[gcc r12-2653] c++: ICE on anon struct with base [PR96636]

[Jason Merrill <jason@gcc.gnu.org>]

https://gcc.gnu.org/g:af76342b444948ab262b276cdf083c2d2e0cebbb

commit r12-2653-gaf76342b444948ab262b276cdf083c2d2e0cebbb
Author: Jason Merrill <jason@redhat.com>
Date:   Fri Jul 30 16:49:03 2021 -0400

    c++: ICE on anon struct with base [PR96636]
    
    pinski pointed out that my recent change to reject anonymous structs with
    bases was relevant to this PR.  But we still ICEd after giving that error;
    this fixes the ICE.
    
            PR c++/96636
    
    gcc/cp/ChangeLog:
    
            * decl.c (fixup_anonymous_aggr): Clear TYPE_NEEDS_CONSTRUCTING
            after error.
    
    gcc/testsuite/ChangeLog:
    
            * g++.dg/ext/anon-struct9.C: New test.

Diff:
---
 gcc/cp/decl.c                           | 6 +++++-
 gcc/testsuite/g++.dg/ext/anon-struct9.C | 9 +++++++++
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/gcc/cp/decl.c b/gcc/cp/decl.c
index e4be6be1819..6fa6b9adc87 100644
--- a/gcc/cp/decl.c
+++ b/gcc/cp/decl.c
@@ -5094,7 +5094,11 @@ fixup_anonymous_aggr (tree t)
       tree field, type;
 
       if (BINFO_N_BASE_BINFOS (TYPE_BINFO (t)))
-	error_at (location_of (t), "anonymous struct with base classes");
+	{
+	  error_at (location_of (t), "anonymous struct with base classes");
+	  /* Avoid ICE after error on anon-struct9.C.  */
+	  TYPE_NEEDS_CONSTRUCTING (t) = false;
+	}
 
       for (field = TYPE_FIELDS (t); field; field = DECL_CHAIN (field))
 	if (TREE_CODE (field) == FIELD_DECL)
diff --git a/gcc/testsuite/g++.dg/ext/anon-struct9.C b/gcc/testsuite/g++.dg/ext/anon-struct9.C
new file mode 100644
index 00000000000..56759429620
--- /dev/null
+++ b/gcc/testsuite/g++.dg/ext/anon-struct9.C
@@ -0,0 +1,9 @@
+// PR c++/96636
+// { dg-options "" }
+
+typedef class {
+  class a {};
+  class : virtual a {};		// { dg-error "anonymous struct with base" }
+} b;
+void foo(){ b();}
+