std::free - cppreference.com (original) (raw)
| | | | | ------------------------ | | | | void free( void* ptr ); | | |
Deallocates the space previously allocated by std::malloc, std::calloc, std::aligned_alloc(since C++17), or std::realloc.
If ptr is a null pointer, the function does nothing.
The behavior is undefined if the value of ptr does not equal a value returned earlier by std::malloc, std::calloc, std::aligned_alloc(since C++17), or std::realloc.
The behavior is undefined if the memory area referred to by ptr has already been deallocated, that is, std::free or std::realloc has already been called with ptr as the argument and no calls to std::malloc, std::calloc, std::aligned_alloc(since C++17), or std::realloc resulted in a pointer equal to ptr afterwards.
The behavior is undefined if after std::free returns, an access is made through the pointer ptr (unless another allocation function happened to result in a pointer value equal to ptr).
[edit] Parameters
| ptr | - | pointer to the memory to deallocate |
|---|
[edit] Return value
(none)
[edit] Notes
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 to std::free.
[edit] Example
#include 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. }