On Tue, Jun 28, 2022 at 06:29:01PM +0000, Qing Zhao wrote:
>
>
> > On Jun 28, 2022, at 2:22 PM, Jakub Jelinek <ja...@redhat.com> wrote:
> >
> > On Tue, Jun 28, 2022 at 06:15:58PM +0000, Qing Zhao wrote:
> >>> Because the flag just tells whether some array shouldn't be treated as
> >>> (poor man's)
> >>> flexible array member. We still need to find out if some FIELD_DECL is to
> >>> be treated like a flexible array member, which is a minority of
> >>> COMPONENT_REFs.
> >>> struct S { int a; char b[0]; int c; } s;
> >>> struct T { int d; char e[]; };
> >>> struct U { int f; struct T g; int h; } u;
> >>> Neither s.b nor u.g.e is to be treated like flexible array member,
> >>> no matter what -fstrict-flex-array= option is used.
> >>
> >> Then, to resolve this issue, we might need a opposite flag
> >> DECL_IS_FLEXARRAY in FIELD_DECL?
> >>
> >> The default is FALSE for all FIELD_DECL.
> >
> > Doesn't matter whether it is positive or negative, you still need to analyze
> > it. See the above example. If you have struct T t; and test t.e, then it
> > is flexarray. But u.g.e is not, even when the COMPONENT_REF refers to the
> > same FIELD_DECL. In the t.e case e is the very last field, in the latter
> > case u.g.e is the last field in struct T, but struct U has the h field after
>
> So, do you mean that the current FE analysis will not be able to decide
> whether a specific array field is at the end of the enclosing structure?
> Only the middle end can decide this ?
Well, anything that analyzes it, can be in the FE or middle-end, but there
is no place to store it for later.
Jakub
