问题
I'd like to know the maximum value of size_t on the system my program is running. My first instinct was to use negative 1, like so:
size_t max_size = (size_t)-1;
But I'm guessing there's a better way, or a constant defined somewhere.
回答1:
A manifest constant (a macro) exists in C99 and it is called SIZE_MAX. There's no such constant in C89/90 though.
However, what you have in your original post is a perfectly portable method of finding the maximum value of size_t. It is guaranteed to work with any unsigned type.
回答2:
#define MAZ_SZ (~(size_t)0)
or SIZE_MAX
回答3:
As an alternative to bit-operations suggested in the other answers, you could do this in C++
#include <limits>
size_t maxvalue = std::numeric_limits<size_t>::max()
回答4:
The size_t max_size = (size_t)-1; solution suggested by the OP is definitely the best so far, but I did figure out another, more convoluted, way to do this. I'm posting it just for academic curiosity.
#include <limits.h>
size_t max_size = ((((size_t)1 << (CHAR_BIT * sizeof(size_t) - 1)) - 1) << 1) + 1;
回答5:
If you are assuming at least C++11 compiler then SIZE_MAX should be available to you:
http://en.cppreference.com/w/c/types/limits
来源：https://stackoverflow.com/questions/3472311/what-is-a-portable-method-to-find-the-maximum-value-of-size-t