Pointer & amp; dynamic memory allocation, C language pointer

Pointer & dynamic memory allocation, C language pointer

Dynamic Memory Allocation Mechanism in C ++

C ++ uses new and delete to allocate and release dynamic memory on the stack.

Note. All pointers should be initialized.

If the dynamic memory to which the Pointer Points is released or does not point to a valid address, set the pointer to nullptr. Otherwise, the memory will leak.

Variable:

Double * pvalue {};

Pvalue = new double;

* Pvalue = 9.0;

Or

Double * pvalue {};

Pvalue = new double {9.0 };

Or merge into one sentence.

Double * pvalue {new double {9.0 }};

Delete pvalue;

Array:

Char * pstr {new char [20]};

Delete [] pstr;

Pstr = nullptr;

Can be initialized by the way: int * data {new int [10] {2, 3, 4 }};

Multi-dimensional array:

Double (* pbeans) [4] {};

Pbeans = new double [3] [4];

Or merge as one step: double (* pbeans) [4] {new double [3] [4]};

Delete [] pbeans;

Pbeans = nullptr;

 

Dynamic Memory Allocation Mechanism in C Language

Malloc:

Double * ptd;

Ptd = (double *) malloc (N * sizeof (double ));

Free (ptd );

Request N double-Type Spaces

 

　Calloc:

Long * newmem;

Newmem = (long *) calloc (N, sizeof (long ));

The first parameter is the number of memory units required, and the second parameter is the size of each unit in bytes. Calloc sets all parts of the block to 0.

 

　　Dynamic Memory Allocation in a variable-length array (VLA:

Int n = 5;

Int m = 6;

Int ar [n] [m]; // Variable Length Array

Int (* p1) [6];

Int (* p2) [m]; // Variable Length Array

P1 = (int (*) [6]) malloc (n * 6 * sizeof (int ));

P2 = (int (*) [m]) malloc (n * m * sizeof (int); // Variable Length Array

Note: columns must be specified during array transmission as parameters.

For example, double (int ar [] [6]);