C++ PATCH for c++/80077, constexpr and -fno-elide-constructors

Message ID CADzB+2nHrsH-SBHYat2iBsPtm45nbVzXVwSMrwwxYM7m8Zrs1A@mail.gmail.com
State New
Headers show

Commit Message

Jason Merrill March 20, 2017, 2:19 a.m.
My patch to exclude assignments in the actual initializer from being
considered constant-expressions broke this case, where we represent a
trivial copy constructor with a MODIFY_EXPR.  Fixed by indicating that
we are effectively in a call to a constexpr function.

Tested x86_64-pc-linux-gnu, applying to trunk.
commit 8df62c0b0c1c1e57bc5c043231d6bab9e9b5dae0
Author: Jason Merrill <jason@redhat.com>
Date:   Fri Mar 17 14:55:46 2017 -0400

            PR c++/80077 - error with constexpr and -fno-elide-constructors.
    
            * constexpr.c (cxx_eval_call_expression): Set ctx->call while
            expanding trivial constructor.

Patch

diff --git a/gcc/cp/constexpr.c b/gcc/cp/constexpr.c
index 4136b34..3ca3560 100644
--- a/gcc/cp/constexpr.c
+++ b/gcc/cp/constexpr.c
@@ -1478,7 +1478,8 @@  cxx_eval_call_expression (const constexpr_ctx *ctx, tree t,
 	  else
 	    op = build1 (INDIRECT_REF, TREE_TYPE (TREE_TYPE (op)), op);
 	  tree set = build2 (MODIFY_EXPR, TREE_TYPE (op), op, init);
-	  return cxx_eval_constant_expression (ctx, set, lval,
+	  new_ctx.call = &new_call;
+	  return cxx_eval_constant_expression (&new_ctx, set, lval,
 					       non_constant_p, overflow_p);
 	}
     }
@@ -1496,7 +1497,7 @@  cxx_eval_call_expression (const constexpr_ctx *ctx, tree t,
     }
 
   /* If in direct recursive call, optimize definition search.  */
-  if (ctx && ctx->call && ctx->call->fundef->decl == fun)
+  if (ctx && ctx->call && ctx->call->fundef && ctx->call->fundef->decl == fun)
     new_call.fundef = ctx->call->fundef;
   else
     {
diff --git a/gcc/testsuite/g++.dg/cpp0x/constexpr-trivial3.C b/gcc/testsuite/g++.dg/cpp0x/constexpr-trivial3.C
new file mode 100644
index 0000000..6833cd3
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/constexpr-trivial3.C
@@ -0,0 +1,6 @@ 
+// PR c++/80077
+// { dg-do compile { target c++11 } }
+// { dg-options -fno-elide-constructors }
+
+struct X_t { X_t() = default; };
+constexpr X_t x = X_t();