> On Dec 3, 2025, at 01:55, Martin Uecker <[email protected]> wrote:
>
>
> If we already had a pointer-version, i.e.
>
> struct __bounded_ptr {
> int k;
> [[gnu::counted_by(k) int *buf;
> };
>
> one could also rewrite the call to 'f1' to
>
> int *p = f1 (3);
> (struct __bound_ptr){ 3, f1(3) }.buf
Thanks a lot for this idea.
I tried to modify the current small testing case with the above as the
following:
int* f (int);
struct __bounded_ptr {
int k;
int *buf __attribute__ ((counted_by (k)));
};
int*
f1 (int n) { return f (n); }
void h1 (void)
{
int *p = (struct __bounded_ptr) {3, f1 (3)}.buf;
__builtin_memset (p, 0, 3 * sizeof p); // missing warning
}
And tried to compile with the latest gcc, however, got an ICE at gimplify_expr:
t1.c: In function ‘h1’:
t1.c:13:12: internal compiler error: in gimplify_expr, at gimplify.cc:21136
13 | int *p = (struct __bounded_ptr) {3, f1 (3)}.buf;
| ^
0x2279fbb internal_error(char const*, ...)
../../latest-gcc-write/gcc/diagnostic-global-context.cc:534
0x843137 fancy_abort(char const*, int, char const*)
Delete the counted_by attribute, the ICE is gone. So I guess that this is a bug
in
the current handling of counted_by for pointers.
I will try to study and fix this bug first, and then re-start from there.
Thanks a lot.
Qing
>
> and then the compound ref logic would do the right thing.
>
>
> Martin
>
>
> Am Mittwoch, dem 03.12.2025 um 07:43 +0100 schrieb Martin Uecker:
>> Am Dienstag, dem 02.12.2025 um 21:21 +0000 schrieb Qing Zhao:
>>>
>>>> On Dec 2, 2025, at 15:56, Martin Uecker <[email protected]> wrote:
>>>>
>>>>
>>>> Hi Qing,
>>>>
>>>> Am Dienstag, dem 02.12.2025 um 20:33 +0000 schrieb Qing Zhao:
>>>>> Hi, Joseph and Martin:
>>>>>
>>>>> I am now working on PR96503 (attribute alloc_size effect lost after
>>>>> inlining)
>>>>> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96503
>>>>>
>>>>> My first major questions are:
>>>>>
>>>>> for the simple case in the PR:
>>>>>
>>>>> __attribute__ ((alloc_size (1))) int* f1 (int n) { return f (n); }
>>>>>
>>>>> void h1 (void)
>>>>> {
>>>>> int *p = f1 (3);
>>>>> __builtin_memset (p, 0, 3 * sizeof p); // missing warning
>>>>> }
>>>>>
>>>>> 1. where in the IR we should insert the call to the internal function
>>>>> .ACCESS_WITH_SIZE?
>>>>>
>>>>> My basic idea is: when the call to a routine marked with "alloc_size"
>>>>> attribute, generate a call to .ACCESS_WITH_SIZE for its assigned returned
>>>>> pointer.
>>>>>
>>>>> i.e, in the above example, when we see
>>>>>
>>>>> p = f1 (3)
>>>>>
>>>>> we will wrap the pointer "p" with .ACCESS_WITH_SIZE (p, 3, 0, 1), i.e,
>>>>> .ACCESS_WITH_SIZE (p, 3, 0, 1) = f1 (3);
>>>>>
>>>>> is this reasonable?
>>>>
>>>> My guess would be that this should be
>>>>
>>>> p = .ACCESS_WITH_SIZE(f1(3), 3, 0, 1);
>>>
>>> Our current design of .ACCESS_WITH_SIZE is:
>>>
>>> ACCESS_WITH_SIZE (REF_TO_OBJ, REF_TO_SIZE,
>>> TYPE_OF_SIZE + ACCESS_MODE, TYPE_SIZE_UNIT for element)
>>> which returns the REF_TO_OBJ same as the 1st argument;
>>>
>>> Therefore, the first argument of the routine “.ACCESS_WITH_SIZE” is the
>>> REF_TO_OBJ itself.
>>
>> How is the .ACCESS_WITH_SIZE discovered by BDOS
>> when you do the following?
>>
>> .ACCESS_WITH_SIZE (p, 3, 0, 1) = f1 (3);
>> use(p); // will BDOS find the information?
>>
>> It isn't clear to me how this would work.
>>
>> And isn't the object we are talking about the pointed-to array,
>> so p would already be the ref itself.
>>
>>>
>>> For the “alloc_size” attribute, we can consider it as an “counted_by”
>>> attribute added
>>> to the “returned pointer” of the function call.
>>
>> Now the counted_by is attached to the FAM and we pass a
>> pointer to the FAM, so for me it seems we would need to pass
>> the pointer to the object we want to bound.
>>
>> For size we can create a temporary object, or we need another
>> version of .ACCESS_WITH_SIZE.
>>
>> Martin
>>
>>
>>> So, adding the attribute to the pointer that is assigned by the returned
>>> value of the
>>> function is a reasonable approximation from my pointer of view.
>>>
>>> What do you think?
>>
>>
>>
>>
>>>
>>>>
>>>> or am I missing something?
>>>>
>>>>>
>>>>> 2. If the above idea is reasonable, where should I implement this in C FE?
>>>>>
>>>>> What’s in my mind is: where a function returned value is assigned to a
>>>>> pointer,
>>>>> checking whether the function type has “alloc_size” attribute, if so,
>>>>> wrapping
>>>>> The pointer that the function assigned to to a call to .ACCESS_WITH_SIZE.
>>>>>
>>>>> Which parts of the code, or which routines in C FE I should focus on?
>>>>
>>>> build_function_call_vec ?
>>> Thanks, will take a look at it.
>>>
>>> Qing
>>>>
>>>>>
>>>>> Let me know if you have any comments and suggestions.
>>>>
>>>>
>>>> Martin
>>>>
>>>>>
>>>>> Thanks a lot for your help.
>>>
