: New header. > (__detail::__to_chars_len): Move here from <charconv>. > (__detail::__to_chars_10_impl): New function extracted from > __detail::__to_chars_10. > * include/std/charconv (__cpp_lib_to_chars): Add, but comment out. > (__to_chars_unsigned_type): New class template that reuses > __make_unsigned_selector_base::__select to pick a type. > (__unsigned_least_t): Redefine as __to_chars_unsigned_type<T>::type. > (__detail::__to_chars_len): Move to new header. > (__detail::__to_chars_10): Add inline specifier. Move code doing the > output to __detail::__to_chars_10_impl and call that. > * include/std/version (__cpp_lib_to_chars): Add, but comment out. > * testsuite/21_strings/basic_string/numeric_conversions/char/ > to_string.cc: Fix reference in comment. Remove unused variable. > * testsuite/21_strings/basic_string/numeric_conversions/char/ > to_string_int.cc: New test. > > Tested x86_64-linux, committed to trunk. > The new test to_string_int.cc fails on arm-none-eabi: PASS: 21_strings/basic_string/numeric_conversions/char/to_string_int.cc (test for excess errors) spawn /aci-gcc-fsf/builds/gcc-fsf-gccsrc/obj-arm-none-eabi/gcc3/utils/bin/qemu-wrapper.sh ./to_string_int.exe /libstdc++-v3/testsuite/21_strings/basic_string/numeric_conversions/char/to_string_int.cc:105: void check_value(T) [with T = long long int]: Assertion 's == expected' failed. FAIL: 21_strings/basic_string/numeric_conversions/char/to_string_int.cc execution test Christophe
