> 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.
For the “alloc_size” attribute, we can consider it as an “counted_by” attribute
added
to the “returned pointer” of the function call.
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.
