wchar_t与GCC有多大？ [英] How big is wchar_t with GCC?

问题描述

GCC支持-fshort-wchar将wchar_t从4切换到两个字节。

GCC supports -fshort-wchar that switches wchar_t from 4, to two bytes.

在编译时检测wchar_t大小的最佳方法是什么，我可以正确映射到适当的utf-16或utf-32类型？
至少，直到c ++ 0x被释放，并给我们稳定的utf16_t和utf_32_t typedefs。

What is the best way to detect the size of wchar_t at compile time, so I can map it correctly to the appropriate utf-16 or utf-32 type? At least, until c++0x is released and gives us stable utf16_t and utf_32_t typedefs.

#if ?what_goes_here?
  typedef wchar_t Utf32;
  typedef unsigned short Utf16;
#else
  typedef wchar_t Utf16;
  typedef unsigned int Utf32;
#endif

推荐答案

__WCHAR_MAX__
__WCHAR_TYPE__

它们由gcc定义。您可以使用 echo|检查它们的值gcc -E - -dM

They are defined by gcc. You can check their value with echo "" | gcc -E - -dM

由于 __ WCHAR_TYPE __ 的值可以从 int 到 short unsigned int 或 long int 您的测试是IMHO检查 __ WCHAR_MAX __ 是否高于2 ^ 16。

As the value of __WCHAR_TYPE__ can vary from int to short unsigned int or long int, the best for your test is IMHO to check if __WCHAR_MAX__ is above 2^16.

#if __WCHAR_MAX__ > 0x10000
  typedef ...
#endif

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