kees wrote:
> @kees, the issue should be fixed with the newest push.
Nice! This is so extremely close. It fixed all but 1 instance in the torture
testing. The remaining seems to be union order sensitive. O_o This arrangement
still reports non-zero for the `int count_bytes` one, unless I move it below
the `signed char count_ints` counter:
```
#include <stdint.h>
#include <stdio.h>
#include <string.h>
#include <malloc.h>
#define noinline __attribute__((__noinline__))
#define __counted_by(member) __attribute__((__counted_by__(member)))
#define DECLARE_BOUNDED_FLEX_ARRAY(COUNT_TYPE, COUNT, TYPE, NAME) \
struct { \
COUNT_TYPE COUNT; \
TYPE NAME[] __counted_by(COUNT); \
}
#define DECLARE_FLEX_ARRAY(TYPE, NAME) \
struct { \
struct { } __empty_ ## NAME; \
TYPE NAME[]; \
}
struct multi {
unsigned long flags;
union {
/* count member type intentionally mismatched to induce padding
*/
DECLARE_BOUNDED_FLEX_ARRAY(int, count_bytes, unsigned char,
bytes);
DECLARE_BOUNDED_FLEX_ARRAY(signed char, count_ints, unsigned
char, ints);
DECLARE_FLEX_ARRAY(unsigned char, unsafe);
};
};
/* Helper to hide the allocation size by using a leaf function. */
static struct multi * noinline alloc_multi_ints(int index)
{
struct multi *p;
p = malloc(sizeof(*p) + index * sizeof(*p->ints));
p->count_ints = index;
return p;
}
/* Helper to hide the allocation size by using a leaf function. */
static struct multi * noinline alloc_multi_bytes(int index)
{
struct multi *p;
p = malloc(sizeof(*p) + index * sizeof(*p->bytes));
p->count_bytes = index;
return p;
}
int main(void)
{
struct multi *mi, *mb;
volatile int negative = -3;
volatile int index = 10;
mi = alloc_multi_ints(index);
mi->count_ints = negative;
printf("%zu\n", __builtin_dynamic_object_size(mi->ints, 1));
mb = alloc_multi_bytes(index);
mb->count_bytes = negative;
printf("%zu\n", __builtin_dynamic_object_size(mb->bytes, 1));
return 0;
}
```
Returns:
```
253
0
```
https://github.com/llvm/llvm-project/pull/76348
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