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From: rtidd@ccels3.mitre.org (Randy Tidd)
Newsgroups: comp.lang.c
Subject: Question about malloc() and free()
Message-ID: <118073@linus.mitre.org>
Date: 24 Aug 90 18:48:23 GMT
Sender: usenet@linus.mitre.org
Reply-To: rtidd@ccels3.mitre.org (Randy Tidd)
Organization: The Mitre Corporation
Lines: 42

I ran into what I think is an interesting question, I hope someone can
help me out. I hope this hasn't been beaten to death around here, but
I haven't seen it recently.

Say I have a routine that allocates big block of memory and returns a
pointer to it, something like:

char *get_chars()
{
  char *big_block;
  int i;

  big_block = malloc(10001);
  for(i=0; i<10000; i++)
    big_block[i] = getchar();
  big_block[i] = '\0';         /* NULL-terminate the array */
  return(big_block);
]

And the calling function does something like:

main()
{
  char foo[10001];

  strcpy(foo,get_chars());
  printf("%s\n",foo);    
}

What happens to the space that was malloc'ed? It is never freed by me;
will the compiler figure this out and arrange for it to be freed?  Is
the resolution method standard over compilers?

While this is an extreme case, I ran into something more moderate and
am curious, for performance reasons, of the turnout.

Any help is appreciated. Please e-mail me if you feel the rest of The
Net doesn't want to hear about it.
Randy Tidd				GOOD
rtidd@mwunix.mitre.org			FAST
#define DISCLAIM TRUE			CHEAP
						-pick any two