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Defined in header <cstdlib> | ||
void free(void* ptr); | ||
Deallocates the space previously allocated bystd::malloc,std::calloc,std::aligned_alloc(since C++17), orstd::realloc.
Ifptr is a null pointer, the function does nothing.
The behavior is undefined if the value ofptr does not equal a value returned earlier bystd::malloc,std::calloc,std::aligned_alloc(since C++17), orstd::realloc.
The behavior is undefined if the memory area referred to byptr has already been deallocated, that is,std::free orstd::realloc has already been called withptr as the argument and no calls tostd::malloc,std::calloc,std::aligned_alloc(since C++17), orstd::realloc resulted in a pointer equal toptr afterwards.
The behavior is undefined if afterstd::free returns, an access is made through the pointerptr (unless another allocation function happened to result in a pointer value equal toptr).
The following functions are required to be thread-safe:
Calls to these functions that allocate or deallocate a particular unit of storage occur in a single total order, and each such deallocation callhappens-before the next allocation (if any) in this order. | (since C++11) |
Contents |
| ptr | - | pointer to the memory to deallocate |
(none)
The function accepts (and does nothing with) the null pointer to reduce the amount of special-casing. Whether allocation succeeds or not, the pointer returned by an allocation function can be passed tostd::free.
#include <cstdlib> int main(){int* p1=(int*)std::malloc(10* sizeof*p1); std::free(p1);// every allocated pointer must be freed int* p2=(int*)std::calloc(10, sizeof*p2);int* p3=(int*)std::realloc(p2,1000* sizeof*p3);if(!p3)// p3 null means realloc failed and p2 must be freed. std::free(p2); std::free(p3);// p3 can be freed whether or not it is null.}
C documentation forfree |
