9.2 Memory Interface

Python PEP

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9.2 Memory Interface

The following function sets, modeled after the ANSI C standard, but specifying behavior when requesting zero bytes, are available for allocating and releasing memory from the Python heap:

void* PyMem_Malloc( size_t n): Allocates n bytes and returns a pointer of type void* to the allocated memory, or NULL if the request fails. Requesting zero bytes returns a distinct non-NULL pointer if possible, as if PyMem_Malloc(1) had been called instead. The memory will not have been initialized in any way.

void* PyMem_Realloc( void *p, size_t n): Resizes the memory block pointed to by p to n bytes. The contents will be unchanged to the minimum of the old and the new sizes. If p is NULL, the call is equivalent to PyMem_Malloc(n); else if n is equal to zero, the memory block is resized but is not freed, and the returned pointer is non-NULL. Unless p is NULL, it must have been returned by a previous call to PyMem_Malloc() or PyMem_Realloc().

void PyMem_Free( void *p): Frees the memory block pointed to by p, which must have been returned by a previous call to PyMem_Malloc() or PyMem_Realloc(). Otherwise, or if PyMem_Free(p) has been called before, undefined behavior occurs. If p is NULL, no operation is performed.

The following type-oriented macros are provided for convenience. Note that TYPE refers to any C type.

TYPE* PyMem_New( TYPE, size_t n): Same as PyMem_Malloc(), but allocates (n * sizeof(TYPE)) bytes of memory. Returns a pointer cast to TYPE*. The memory will not have been initialized in any way.

TYPE* PyMem_Resize( void *p, TYPE, size_t n): Same as PyMem_Realloc(), but the memory block is resized to (n * sizeof(TYPE)) bytes. Returns a pointer cast to TYPE*.

void PyMem_Del( void *p): Same as PyMem_Free().

In addition, the following macro sets are provided for calling the Python memory allocator directly, without involving the C API functions listed above. However, note that their use does not preserve binary compatibility accross Python versions and is therefore deprecated in extension modules.

PyMem_MALLOC(), PyMem_REALLOC(), PyMem_FREE().

PyMem_NEW(), PyMem_RESIZE(), PyMem_DEL().

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