size_t
Defined in header <stddef.h>
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Defined in header <stdio.h>
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Defined in header <stdlib.h>
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Defined in header <string.h>
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Defined in header <time.h>
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Defined in header <uchar.h>
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(since C11) | |
Defined in header <wchar.h>
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(since C95) | |
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size_t
is the unsigned integer type of the result of sizeof , alignof (since C11) and offsetof
, depending on the data model.
Notes
size_t
can store the maximum size of a theoretically possible object of any type (including array).
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.
Example
#include <stdio.h>
#include <stddef.h>
#include <stdint.h>
int main(void)
{
const size_t N = 100;
int numbers[N];
for (size_t ndx = 0; ndx < N; ++ndx)
numbers[ndx] = ndx;
printf("SIZE_MAX = %zu\n", SIZE_MAX);
size_t size = sizeof numbers;
printf("size = %zu\n", size);
}
Possible output:
SIZE_MAX = 18446744073709551615
size = 400
See also
signed integer type returned when subtracting two pointers (typedef) | |
byte offset from the beginning of a struct type to specified member (function macro) |
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