concatenating using C function to large char*

Question

I am trying to concatenate char* and const string but the system hangs. following is the code

unsigned long long size = 2*pow(10,18);
char* string = malloc(size);    
strcat(string," ");

I am not sure how to resolve the error. Using Dev c/c++ in windows 10.

Edit: Thank you for all your comments and answer. I have made the change in my code. But it still gives the same problem. It does not print the statement and still hangs.

char* string = malloc(20*sizeof(char));
if(string=NULL){
    printf("unsuccessful memory allocation");
}

strcat(string," ");

Answer 1

The most probable reason might be that malloc() might fail to allocate the amount of memory you request for . Always check if the memory is successfully allocated or not this way :

char *p; //some pointer
p=malloc(size*sizeof(char));

if(p==NULL)
{
    printf("unsuccessfull memory allocation");
    exit(1);
}

Note :

• malloc() returns the address of newly allocated memory on successful allocation .
• if memory allocation is not successful then, it returns NULL

---

And as @BLUEPIXY has mentioned in the comments, your strcat() will fail even if allocation is successful,

try initialize the string before using :

*string = 0; 

or copy string before strcat() function.

Answer 2

You are trying to allocate 20000000TB. You certainly don't have that much memory. malloc will be failing and returning a NULL pointer which you are then trying to write to!

Answer 3

I think that the cause of the fail is the size of memory you are trying to malloc.

unsigned long long size = 2*pow(10,18);

char* string = malloc(size);

you are trying to malloc: 2000000000000000000 bytes

Thats 2 EB (EB: exabyte) 1 EB = 1000000 GB