> On Jun 28, 2022, at 2:49 PM, Jakub Jelinek <ja...@redhat.com> wrote: > > 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.
Then I am a little confused: If the FE can decide wether an array field is at the end of the enclosing structure, then combined with whether it’s a [0], [1] or [], and which level of -fstrict-flex-array, The FE should be able to decide whether this array field is a flexible array member or not, then set the flag DECL_IS_FLEXARRAY (or DECL_NOT_FLEXARRAY). The new flag is the place to store such info, right? Do I miss anything here? Qing > > Jakub