On Fri, 24 Feb 2023 at 11:52, Jakub Jelinek <ja...@redhat.com> wrote:
>
> On Fri, Feb 24, 2023 at 12:44:44PM +0100, Richard Biener wrote:
> > --- a/gcc/vec.h
> > +++ b/gcc/vec.h
> > @@ -586,8 +586,8 @@ public:
> > unsigned allocated (void) const { return m_vecpfx.m_alloc; }
> > unsigned length (void) const { return m_vecpfx.m_num; }
> > bool is_empty (void) const { return m_vecpfx.m_num == 0; }
> > - T *address (void) { return m_vecdata; }
> > - const T *address (void) const { return m_vecdata; }
> > + T *address (void) { return reinterpret_cast <T *> (this + 1); }
> > + const T *address (void) const { return reinterpret_cast <const T *>
> > (this + 1); }
>
> This is now too long.
>
> > T *begin () { return address (); }
> > const T *begin () const { return address (); }
> > T *end () { return address () + length (); }
> > @@ -631,8 +631,7 @@ public:
> >
> > /* FIXME - These fields should be private, but we need to cater to
> > compilers that have stricter notions of PODness for types. */
> > - vec_prefix m_vecpfx;
> > - T m_vecdata[1];
> > + alignas (T) vec_prefix m_vecpfx;
>
> The comment needs adjustment and down't we need
> alignas (T) alignas (vec_prefix) ?
Yes. If alignas(T) is less than the natural alignment then this will
be an error. We want it to be the larger of the two alignments, so we
need to specify both.
>
> > @@ -1588,7 +1587,7 @@ public:
> >
> > private:
> > vec<T, va_heap, vl_embed> m_auto;
> > - T m_data[MAX (N - 1, 1)];
> > + alignas(T) unsigned char m_data[sizeof (T) * N];
> > };
>
> I still believe you don't need alignas(T) here (and space before (T) ).
> Also, I think it needs to be MAX (N, 2) instead of N, because auto_vec
> ctors use MAX (N, 2). We could also change all those to MAX (N, 1)
> now, but it can't be N because m_data[sizeof (T) * 0] is invalid in
> standard C.
>
> Anyway, I wonder if you get the -Werror=stringop-overflow= errors during
> bootstrap that I got with my version or not.
>
> Jakub
>
