[gcc r13-3277] c++: ICE with VEC_INIT_EXPR and defarg [PR106925]

[Marek Polacek <mpolacek@gcc.gnu.org>]

https://gcc.gnu.org/g:3130e70dab1e64a7b014391fe941090d5f3b6b7d

commit r13-3277-g3130e70dab1e64a7b014391fe941090d5f3b6b7d
Author: Marek Polacek <polacek@redhat.com>
Date:   Tue Oct 11 14:16:54 2022 -0400

    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.

Diff:
---
 gcc/cp/except.cc                              |  7 +++++--
 gcc/testsuite/g++.dg/cpp0x/initlist-defarg3.C | 13 +++++++++++++
 2 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/gcc/cp/except.cc b/gcc/cp/except.cc
index 703d1d566c9..2677a9b7678 100644
--- a/gcc/cp/except.cc
+++ b/gcc/cp/except.cc
@@ -1307,9 +1307,12 @@ 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 00000000000..5c3e886b306
--- /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>());