This fixes an ICE taking place in cp_default_conversion because we got
a SCOPE_REF that doesn't have a type and so checking
INTEGRAL_OR_UNSCOPED_ENUMERATION_TYPE_P (TREE_TYPE (exp)) will crash.
This happens since the recent Joseph's change in decl_attributes whereby
we don't skip C++11 attributes on types.

[dcl.align] is clear that alignas applied to a function is ill-formed.
That should be fixed, and we have PR90847 for that.  But I think a more
appropriate fix at this stage would be the following: in a template we
want to splice dependent attributes and save them for later, and by
doing so avoid this crash.

Bootstrapped/regtested on x86_64-linux, ok for trunk?

        PR c++/93530 - ICE on invalid alignas in a template.
        * decl.c (grokdeclarator): Call cplus_decl_attributes instead of
        decl_attributes.

        * g++.dg/cpp0x/alignas18.C: New test.
---
 gcc/cp/decl.c                          | 2 +-
 gcc/testsuite/g++.dg/cpp0x/alignas18.C | 8 ++++++++
 2 files changed, 9 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/g++.dg/cpp0x/alignas18.C

diff --git a/gcc/cp/decl.c b/gcc/cp/decl.c
index 6ad558eef9e..576cbd8643a 100644
--- a/gcc/cp/decl.c
+++ b/gcc/cp/decl.c
@@ -12300,7 +12300,7 @@ grokdeclarator (const cp_declarator *declarator,
 
                 The optional attribute-specifier-seq appertains to
                 the function type.  */
-             decl_attributes (&type, attrs, 0);
+             cplus_decl_attributes (&type, attrs, 0);
 
            if (raises)
              type = build_exception_variant (type, raises);
diff --git a/gcc/testsuite/g++.dg/cpp0x/alignas18.C 
b/gcc/testsuite/g++.dg/cpp0x/alignas18.C
new file mode 100644
index 00000000000..820bdd2d7ca
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/alignas18.C
@@ -0,0 +1,8 @@
+// PR c++/93530 - ICE on invalid alignas in a template.
+// { dg-do compile { target c++11 } }
+
+template <typename T> struct S {
+  using U = S;
+  // FIXME: This is ill-formed; see PR90847.
+  void fn() alignas(U::X);
+};

base-commit: 2a07345c4f8dabc286fc470e76c53473e5bc3eb7
-- 
Marek Polacek • Red Hat, Inc. • 300 A St, Boston, MA

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