Memory operations in Functions

1. Address Transfer Request memory problems.

Let's look at the following example.

Struct complex_t // plural {int real; // real int imag; // virtual number}; int create (complex_t * P, unsigned int N) {P = new complex_t [N]; // apply for N complexif (P = NULL) Return-1; else return 0 ;}

Then, call this function in the main function:

Complex_t * comps = NULL; If (create (comps, 10) <0) // call the function {printf ("create failed \ n"); Return-1 ;} if (comps = NULL) {cout <"comps is null \ n"; Return-1;} // other operations

The first parameter of the create function, type: complex_t *. Then, a bucket is allocated to P in create. The pointer is used as a parameter to return the applied memory address.
In fact, comps = NULL after execution.
When the create function is called in the main function, comps is assigned to P. That is, the pointer P points to the same storage space as comps. However, in create, P = new complex_t [N] Makes P point to a new bucket. At this time, comps still points to the original storage space. Therefore, the changes made to P in create have no impact on comps.
The parameter complex_t * in the create function can be compared to int as a whole.

Through the above analysis, it is not difficult to provide a solution:

Int create (complex_t ** P, unsigned int N) {* P = new complex_t [N]; // apply for N complexif (P = NULL) Return-1; else return 0 ;}