realloc char array c language arm

Question

I'm new on C and embedded systems and I need to reallocate a variable type char which is an array by definition.

I have:

char payLoad[1];
chrNum = 16 + 
    strlen("\"message\":")          + 
    strlen(strMsg)                  +
    strlen(", \"status":")          +
    strlen(strStatus)               +
//here I need to realloc my payLoad to message size chrNum
// after using this information i need to come back the array to 1 again

Tried to use some examples as

  (realloc(payLoad, sizeof(char *) * chrNum))

But my program blocks in this line.

Answer 1

You have payload defined as a char array, and you can't resize an array defined at compile time. You need to define it as a pointer so you can dynamically allocate memory:

char *payLoad = NULL, *temp;
chrNum = 16 + 
    strlen("\"message\":")          + 
    strlen(strMsg)                  +
    strlen(", \"status":")          +
    strlen(strStatus);
temp = realloc(payLoad, chrNum + 1);
if (temp == NULL) {
    perror("realloc failed");
    exit(1);
}
payload = temp;