Re: [I] [C++][FlightRPC][ODBC] Clang 20 compiles failed on macOS 26 [arrow]

["HuaHuaY (via GitHub)" <gi...@apache.org>]

HuaHuaY commented on issue #50756:
URL: https://github.com/apache/arrow/issues/50756#issuecomment-5142776199

   The second error is not easy to fix. We have these code which use deprecated `std::wstring_convert` and `std::codecvt_utf8`. #GH-46576 try to suppress compilation errors by adding `ARROW_SUPPRESS_DEPRECATION_WARNING`. But at least in my local environment, this error no longer occurs at the template definition, but rather where the template is actually instantiated.
   
   ```cpp
   // GH-46576: suppress unicode warnings
   ARROW_SUPPRESS_DEPRECATION_WARNING
   template <typename CHAR_TYPE>
   inline void WcsToUtf8(const void* wcs_string, size_t length_in_code_units,
                         std::vector<uint8_t>* result) {
     thread_local std::wstring_convert<std::codecvt_utf8<CHAR_TYPE>, CHAR_TYPE> converter;
     auto byte_string = converter.to_bytes((CHAR_TYPE*)wcs_string,
                                           (CHAR_TYPE*)wcs_string + length_in_code_units);
   
     uint32_t length_in_bytes = static_cast<uint32_t>(byte_string.size());
     const uint8_t* data = (uint8_t*)byte_string.data();
   
     result->reserve(length_in_bytes);
     result->assign(data, data + length_in_bytes);
   }
   ARROW_UNSUPPRESS_DEPRECATION_WARNING
   ```
   
   I think there are two ways to fix this:
   1. Wrap the `#include <codecvt>` and `#include <locale>` statements in `encoding.h` with `ARROW_SUPPRESS_DEPRECATION_WARNING`. Additionally, any code that includes both `encoding.h` and `<locale>` must include `encoding.h` first. This is necessary because the deprecation warning must be suppressed the moment the compiler encounters `<locale>` within the compilation unit. This is inconvenient, as headers like `<vector>` also internally include `<locale>`; effectively, if a compilation unit depends—directly or transitively—on `encoding.h`, `encoding.h` must be manually included at the very top of the source file.
   2. Replace this standard library API with the Boost `boost::locale::conv::utf_to_utf`.
   
   @kou @alinaliBQ What do you think about this?
   
   
   


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