将字符串数组分配给char **

Question

I just cannot assign string array to my char** pointer.

I have my strings in char *tempArr[12];

But I don't know how to assign them to my char** arr variable.

First, I allocate memory using: arr = (char**)malloc(numberOfElements * sizeof(char*));

Then I tried to allocate memory to each element:

arr[i] = malloc(256 * sizeof(char));

I also tried to alocate just the memory for char pointer but neither works. The result in my arr variable is 2 to 3 nonsense characters.

What could be wrong? I tried everything I was able to find and the result is either crash or nonsense content.

EDIT: Sorry I'll try to clarify it more. Background is, I am loading data from file into structs. Each struct has char** variable that is suppose to hold strings array.

In my reading code, I am using my temp array char* tempArr[12] and successfully loading strings into it. Then I pass it allong to my function that is creating my structs.

The problem starts here, I was trying to "convert" my passed array so it can be stored in char** arr variable.

Answer 1

char *tempArr[12];

Is array of pointers. So if you have something like

tempArr[0] = malloc(20);
strcpy(tempArr[0],"hello");

Then after what you are doing you can do. ie After allocating memory to your the pointer arr[i]

char **arr = malloc(numberOfElements * sizeof(char*));

arr[i] = malloc(256);

strcpy(arr[i],tempArr[0]);

You can run the above steps in a loop to copy values for all your pointers

Answer 2

I think that you mean the following

#include <string.h>

//...

size_t i;

char **arr = ( char** )malloc( numberOfElements * sizeof( char* ) );
for ( i = 0; i < numberOfElements; i++ ) arr[i] = malloc( 256 * sizeof( char ) );

for ( i = 0; i < sizeof( tempArr ) / sizeof( *tempArr ); i++ ) strcpy( arr[i], tempArr[i] );