c++: ICE with reference NSDMI [PR114854]

Here we crash on a cp_gimplify_expr/TARGET_EXPR assert:

      /* A TARGET_EXPR that expresses direct-initialization should have been
         elided by cp_gimplify_init_expr.  */
      gcc_checking_assert (!TARGET_EXPR_DIRECT_INIT_P (*expr_p));

the TARGET_EXPR in question is created for the NSDMI in:

  class Vector { int m_size; };
  struct S {
    const Vector &vec{};
  };

where we first need to create a Vector{} temporary, and then bind the
vec reference to it.  The temporary is represented by a TARGET_EXPR
and it cannot be elided.  When we create an object of type S, we get

  D.2848 = {.vec=(const struct Vector &) &TARGET_EXPR <D.2840, {.m_size=0}>}

where the TARGET_EXPR is no longer direct-initializing anything.

Fixed by not setting TARGET_EXPR_DIRECT_INIT_P in convert_like_internal/ck_user.

	PR c++/114854

gcc/cp/ChangeLog:

	* call.cc (convert_like_internal) <case ck_user>: Don't set
	TARGET_EXPR_DIRECT_INIT_P.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp1y/nsdmi-aggr22.C: New test.

diff --git a/gcc/cp/call.cc b/gcc/cp/call.cc
index e058da7735fadb0732d174e5a8ea8e7edff98b72..ed68eb3c568418e4a17f16294e75d1ba363ef4c1 100644 (file)
--- a/gcc/cp/call.cc
+++ b/gcc/cp/call.cc
@@ -8597,16 +8597,12 @@ convert_like_internal (conversion *convs, tree expr, tree fn, int argnum,
            && TYPE_HAS_DEFAULT_CONSTRUCTOR (totype)
            && !processing_template_decl)
          {
-           bool direct = CONSTRUCTOR_IS_DIRECT_INIT (expr);
            if (abstract_virtuals_error (NULL_TREE, totype, complain))
              return error_mark_node;
            expr = build_value_init (totype, complain);
            expr = get_target_expr (expr, complain);
            if (expr != error_mark_node)
-             {
-               TARGET_EXPR_LIST_INIT_P (expr) = true;
-               TARGET_EXPR_DIRECT_INIT_P (expr) = direct;
-             }
+             TARGET_EXPR_LIST_INIT_P (expr) = true;
            return expr;
          }
 

diff --git a/gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr22.C b/gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr22.C
new file mode 100644 (file)
index 0000000..a4f9ae1
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1y/nsdmi-aggr22.C
@@ -0,0 +1,12 @@
+// PR c++/114854
+// { dg-do compile { target c++14 } }
+
+struct Vector {
+  int m_size;
+};
+struct S {
+  const Vector &vec{};
+};
+
+void spawn(S);
+void test() { spawn({}); }