matlab mxrealloc函数语法

发表matlab mxrealloc函数相关文章
一句话说明: Reallocate dynamic memory using MATLAB memory manager

mxRealloc (C and Fortran)

Reallocate dynamic memory using MATLAB memory manager

C Syntax

#include "matrix.h"
#include <stdlib.h>
void *mxRealloc(void *ptr, mwSize size);

Fortran Syntax

mwPointer mxRealloc(ptr, size)
mwPointer ptr
mwSize size



Pointer to a block of memory allocated by mxCalloc, mxMalloc, or mxRealloc.


New size of allocated memory, in bytes.


Pointer to the start of the reallocated block of memory, if successful. If unsuccessful in a MAT or engine standalone application, mxRealloc returns NULL in C (0 in Fortran) and leaves the original memory block unchanged. (You must use mxFree to free the original memory block). If unsuccessful in a MEX-file, the MEX-file terminates and control returns to the MATLAB® prompt.

mxRealloc is unsuccessful when there is insufficient free heap space.


mxRealloc changes the size of a memory block that has been allocated with mxCalloc, mxMalloc, or mxRealloc. Use mxRealloc instead of the ANSI® C realloc function to allocate memory in MATLAB applications.

mxRealloc changes the size of the memory block pointed to by ptr to size bytes. The contents of the reallocated memory are unchanged up to the smaller of the new and old sizes. The reallocated memory might be in a different location from the original memory, so the returned pointer can be different from ptr. If the memory location changes, mxRealloc frees the original memory block pointed to by ptr.

If size is greater than 0 and ptr is NULL in C (0 in Fortran), mxRealloc behaves like mxMalloc, allocating a new block of memory of size bytes and returning a pointer to the new block.

If size is 0 and ptr is not NULL in C (0 in Fortran), mxRealloc frees the memory pointed to by ptr and returns NULL in C (0 in Fortran).

In MEX-files, but not MAT or engine applications, mxRealloc registers the allocated memory with the MATLAB memory manager. When control returns to the MATLAB prompt, the memory manager then automatically frees, or deallocates, this memory.

How you manage the memory created by this function depends on the purpose of the data assigned to it. If you assign it to an output argument in plhs[] using the mxSetPr function, MATLAB is responsible for freeing the memory.

If you use the data internally, the MATLAB memory manager maintains a list of all memory allocated by the function and automatically frees (deallocates) the memory when control returns to the MATLAB prompt. In general, we recommend that MEX-file functions destroy their own temporary arrays and free their own dynamically allocated memory. It is more efficient to perform this cleanup in the source MEX-file than to rely on the automatic mechanism. Therefore, when you finish using the memory allocated by this function, call mxFree to deallocate the memory.

If you do not assign this data to an output argument, and you want it to persist after the MEX-file completes, call mexMakeMemoryPersistent after calling this function. If you write a MEX-file with persistent memory, be sure to register a mexAtExit function to free allocated memory in the event your MEX-file is cleared.


See the following examples in matlabroot/extern/examples/mx.

See Also

mexAtExit, mexMakeArrayPersistent, mexMakeMemoryPersistent, mxCalloc, mxDestroyArray, mxFree, mxMalloc


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