OK.
On Wed, Mar 8, 2017 at 6:00 PM, Marek Polacek <pola...@redhat.com> 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/cp/tree.c gcc/cp/tree.c
> index d3c63b8..b3a4a10 100644
> --- gcc/cp/tree.c
> +++ gcc/cp/tree.c
> @@ -1548,29 +1548,40 @@ strip_typedefs (tree t, bool *remove_attributes)
> result = TYPE_MAIN_VARIANT (t);
> }
> gcc_assert (!typedef_variant_p (result));
> - if (TYPE_USER_ALIGN (t) != TYPE_USER_ALIGN (result)
> - || TYPE_ALIGN (t) != TYPE_ALIGN (result))
> +
> + if (COMPLETE_TYPE_P (result) && !COMPLETE_TYPE_P (t))
> + /* If RESULT is complete and T isn't, it's likely the case that T
> + is a variant of RESULT which hasn't been updated yet. Skip the
> + attribute handling. */;
> + else
> {
> - gcc_assert (TYPE_USER_ALIGN (t));
> - if (remove_attributes)
> - *remove_attributes = true;
> - else
> + if (TYPE_USER_ALIGN (t) != TYPE_USER_ALIGN (result)
> + || TYPE_ALIGN (t) != TYPE_ALIGN (result))
> {
> - if (TYPE_ALIGN (t) == TYPE_ALIGN (result))
> - result = build_variant_type_copy (result);
> + gcc_assert (TYPE_USER_ALIGN (t));
> + if (remove_attributes)
> + *remove_attributes = true;
> else
> - result = build_aligned_type (result, TYPE_ALIGN (t));
> - TYPE_USER_ALIGN (result) = true;
> + {
> + if (TYPE_ALIGN (t) == TYPE_ALIGN (result))
> + result = build_variant_type_copy (result);
> + else
> + result = build_aligned_type (result, TYPE_ALIGN (t));
> + TYPE_USER_ALIGN (result) = true;
> + }
> + }
> +
> + if (TYPE_ATTRIBUTES (t))
> + {
> + if (remove_attributes)
> + result = apply_identity_attributes (result, TYPE_ATTRIBUTES (t),
> + remove_attributes);
> + else
> + result = cp_build_type_attribute_variant (result,
> + TYPE_ATTRIBUTES (t));
> }
> }
> - if (TYPE_ATTRIBUTES (t))
> - {
> - if (remove_attributes)
> - result = apply_identity_attributes (result, TYPE_ATTRIBUTES (t),
> - remove_attributes);
> - else
> - result = cp_build_type_attribute_variant (result, TYPE_ATTRIBUTES
> (t));
> - }
> +
> return cp_build_qualified_type (result, cp_type_quals (t));
> }
>
> 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;
> +};
> +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; }
>
> Marek
