Use of triple pointer over double pointer when only reading value of double pointer?-CodePudding

This code only looks like this as the use of structs and global variables is prohibited in the assignment.

It works either way, but I was wondering whether only using a double pointer would reallocate a temporary copy of the pointer.

#include<stdio.h>
#include<string.h>
#include<stdlib.h>

void allocateData(char ***dptrArrayData, int *intArraySize)
{
    *dptrArrayData = (char**)malloc(*intArraySize*sizeof(char*));
    for (int i = 0; i < *intArraySize; i  )
    {
        (*dptrArrayData)[i] = (char*)malloc(12*sizeof(char));
        (*dptrArrayData)[i] = "Lorem Ipsum";
    }
}

void printDataDoublePointer(char **dptrArrayData, int intArraySize)
{
    for (int i = 0; i < intArraySize; i  )
    {
        printf("Text:%s at index:%d\n",dptrArrayData[i],i);
    }
}

void printDataTriplePointer(char ***dptrArrayData, int *intArraySize)
{
    for (int i = 0; i < *intArraySize; i  )
    {
        printf("Text:%s at index:%d\n",(*dptrArrayData)[i],i);
    }
}
int main()
{
    char **dptrArrayData;
    int intArraySize = 5;
    allocateData(&dptrArrayData,&intArraySize);
    printDataDoublePointer(dptrArrayData,intArraySize);
    printDataTriplePointer(&dptrArrayData,&intArraySize);
    return 0;
}

CodePudding user response：

It works either way, but I was wondering whether only using a double pointer would reallocate a temporary copy of the pointer.

I take you to be asking about the difference between

void printDataDoublePointer(char **dptrArrayData, int intArraySize)

and

void printDataTriplePointer(char ***dptrArrayData, int *intArraySize)

. In each case the function receives copies of all argument values presented by the caller. This is the essence of pass-by-value semantics, which are the only function-call semantics C provides.

But there is no reallocation involved. When a pointer is passed as a function argument, only the pointer is copied, not the object to which it points. The function receives an independent pointer to the same object the original points to.