c++: ICE with VEC_INIT_EXPR and defarg [PR106925]

Since r12-8066, in cxx_eval_vec_init we perform expand_vec_init_expr
while processing the default argument in this test.  At this point
start_preparsed_function hasn't yet set current_function_decl.
expand_vec_init_expr then leads to maybe_splice_retval_cleanup which
checks DECL_CONSTRUCTOR_P (current_function_decl) without checking that
c_f_d is non-null first.  It seems correct that c_f_d is null here, so
it seems to me that maybe_splice_retval_cleanup should check c_f_d as
in the following patch.

	PR c++/106925

gcc/cp/ChangeLog:

	* except.cc (maybe_splice_retval_cleanup): Check current_function_decl.
	Make the bool const.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp0x/initlist-defarg3.C: New test.

(cherry picked from commit 3130e70dab1e64a7b014391fe941090d5f3b6b7d)

2 files changed, 18 insertions, 2 deletions

diff --git a/gcc/cp/except.cc b/gcc/cp/except.cc
index da0a65c..58d8772 100644
--- a/gcc/cp/except.cc
+++ b/gcc/cp/except.cc
@@ -1322,9 +1322,12 @@ maybe_splice_retval_cleanup (tree compound_stmt)
 {
   /* If we need a cleanup for the return value, add it in at the same level as
      pushdecl_outermost_localscope.  And also in try blocks.  */
-  bool function_body
+  const bool function_body
     = (current_binding_level->level_chain
-       && current_binding_level->level_chain->kind == sk_function_parms);
+       && current_binding_level->level_chain->kind == sk_function_parms
+      /* When we're processing a default argument, c_f_d may not have been
+	 set.  */
+       && current_function_decl);
 
   if ((function_body || current_binding_level->kind == sk_try)
       && !DECL_CONSTRUCTOR_P (current_function_decl)
diff --git a/gcc/testsuite/g++.dg/cpp0x/initlist-defarg3.C b/gcc/testsuite/g++.dg/cpp0x/initlist-defarg3.C
new file mode 100644
index 0000000..5c3e886
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/initlist-defarg3.C
@@ -0,0 +1,13 @@
+// PR c++/106925
+// { dg-do compile { target c++11 } }
+
+struct Foo;
+template <int _Nm> struct __array_traits { typedef Foo _Type[_Nm]; };
+template <int _Nm> struct array {
+  typename __array_traits<_Nm>::_Type _M_elems;
+};
+template <int size> struct MyVector { array<size> data{}; };
+struct Foo {
+  float a{0};
+};
+void foo(MyVector<1> = MyVector<1>());