On Wed, 8 Feb 2023, Qing Zhao wrote:

> 
> 
> > On Feb 7, 2023, at 6:37 PM, Joseph Myers <joseph@codesourcery.com> wrote:
> > 
> > On Tue, 7 Feb 2023, Qing Zhao via Gcc-patches wrote:
> > 
> >> Then, this routine (flexible_array_type_p) is mainly for diagnostic purpose.
> >> It cannot be used to determine whether the structure/union type recursively
> >> include a flexible array member at the end.
> >> 
> >> Is my understanding correct?
> > 
> > My comments were about basic principles of what gets diagnosed, and the 
> > need for different predicates in different contexts; I wasn't trying to 
> > assert anything about how that maps onto what functions should be used in 
> > what contexts.
> Okay. 
> 
> But I noticed that “flexible_array_type_p” later was moved from FE to
>  middle-end and put into tree.cc, tree.h as a general utility routine, and to 
> 
> /* Determine whether TYPE is a structure with a flexible array member,
>    or a union containing such a structure (possibly recursively).  */
> 
> However, since this routine does not cover the cases when the structure 
> with flexible array member was recursively embedded into structures, (which we 
> agreed that it should be considered as a flexible sized type). 
> 
> Therefore, I feel that It might not be proper to include this routine in middle end 
> (and actually no other places In middle end use this routine so far).
> 
> That’s the reason I asked the previous question. 
> 
> It might be better to move the routine “flexible_array_type_p” back from middle-end to
> FE for the diagnosis purpose only. 

It's always dangerous to move functions with such a descriptive name to
a place where it suggests wider use is applicable.  Also since
objc/objc-act.cc has a function with the same name (if that had same
content before r10-5097-g4569f8b3652ae1 then the function should
have been moved to c-family/ instead).

The only "middle-end" use, btw., is in ./config/nios2/nios2.cc,
intoduced by said revision and your points probably mean this change
was misguided and flexible_array_type_p isn't the thing to fix here.
flexible-size _objects_ are clearly denoted by DECL_SIZE being
non-constant - though the case of .sdata is quite odd and the issue
fixed is probably running into a bug elsewhere ...

Sandra?

Thanks,
Richard.