C++ 表示 uint64_t 最大值的宏
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Macro representing maximum value for uint64_t
提问by Subway
I'm seeking for a macro representing the maximum value of uint64_tas UINT_MAXis for unsigned int.
i.e. I need this value to guaranteed to be (1<<64)-1.
我正在寻找一个表示uint64_tas UINT_MAXis for的最大值的宏unsigned int。即我需要这个值保证为 (1<<64)-1。
I tried to use UINT64_MAX, but compiling with g++ results in:
我尝试使用UINT64_MAX，但使用 g++ 编译会导致：
'UINT64_MAX' was not declared in this scope
It's worth to mention that I have this line #define __STDC_LIMIT_MACROSin the code before using UINT64_MAX.
值得一提的是，#define __STDC_LIMIT_MACROS在使用UINT64_MAX.
I was surprised to not find helpful information around the web about it.
我很惊讶在网上找不到有关它的有用信息。
采纳答案by pmr
Using the cstdintheader portably can be quite a challenge (it is missing from some MSVC implementations). At the same time numeric_limits::max()can be hard to use without constexprand it is not actually required to work with uint64_t. If you don't care about those things too much, std::numeric_limits<uint64_t>::max()will most likely do the trick.
cstdint可移植地使用标头可能是一个很大的挑战（某些 MSVC 实现中缺少它）。同时，numeric_limits::max()没有constexpr它可能很难使用，实际上也不需要使用uint64_t. 如果你不太关心这些事情，std::numeric_limits<uint64_t>::max()很可能会成功。
Boost.Integerhas an implementation of cstdintand comes with an extra traits class to get a constant maximal value. A compliant implementation of cstdintshould also provide the macro UINT64_MAX, but I'm not sure about boost.
Boost.Integer有一个实现cstdint并带有一个额外的traits 类来获得一个恒定的最大值。的合规实现也cstdint应该提供宏UINT64_MAX，但我不确定提升。
