On 2023-10-20 14:38, Qing Zhao wrote:
How about the following:
Add one more parameter to __builtin_dynamic_object_size(), i.e
__builtin_dynamic_object_size (_1,1,array_annotated->foo)?
When we see the structure field has counted_by attribute.
Or maybe add a barrier preventing any assignments to
array_annotated->foo from being reordered below the __bdos call?
Basically an __asm__ with array_annotated->foo in the clobber list ought
to do it I think.
It may not work for something like this though:
static size_t
get_size_of (void *ptr)
{
return __bdos (ptr, 1);
}
void
foo (size_t sz)
{
array_annotated = __builtin_malloc (sz);
array_annotated = sz;
...
__builtin_printf ("%zu\n", get_size_of (array_annotated->foo));
...
}
because the call to get_size_of () may not have been inlined that early.
The more fool-proof alternative may be to put a compile time barrier
right below the assignment to array_annotated->foo; I reckon you could
do that early in the front end by marking the size identifier and then
tracking assignments to that identifier. That may have a slight runtime
performance overhead since it may prevent even legitimate reordering. I
can't think of another alternative at the moment...
Sid
