Question

I have a function as such:

int foo(void *val){
(char *)val="Long String";
return 0;
}

This function is called like:

char str[25];
foo(str);
printf("%s",str);

I get nothing printed out for some reason. what is wrong here?

Answer 1

You store the pointer to "Long String" into a variable val which is allocated on the stack. The lifetime of the variable extends only during the call to foo().

You don’t want to store the address to "Long String" on the stack. You want to copy the string under the provided address.

You should do this instead:

int foo(void *val){
  strcpy((char*)val, "Long String");
  return 0;
}

This isn’t safe, though. You should pass the maximum size of the buffer into foo and use strncpy() instead of strcpy().