Re: C++ PATCH for c++/55753 (ICE with constexpr)

[Jason Merrill <jason@redhat.com>]

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And another bug: we were building an AGGR_INIT_EXPR in non-dependent 
code, and then failing to handle it properly in fold_non_dependent_expr. 
  Fixed by not creating AGGR_INIT_EXPR in templates.  As a result, we 
end up with a CALL_EXPR to the address of a constructor, and we need to 
avoid an error when instantiating that by stripping the address and 
letting the call code put it back.

Tested x86_64-pc-linux-gnu, applying to trunk.  This is only an ICE with 
checking enabled, so I'm not going to apply it to 4.7.


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commit 843d522093cdc00181ea4590bf69d5f10162998a
Author: Jason Merrill <jason@redhat.com>
Date:   Mon Jan 7 09:31:13 2013 -0500

    	PR c++/55753
    	* tree.c (build_aggr_init_expr): Do nothing in a template.
    	* pt.c (tsubst_copy_and_build) [CALL_EXPR]: Strip an ADDR_EXPR off
    	a FUNCTION_DECL before tsubsting.

diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 30bafa0..c55dabef 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -13743,6 +13743,11 @@ tsubst_copy_and_build (tree t,
 	    else
 	      qualified_p = false;
 
+	    if (TREE_CODE (function) == ADDR_EXPR
+		&& TREE_CODE (TREE_OPERAND (function, 0)) == FUNCTION_DECL)
+	      /* Avoid error about taking the address of a constructor.  */
+	      function = TREE_OPERAND (function, 0);
+
 	    function = tsubst_copy_and_build (function, args, complain,
 					      in_decl,
 					      !qualified_p,
diff --git a/gcc/cp/tree.c b/gcc/cp/tree.c
index fcab1a4..0824214 100644
--- a/gcc/cp/tree.c
+++ b/gcc/cp/tree.c
@@ -412,6 +412,10 @@ build_aggr_init_expr (tree type, tree init)
   tree rval;
   int is_ctor;
 
+  /* Don't build AGGR_INIT_EXPR in a template.  */
+  if (processing_template_decl)
+    return init;
+
   if (TREE_CODE (init) == CALL_EXPR)
     fn = CALL_EXPR_FN (init);
   else if (TREE_CODE (init) == AGGR_INIT_EXPR)
diff --git a/gcc/testsuite/g++.dg/cpp0x/constexpr-ctor13.C b/gcc/testsuite/g++.dg/cpp0x/constexpr-ctor13.C
new file mode 100644
index 0000000..ed01a31
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/constexpr-ctor13.C
@@ -0,0 +1,15 @@
+// PR c++/55753
+// { dg-options -std=c++11 }
+
+struct A
+{
+  double r,i;
+  constexpr A(double r = 0.0, double i = 0.0): r(r), i(i) {}
+};
+
+template <typename Tp>
+struct B {
+  B() {
+    A((true ? 1.0 : A()));
+  }
+};