Re: malloc/free aimple question!
"Robby" <Robby@discussions.microsoft.com> wrote in message
news:1E1CFF95-1304-4AA9-86DD-7822123D512C@microsoft.com...
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?
No. In fact it *must* not be freed.
The call to malloc() call gives your program ownership of a certain area of
memory. The call to free() relinquishes that ownership.
While you own it you can have as many pointers as you like pointing there.
But be careful, once you free the memory ALL of those pointers become
invalid and potentially dangerous, and so gratuitously duplicating pointers
is bad style. For example free(x) after free(p) would be trying to free
memory you no longer own, and would probably result in disaster.
(And in C++ new/delete are usually preferred to malloc/free. But the same
considerations apply.)
Dave
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