< cpp‎ | types
Revision as of 23:36, 31 May 2013 by P12bot (Talk | contribs)

Type support
Basic types
Fundamental types
Fixed width integer types (C++11)
Numeric limits
C numeric limits interface
Runtime type information
Type traits
Type categories
Type properties
Type trait constants
Supported operations
Relationships and property queries
Type modifications
Type transformations
Defined in header <cstddef>
Defined in header <cstdio>
Defined in header <cstring>
Defined in header <ctime>
Defined in header <cwchar>
typedef /*implementation-defined*/ size_t;

std::size_t is the unsigned integer type of the result of the sizeof operator and the alignof operator.


std::size_t can store the maximum size of a theoretically possible object of any type (including array). On many platforms (an exception are 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.


#include <cstddef>
int main()
    const std::size_t N = 100;
    int* a = new int[N];
    for (std::size_t n = 0; n < N; ++n)
        a[n] = n;
    delete[] a;

See also

signed integer type returned when subtracting two pointers
(typedef) [edit]
byte offset from the beginning of a standard-layout type to specified member
(function macro) [edit]