On 5/24/22 09:55, Marek Polacek wrote:
On Tue, May 24, 2022 at 08:36:39AM -0400, Jason Merrill wrote:
On 5/16/22 11:36, Marek Polacek wrote:
+static tree
+replace_placeholders_for_class_temp_r (tree *tp, int *, void *data)
+{
+  tree t = *tp;
+  tree full_expr = *static_cast<tree *>(data);
+
+  /* We're looking for a TARGET_EXPR nested in the whole expression.  */
+  if (TREE_CODE (t) == TARGET_EXPR
+      && !potential_prvalue_result_of (t, full_expr))
+    {
+      tree init = TARGET_EXPR_INITIAL (t);
+      while (TREE_CODE (init) == COMPOUND_EXPR)
+       init = TREE_OPERAND (init, 1);

Hmm, how do we get a COMPOUND_EXPR around a CONSTRUCTOR?

Sadly, that's possible for code like (from nsdmi-aggr18.C)

struct D {
   int x = 42;
   B b = (true, A{x});
};

where the TARGET_EXPR_INITIAL is
<<< Unknown tree: void_cst >>>, {.x=((struct D *) this)->x, .y=(&<PLACEHOLDER_EXPR 
struct A>)->x}

Hmm, perhaps cp_build_compound_expr should build an additional TARGET_EXPR around the COMPOUND_EXPR but leave the one inside alone. Feel free to investigate that if you'd like, or the patch is OK as is.

Jason

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