C中的固定宽度整数文字？

Question

C 11首先引入了对通过用户定义的文本在C中定义新文本的支持。C 11或更高版本是否也为中的类型预先定义固定宽度整数文本的后缀？




Answer 1

否。从C 14开始，标准中定义的唯一文字后缀由

但是，可以很容易地定义自己的固定宽度文字如下：

#include <cstdint>

constexpr std::int8_t operator "" _int8(unsigned long long v)
{ return static_cast<std::int8_t>(v); }

constexpr std::uint8_t operator "" _uint8(unsigned long long v)
{ return static_cast<std::uint8_t>(v); }

constexpr std::int16_t operator "" _int16(unsigned long long v)
{ return static_cast<std::int16_t>(v); }

constexpr std::uint16_t operator "" _uint16(unsigned long long v)
{ return static_cast<std::uint16_t>(v); }

constexpr std::int32_t operator "" _int32(unsigned long long v)
{ return static_cast<std::int32_t>(v); }

constexpr std::uint32_t operator "" _uint32(unsigned long long v)
{ return static_cast<std::uint32_t>(v); }

constexpr std::int64_t operator "" _int64(unsigned long long v)
{ return static_cast<std::int64_t>(v); }

constexpr std::uint64_t operator "" _uint64(unsigned long long v)
{ return static_cast<std::uint64_t>(v); }

constexpr std::int_fast8_t operator "" _int_fast8(unsigned long long v)
{ return static_cast<std::int_fast8_t>(v); }

constexpr std::uint_fast8_t operator "" _uint_fast8(unsigned long long v)
{ return static_cast<std::uint_fast8_t>(v); }

constexpr std::int_fast16_t operator "" _int_fast16(unsigned long long v)
{ return static_cast<std::int_fast16_t>(v); }

constexpr std::uint_fast16_t operator "" _uint_fast16(unsigned long long v)
{ return static_cast<std::uint_fast16_t>(v); }

constexpr std::int_fast32_t operator "" _int_fast32(unsigned long long v)
{ return static_cast<std::int_fast32_t>(v); }

constexpr std::uint_fast32_t operator "" _uint_fast32(unsigned long long v)
{ return static_cast<std::uint_fast32_t>(v); }

constexpr std::int_fast64_t operator "" _int_fast64(unsigned long long v)
{ return static_cast<std::int_fast64_t>(v); }

constexpr std::uint_fast64_t operator "" _uint_fast64(unsigned long long v)
{ return static_cast<std::uint_fast64_t>(v); }

constexpr std::int_least8_t operator "" _int_least8(unsigned long long v)
{ return static_cast<std::int_least8_t>(v); }

constexpr std::uint_least8_t operator "" _uint_least8(unsigned long long v)
{ return static_cast<std::uint_least8_t>(v); }

constexpr std::int_least16_t operator "" _int_least16(unsigned long long v)
{ return static_cast<std::int_least16_t>(v); }

constexpr std::uint_least16_t operator "" _uint_least16(unsigned long long v)
{ return static_cast<std::uint_least16_t>(v); }

constexpr std::int_least32_t operator "" _int_least32(unsigned long long v)
{ return static_cast<std::int_least32_t>(v); }

constexpr std::uint_least32_t operator "" _uint_least32(unsigned long long v)
{ return static_cast<std::uint_least32_t>(v); }

constexpr std::int_least64_t operator "" _int_least64(unsigned long long v)
{ return static_cast<std::int_least64_t>(v); }

constexpr std::uint_least64_t operator "" _uint_least64(unsigned long long v)
{ return static_cast<std::uint_least64_t>(v); }

constexpr std::intmax_t operator "" _intmax(unsigned long long v)
{ return static_cast<std::intmax_t>(v); }

constexpr std::uintmax_t operator "" _uintmax(unsigned long long v)
{ return static_cast<std::uintmax_t>(v); }

constexpr std::intptr_t operator "" _intptr(unsigned long long v)
{ return static_cast<std::intptr_t>(v); }

constexpr std::uintptr_t operator "" _uintptr(unsigned long long v)
{ return static_cast<std::uintptr_t>(v); }

警告：如果将上述代码用于不适合无符号long的文字，则会无声地给出错误的结果，如果文字值不适合所请求的类型，则会产生溢出，例如999_int8。更好的实现（GPL-3许可）可能需要逐个字符解析文字，并在溢出时static_assert，如上所述。

使用用户定义的文字的缺点是，需要在后缀前面加下划线。，因为根据§17.6.4.3.4，不带下划线的后缀保留用于将来的标准化。