Thread: Returning Pointers - need some help

You can't return 'StreamClean', or a pointer to it, and expect to use it, because 'StreamClean' goes out of scope when the function ends. Either:
a) Make it static

Code:

static char StreamClean[FOO];

...

return StreamClean;

Which will preserve its scope, or:
b) Use malloc to dynamicly allocate memory you need, and return that. If you do so, you'll need to free said allocated memory when you're through with it:

Code:

char *StreamClean;

StreamClean = malloc( SOME_AMOUNT );

return StreamClean;

There are other interesting bits regarding the use of static, but I'll let you figure those out for yourself.

Quzah.

» How would I free the memory?
Well, as you may know, its a pointer. So you can free it anywhere you want, as long as its allocated. The reason is, pointers point to a memory address, no matter where your programs state is. For example:

Code:

char* foo(void) {
	char *ptr; // just a pointer to nothing

	ptr = (char *)malloc(25); // point to something

	strcpy(ptr, "This is a pointer"); // write to the memory

	return ptr; // return this memory address
}

int main() {
	char *p; // just a pointer to nothing

	p = foo(); // pickup the memory address, and set it to p

	free(p); // ptr [mask of p] now frees

	return 0;
}

Hope that makes sense,
- Stack Overflow

Personally most liked Thantos' s advice. And as an alternative, dont return anything(void). And just use in func then use the same pointers later.

CleanStream( pStr );
printf(pStr); // now it is different

Originally Posted by fizisyen

Personally most liked Thantos' s advice. And as an alternative, dont return anything(void). And just use in func then use the same pointers later.

CleanStream( pStr );
printf(pStr); // now it is different

The problem, as hinted at by Thantos, occurs if I do this, with his function:

Code:

char * CleanStream(char * Str )
{
  char *j, *k;
  for ( j = k = Str; *k != '\0'; k++)
    if ( *k != ' ' )
      *j++ = *k;
  *j = '\0';
  return Str;
}


int main( void )
{
    char *p;

    p = CleanStream( "Watch me crash your program!" );

    return 0;
}

Quzah.

yeah maybe you are right. I didnt tested any code this thread nor looked in to code, honestly. But i prefered because of working on pointer to original and returning the address approach. Surely, comparison to doing new arrays for this job. And at this manner, i am already thinking the same thing.

And, as i said already didnt test the above code you pointed. But, i suppose it is because of algorithm error.

Code:

    if ( *k != ' ' )
      *j++ = *k;
  *j = '\0';                   << here.

i suppose this is the place. In the first loop, putting NULL behind original string 2. char. And not controlling char. Useless. Not acceptable behavior. Needing an "else" statement. I suppose so. Maybe later will test this.

Regards

No i was wrong. Sorry. "j" is out of loop. Then i wonder why crashing.

No i was wrong. Sorry. "*j = '\0'" is out of loop. Then i wonder why crashing.

>>Then i wonder why crashing.
Because the original string is a string literal, which is most likely stored in read only memory.
http://www.eskimo.com/~scs/C-faq/q1.32.html