Question

Possible Duplicate:
Trouble with returning a string from function
Can a local variable’s memory be accessed outside its scope?

I’m trying to use a function to modify the value of a String pointer. I declared a struct called someStruct, and one of the fields is a pointer to a string, named ‘valu’. Here’s what I did:

void func(char* nvalue,someStruct* container){
    char temp[strlen(nvalue+1);
    temp=strcpy(temp,nvalue);
    container->valu=temp;
    return;

Will this function modify the value of the container to be nvalue? If not, how can I do it? I’m really not good with C so any help would be nice! Thank you

Answer 1

Since tmp is a local variable, accessing to container->value outside of the function is an undefined behavior. However, it is possible to use dynamic allocation to control the lifetime of your variable.

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

char **p = &container->value;

*p = malloc(strlen(nvalue) + 1);

if (*p != NULL)
{
  strcpy(*p, nvalue);
}