c++: unset COMPOUND_LITERAL_P [PR100079]

Once a CONSTRUCTOR has been digested and used as an initializer, it no
longer represents a compound literal by itself, so we can clear the flag,
letting us use it consistently to distinguish between digested and
undigested initializer-lists.

gcc/cp/ChangeLog:

	* cp-tree.h: Clarify comments.
	* pt.c (get_template_parm_object): Add assert.
	* semantics.c (finish_compound_literal): Clear TREE_HAS_CONSTRUCTOR.
	* tree.c (zero_init_expr_p): Check TREE_HAS_CONSTRUCTOR.
	* typeck2.c (store_init_value): Likewise.

1 files changed, 6 insertions, 2 deletions

diff --git a/gcc/cp/semantics.c b/gcc/cp/semantics.c
index 3a6468f..319a3a8 100644
--- a/gcc/cp/semantics.c
+++ b/gcc/cp/semantics.c
@@ -3177,9 +3177,13 @@ finish_compound_literal (tree type, tree compound_literal,
     }
 
   /* Represent other compound literals with TARGET_EXPR so we produce
-     an lvalue, but can elide copies.  */
+     a prvalue, and can elide copies.  */
   if (!VECTOR_TYPE_P (type))
-    compound_literal = get_target_expr_sfinae (compound_literal, complain);
+    {
+      /* The CONSTRUCTOR is now an initializer, not a compound literal.  */
+      TREE_HAS_CONSTRUCTOR (compound_literal) = false;
+      compound_literal = get_target_expr_sfinae (compound_literal, complain);
+    }
 
   return compound_literal;
 }