如何通过用户输入在堆上分配内存？

Question

Is there a way to create a function that can allocate a chunk of memory onto the heap where a caller can pass a size that they want to allocate and return a valid address for the caller to use? I know how to allocate a specific size but is there a way to have a caller pass the desired amount?

Answer 1

Absolutely: even in C malloc / calloc / realloc all take the size as their parameter, and they do not care where that size came from; same goes for new .

For example, if you would like to allocate a user-specified number of double s, you do this:

cout << "Enter the number of double elements that you want to allocate" << endl;
int count;
cin >> count;
// You can do this for C-style allocation...
double *chunkMalloc = malloc(sizeof(double)*count);
// ...or this for C++ style:
double *chunkNew = new double[count];
// Don't forget to free allocated chunks:
free(chunkMalloc);
delete[] chunkNew;