diff mbox series

[pushed] c++: empty base constexpr -fno-elide-ctors [PR105245]

Message ID 20220413141812.3181344-1-jason@redhat.com
State Committed
Commit ec03862f809e544a9b7d28067e51597dc92a0244
Headers
Series [pushed] c++: empty base constexpr -fno-elide-ctors [PR105245] |

Commit Message

Jason Merrill April 13, 2022, 2:18 p.m. UTC 
  The patch for 100111 extended our handling of empty base elision to the case
where the derived class has no other fields, but we still need to make sure
that there's some initializer for the derived object.

Tested x86_64-pc-linux-gnu, applying to trunk.

	PR c++/105245
	PR c++/100111

gcc/cp/ChangeLog:

	* constexpr.cc (cxx_eval_store_expression): Build a CONSTRUCTOR
	as needed in empty base handling.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp1y/constexpr-empty2.C: Add -fno-elide-constructors.
---
 gcc/cp/constexpr.cc                           | 6 ++++++
 gcc/testsuite/g++.dg/cpp1y/constexpr-empty2.C | 1 +
 2 files changed, 7 insertions(+)


base-commit: 31350635bfd90beea79b0e9220008da12bbb5d22
diff mbox series

Patch

diff --git a/gcc/cp/constexpr.cc b/gcc/cp/constexpr.cc
index 1ce1842430d..b170053e8e1 100644
--- a/gcc/cp/constexpr.cc
+++ b/gcc/cp/constexpr.cc
@@ -5933,6 +5933,12 @@  cxx_eval_store_expression (const constexpr_ctx *ctx, tree t,
     {
       /* See above on initialization of empty bases.  */
       gcc_assert (is_empty_class (TREE_TYPE (init)) && !lval);
+      if (!*valp)
+	{
+	  /* But do make sure we have something in *valp.  */
+	  *valp = build_constructor (type, nullptr);
+	  CONSTRUCTOR_NO_CLEARING (*valp) = no_zero_init;
+	}
       return init;
     }
   else
diff --git a/gcc/testsuite/g++.dg/cpp1y/constexpr-empty2.C b/gcc/testsuite/g++.dg/cpp1y/constexpr-empty2.C
index 2acfa98364b..9768b89904e 100644
--- a/gcc/testsuite/g++.dg/cpp1y/constexpr-empty2.C
+++ b/gcc/testsuite/g++.dg/cpp1y/constexpr-empty2.C
@@ -1,4 +1,5 @@ 
 // { dg-do compile { target c++14 } }
+// { dg-additional-options -fno-elide-constructors }
 
 struct A
 {