[libcxx] Fix the type in __estimate_column_width

[stefanp]

Summary

It seems that we are using wchar_t in __estimate_column_width and assume that
it is a 32 bit type. However, on AIX 32 the size of wchar_t is only 16 bits.

Changed wchar_t to uint32_t since the variable is being passed to a function
that uses uint32_t anyway.

[hubert.reinterpretcast]

__utf32_character guards against usage of 16-bit wchar_t. The usage that gets broken by using wchar_t in the implementation is the char32_t case. There's no reason to tie the char32_t case to a UTF-32 wchar_t that I know of. The change LGTM.

Please wait for approval from the libc++ group.

[Mordante]

Thanks for the fix. I wasn't aware of other 16-bit wchar_t platforms other than Windows.
(Still this should have been uint32_t in the first place, as I did in other places.)

[stefanp]

Gentle ping: libc++

[mstorsjo]

Hi, this patch had failed tests in CI shown already during review (this test, which used to be XFAILed for windows no longer fails there), and those CI failures now show up for all other patches. Please pay attention to the CI status of your patches before pushing them, even if you’ve got approval for the patch!

libcxx/include/__format/parser_std_format_spec.h

 
 template <__utf32_character _CharT>
 _LIBCPP_HIDE_FROM_ABI constexpr __column_width_result<_CharT>
 __estimate_column_width(const _CharT* __first, const _CharT* __last,
                         size_t __maximum) noexcept {
   size_t __result = 0;
 
   while (__first != __last) {
-    wchar_t __c = *__first;
+    uint32_t __c = *__first;
     __result += __column_width(__c);
 
     if (__result > __maximum)
       return {__result - 2, __first};
 
     ++__first;
     if (__result >= __maximum)
       return {__result, __first};

libcxx/test/libcxx/utilities/format/format.string/format.string.std/std_format_spec_string_unicode.pass.cpp

 //===----------------------------------------------------------------------===//
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 // UNSUPPORTED: c++03, c++11, c++14, c++17
 // UNSUPPORTED: libcpp-no-concepts
 // UNSUPPORTED: libcpp-has-no-incomplete-format
 
-// Fails for 32-bit builds on AIX.
-// UNSUPPORTED: LIBCXX-AIX-FIXME
-
 // UTF-32 doesn't work properly
 // XFAIL: windows
 
 // <format>
 
 // Tests the Unicode width support of the standard format specifiers.
 // It tests [format.string.std]/8 - 11:
 // - Properly determining the estimated with of a unicode string.