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C++ PATCH for c++/50473 (constexpr and static reference members)

Message ID 546A57C2.606@redhat.com
State New
Headers show

Commit Message

Jason Merrill Nov. 17, 2014, 8:17 p.m. UTC 
Trying to establish a constant value for an uninstantiated constexpr 
reference is complicated because of temporary binding semantics.  Best 
to just treat it as value-dependent.

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

commit 23fbd2ea665ffbc88722f918d8acc44c70614fc0
Author: Jason Merrill <jason@redhat.com>
Date:   Sun Nov 16 23:35:27 2014 -0500

    	PR c++/50473
    	* decl.c (cp_finish_decl): Don't try to process a non-dependent
    	constant initializer for a reference.
    	* pt.c (value_dependent_expression_p): A reference is always
    	dependent.
    	* call.c (extend_ref_init_temps_1): Also clear TREE_SIDE_EFFECTS
    	on any NOP_EXPRs.

diff --git a/gcc/cp/call.c b/gcc/cp/call.c
index 4f0b172..06162aa 100644
--- a/gcc/cp/call.c
+++ b/gcc/cp/call.c
@@ -9712,9 +9712,11 @@  extend_ref_init_temps_1 (tree decl, tree init, vec<tree, va_gc> **cleanups)
     {
       tree subinit = NULL_TREE;
       *p = set_up_extended_ref_temp (decl, *p, cleanups, &subinit);
+      recompute_tree_invariant_for_addr_expr (sub);
+      if (init != sub)
+	init = fold_convert (TREE_TYPE (init), sub);
       if (subinit)
 	init = build2 (COMPOUND_EXPR, TREE_TYPE (init), subinit, init);
-      recompute_tree_invariant_for_addr_expr (sub);
     }
   return init;
 }
diff --git a/gcc/cp/decl.c b/gcc/cp/decl.c
index 47da0ca..e69b521 100644
--- a/gcc/cp/decl.c
+++ b/gcc/cp/decl.c
@@ -6419,6 +6419,7 @@  cp_finish_decl (tree decl, tree init, bool init_const_expr_p,
       else if (init
 	       && init_const_expr_p
 	       && !type_dependent_p
+	       && TREE_CODE (type) != REFERENCE_TYPE
 	       && decl_maybe_constant_var_p (decl)
 	       && !type_dependent_init_p (init)
 	       && !value_dependent_init_p (init))
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 1ee3dc1..c0f3b8c 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -20959,6 +20959,8 @@  value_dependent_expression_p (tree expression)
       if (DECL_INITIAL (expression)
 	  && decl_constant_var_p (expression)
 	  && (TREE_CODE (DECL_INITIAL (expression)) == TREE_LIST
+	      /* cp_finish_decl doesn't fold reference initializers.  */
+	      || TREE_CODE (TREE_TYPE (expression)) == REFERENCE_TYPE
 	      || value_dependent_expression_p (DECL_INITIAL (expression))))
 	return true;
       return false;
diff --git a/gcc/testsuite/g++.dg/cpp0x/constexpr-ice12.C b/gcc/testsuite/g++.dg/cpp0x/constexpr-ice12.C
index 98f53b1..c548337 100644
--- a/gcc/testsuite/g++.dg/cpp0x/constexpr-ice12.C
+++ b/gcc/testsuite/g++.dg/cpp0x/constexpr-ice12.C
@@ -3,7 +3,7 @@ 
 
 struct A
 {
-  static constexpr int&& i = 0;  // { dg-error "initialization" }
+  static constexpr int&& i = 0;
 };
 
 int j = A::i;
diff --git a/gcc/testsuite/g++.dg/cpp0x/constexpr-ref5.C b/gcc/testsuite/g++.dg/cpp0x/constexpr-ref5.C
new file mode 100644
index 0000000..230510c
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/constexpr-ref5.C
@@ -0,0 +1,13 @@ 
+// PR c++/50473
+// { dg-do compile { target c++11 } }
+
+constexpr int f() { return 1; }
+
+template<class T>
+struct test
+{
+  static constexpr const auto& value = f();
+  int a[value];
+};
+
+test<int> t;