cd0b94e650
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. From-SVN: r272186 |
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| basic_string | ||
| basic_string_view | ||
| c_strings | ||
| char_traits/requirements | ||
| debug | ||
| headers | ||