Re: [V2][PATCH 0/3] New attribute "counted_by" to annotate bounds for C99 FAM(PR108896)

[Qing Zhao via Gcc-patches]

> On Aug 10, 2023, at 12:39 PM, Jakub Jelinek <ja...@redhat.com> wrote:
> 
> On Thu, Aug 10, 2023 at 12:30:06PM -0400, Siddhesh Poyarekar wrote:
>> The definition of __bos/__bdos allows us the freedom to *estimate* rather
>> than be precise, so I'd go for sizeof(x) + N * sizeof(*x.a) since it's bound
>> to give the more conservative answer of the two.
> 
> To be precise, we have the 0/1 modes vs. 2/3.  So, when not determining
> __bos/__bdos from actual allocation size or size of an stack object or
> size of data section object but something else (say counted_by), perhaps
> 0/1 modes should give the upper estimate of sizeof (x) + N * sizeof(elt)
> and 2/3 modes should give a lower estimate, so offsetof + N * sizeof(elt),
> then user code can continue testing if both modes are equal to have
> exact number.

Yes, this sounds reasonable to me.

Qing
> 
>       Jakub
>