C allocation and release of storage space

Allocation and release of storage space

Data structures for dynamic storage allocation

header File #include <stdlib.h>

Dynamic storage allocation with four functions {malloc(),calloc(), realloc()} , the dynamic storage release: Free().

1.malloc(), dynamically allocating a memory space

void *malloc (unsigned int size)

Use sizeof() to calculate the size of the application space

Example:int *p= (int *) malloc (sizeof (int))

Request a storage space of type int, and convert the assigned address space address into an int type address assigned to the defined pointer variable P.

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2.calloc (), dynamically allocating contiguous memory space

void *calloc (unsigned int n,unsigned int size);

Memory requests N-length storage space for size bytes, and returns the starting position of the storage space, n is the number of elements, and size is the element storage length.

Example: int*p= (int*) calloc (10,sizeof (int));

equivalent to int *p= (int *) Mallo (sizeof (int) *10);

Example: assigning 26-character characters to an array using the CALLOC and malloc functions

Char *ch1= (char*) calloc (26,sizeof (char));

Char *ch2= (char*) malloc (sizeof (char[26]);

3.realloc Change the size of the pointer to the space

void *realloc (void *prt,size_t size)

Cases:

Change a floating-point space size to an integer size

Fdouble= (double*) malloc (sizeof (double));

Iint=realloc (fdouble,sizeof (int));

Program: Double type to short

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4.free (), freeing up storage space

void free (void *p)

No return value

Example: int *a;

*a= (int *) calloc (20,sizeof (int));

A=b;

b++;

Free (a);

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C allocation and release of storage space