保证 char、wchar_t、char16_t、char32_t 上的大小排序
Guarantee on size ordering on char, wchar_t, char16_t, char32_t
C++ 标准是否对 char、wchar_t、char16_t、char32_t 的字节大小排序提供任何保证？ （欢迎从标准中提取任何内容）
例如，我是否可以保证：
sizeof(char) <= sizeof(wchar_t) <= sizeof(char16_t) <= sizeof(char32_t)
类型 char16_t 和 char32_t 分别定义为与 uint_least16_t 和 uint_least32_t 大小相同。
wchar_t 上不存在此类限制，除了它必须至少与 char 一样大（当然，all C 和 C++ 中的数据类型）。存在具有 1 字节、2 字节 (MSVC++) 和 4 字节 (GCC) 宽字符的实际实现。
是 1 == sizeof(char) <= sizeof(wchar_t) 和 1 == sizeof(char) <= sizeof(char16_t) <= sizeof(char32_t)。
5.3.3/1 大小[expr.sizeof]
... sizeof(char), sizeof(signed char) and sizeof(unsigned char) are 1.
... [ Note: in particular, sizeof(bool), sizeof(char16_t),
sizeof(char32_t), and sizeof(wchar_t) are implementation-defined.75 —
end note ].
3.9.1/5 基本类型 [basic.fundamental]
... Type wchar_t shall have the same size, signedness, and alignment
requirements (3.11) as one of the other integral types, called its
underlying type. Types char16_t and char32_t denote distinct types
with the same size, signedness, and alignment as uint_least16_t and
uint_least32_t, respectively, in <cstdint>, called the underlying
types.
更新：我没有在标准中找到它。 cppreference 表示 uint_leastN_t:
smallest unsigned integer type with width of at least 8, 16, 32 and 64
bits respectively
请注意 sizeof(char)==1 确实 而不是 意味着 char 有 8 位。另见 C++ FAQ. cppreference 关于 CHAR_BIT 的说法：
number of bits in byte
1.7/1 C++内存模型[intro.memory]
The fundamental storage unit in the C ++ memory model is the byte. A
byte is at least large enough to contain any member of the basic
execution character set (2.3) ...
在 64 位 Qt Creator（使用 Clang）中，wchar_t 是四 (4) 个字节。
C++ 标准是否对 char、wchar_t、char16_t、char32_t 的字节大小排序提供任何保证？ （欢迎从标准中提取任何内容）
例如，我是否可以保证：
sizeof(char) <= sizeof(wchar_t) <= sizeof(char16_t) <= sizeof(char32_t)
类型 char16_t 和 char32_t 分别定义为与 uint_least16_t 和 uint_least32_t 大小相同。
wchar_t 上不存在此类限制，除了它必须至少与 char 一样大（当然，all C 和 C++ 中的数据类型）。存在具有 1 字节、2 字节 (MSVC++) 和 4 字节 (GCC) 宽字符的实际实现。
是 1 == sizeof(char) <= sizeof(wchar_t) 和 1 == sizeof(char) <= sizeof(char16_t) <= sizeof(char32_t)。
5.3.3/1 大小[expr.sizeof]
... sizeof(char), sizeof(signed char) and sizeof(unsigned char) are 1. ... [ Note: in particular, sizeof(bool), sizeof(char16_t), sizeof(char32_t), and sizeof(wchar_t) are implementation-defined.75 — end note ].
3.9.1/5 基本类型 [basic.fundamental]
... Type wchar_t shall have the same size, signedness, and alignment requirements (3.11) as one of the other integral types, called its underlying type. Types char16_t and char32_t denote distinct types with the same size, signedness, and alignment as uint_least16_t and uint_least32_t, respectively, in <cstdint>, called the underlying types.
更新：我没有在标准中找到它。 cppreference 表示 uint_leastN_t:
smallest unsigned integer type with width of at least 8, 16, 32 and 64 bits respectively
请注意 sizeof(char)==1 确实 而不是 意味着 char 有 8 位。另见 C++ FAQ. cppreference 关于 CHAR_BIT 的说法：
number of bits in byte
1.7/1 C++内存模型[intro.memory]
The fundamental storage unit in the C ++ memory model is the byte. A byte is at least large enough to contain any member of the basic execution character set (2.3) ...
在 64 位 Qt Creator（使用 Clang）中，wchar_t 是四 (4) 个字节。