std::size_t
| Defined in header <cstddef>
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| Defined in header <cstdio>
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| Defined in header <cstdlib>
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| Defined in header <cstring>
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| Defined in header <ctime>
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| Defined in header <cwchar>
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| typedef /*implementation-defined*/ size_t; |
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std::size_t is the unsigned integer type of the result of the sizeof operator as well as the sizeof... operator and the alignof operator (since C++11).
Notes
std::size_t can store the maximum size of a theoretically possible object of any type (including array). A type whose size cannot be represented by std::size_t is ill-formed (since C++14) On many platforms (an exception is systems with segmented addressing) std::size_t can safely store the value of any non-member pointer, in which case it is synonymous with std::uintptr_t.
std::size_t is commonly used for array indexing and loop counting. Programs that use other types, such as unsigned int, for array indexing may fail on, e.g. 64-bit systems when the index exceeds UINT_MAX or if it relies on 32-bit modular arithmetic.
When indexing C++ containers, such as std::string, std::vector, etc, the appropriate type is the member typedef size_type provided by such containers. It is usually defined as a synonym for std::size_t.
Example
#include <cstddef> #include <iostream> #include <array> int main() { std::array<std::size_t,10> a; for (std::size_t i = 0; i != a.size(); ++i) a[i] = i; for (std::size_t i = a.size()-1; i < a.size(); --i) std::cout << a[i] << " "; }
Output:
9 8 7 6 5 4 3 2 1 0
See also
| signed integer type returned when subtracting two pointers (typedef) | |
| byte offset from the beginning of a standard-layout type to specified member (function macro) |