On 16/08/16 05:16 +0000, Bernd Edlinger wrote:
Hi Jonathan,
I think this would be an improvement, although I still can't get the
assertion to fail:
Probably because the memory is still initialized to zero,
when it is used for the first time.
Yes, I did try allocating the same size block, setting it to something
non-zero, and freeing it again, but it was zero again when it got
reallocated (GCC is obviously too good at removing dead code :-)
Try this:
#include <stdlib.h>
#include <string.h>
#include <assert.h>
struct A
{
A() {}
void* operator new(size_t s)
{
void* ptr = malloc(s);
memset(ptr, 0xFF, s);
return ptr;
}
void operator delete(void* ptr) { free(ptr); }
int value;
};
int main()
{
A* a = new A;
assert(a->value == -1); /* Use of uninitialized value */
delete a;
}
Thanks, I think that would be a much better example for the porting_to
page, since it demonstrates the optimization with fewer lines of code.
