On Thu, Mar 09, 2017 at 12:00:48AM +0100, Marek Polacek wrote:
> We crash on an assert in strip_typedefs, because we find ourselves in a
> scenario where RESULT, the main variant of a struct, was modified in
> finalize_record_size (its TYPE_ALIGN changed), but its variants (T in
> strip_typedefs) weren't fixed-up yet; that will happen slightly later in
> finalize_type_size. So there's a discrepancy that confuses the code.
>
> This patch implements what Jason suggested to me on IRC, i.e., skip the
> attribute handling if RESULT is complete and T isn't.
>
> Bootstrapped/regtested on x86_64-linux, ok for trunk?
>
> 2017-03-08 Marek Polacek <pola...@redhat.com>
>
> PR c++/79900 - ICE in strip_typedefs
> * tree.c (strip_typedefs): Skip the attribute handling if T is
> a variant type which hasn't been updated yet.
>
> * g++.dg/warn/Wpadded-1.C: New test.
>
> diff --git gcc/testsuite/g++.dg/warn/Wpadded-1.C
> gcc/testsuite/g++.dg/warn/Wpadded-1.C
> index e69de29..b3f0581 100644
> --- gcc/testsuite/g++.dg/warn/Wpadded-1.C
> +++ gcc/testsuite/g++.dg/warn/Wpadded-1.C
> @@ -0,0 +1,22 @@
> +// PR c++/79900 - ICE in strip_typedefs
> +// { dg-do compile }
> +// { dg-options "-Wpadded" }
> +
> +template <class> struct A;
> +template <typename> struct B { // { dg-warning "padding struct size to
> alignment boundary" }
> + long _M_off;
> + int _M_state;
> +};
This fails on i686-linux, there is obviously no padding of struct size to
alignment boundary in that case.
Can't _M_state be e.g. char, then it would work at least on all targets
where long has alignment of at least 2 (that can be all of them)?
Perhaps also make _M_off long long or add a double or long double field.
> +template <> struct A<char> { typedef B<int> pos_type; };
> +enum _Ios_Openmode {};
> +struct C {
> + typedef _Ios_Openmode openmode;
> +};
> +template <typename, typename _Traits> struct D {
> + typedef typename _Traits::pos_type pos_type;
> + pos_type m_fn1(pos_type, C::openmode);
> +};
> +template class D<char, A<char> >;
> +template <typename _CharT, typename _Traits>
> +typename D<_CharT, _Traits>::pos_type D<_CharT, _Traits>::m_fn1(pos_type x,
> + C::openmode)
> { return x; }
Jakub
