Re: malloc/free aimple question!

From:
=?Utf-8?B?Um9iYnk=?= <Robby@discussions.microsoft.com>
Newsgroups:
microsoft.public.vc.language
Date:
Wed, 5 Aug 2009 12:28:01 -0700
Message-ID:
<022436AD-0CC0-4B21-B5DB-8A0CCD00A9DB@microsoft.com>
Hello, David and Ben!

I am freeing p and leaving x alone. I was also tempted toset x to null, but
thats dangerous too... no!

Its just that in my real program, x and p are members of two different
structures which are typedefed in a header.

But my bug doesn't seem to point to a free() problem. I have to water down
the whole code again to see where this will end up. I have two winprocs. When
I go from the first winProc to the second one, and come back to the first
one, everything is ok. If I do the same thing but this time I remove a line
in the second winProc which has nothing to do with mallocing or freeing, when
I get back to the 1st winProc, and press a button twice... on the second
press, the program bombs catastrophically! I have a funny feeling I will
learn a good lesson on this one!

At this point I really can't give any usefull information until I get down
to what is really going on.

Thanks guys for your help. I will repost if I don't understand something else.

--
Best regards
Roberto

"Ben Voigt [C++ MVP]" wrote:

Robby wrote:

Hello,

Please view the code below:
========================
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int main()
{
int a;
long *p, *x;

p = malloc(10 * sizeof(long));
x = p;

for(a=0; a<9; a++)
{
// do stuff with x
*(x+a) = a;
}

free(p);
// other code here...
return 0;
}
===========================

In this case, does x have to be freed also?


You should not call free(x). But both x and p become invalid when you call
free(p), so don't use x any more either.

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