Re: C++ PATCH for c++/56567 (ICE with lambda returning init-list)

[Jason Merrill <jason@redhat.com>]

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On 03/08/2013 10:54 AM, Jason Merrill wrote:
> My initial proposal for allowing general return type deduction allowed
> deduction of std::initializer_list, which is not permitted by C++11. But
> this doesn't make sense, because the underlying array will immediately
> leak, so we should just give an error even in C++1y.

As pointed out in the PR, this approach was wrong because it's possible 
to have an expression with std::initializer_list type; the thing 
returned might not have itself been a brace-enclosed init list.  So 
let's catch that earlier.

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



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commit 3d3cc430920cbb17be4e85742c34d51b94537a37
Author: Jason Merrill <jason@redhat.com>
Date:   Mon Mar 11 12:03:31 2013 -0400

    	PR c++/56567
    	* typeck.c (check_return_expr): Disallow returning init list here.
    	* semantics.c (apply_deduced_return_type): Not here.

diff --git a/gcc/cp/semantics.c b/gcc/cp/semantics.c
index 233765a..e909b98 100644
--- a/gcc/cp/semantics.c
+++ b/gcc/cp/semantics.c
@@ -9061,12 +9061,6 @@ apply_deduced_return_type (tree fco, tree return_type)
   if (return_type == error_mark_node)
     return;
 
-  if (is_std_init_list (return_type))
-    {
-      error ("returning %qT", return_type);
-      return_type = void_type_node;
-    }
-
   if (LAMBDA_FUNCTION_P (fco))
     {
       tree lambda = CLASSTYPE_LAMBDA_EXPR (current_class_type);
diff --git a/gcc/cp/typeck.c b/gcc/cp/typeck.c
index 58295d7..58ebcc0 100644
--- a/gcc/cp/typeck.c
+++ b/gcc/cp/typeck.c
@@ -8136,6 +8136,11 @@ check_return_expr (tree retval, bool *no_warning)
 		  "deduced to %<void%>");
 	  type = error_mark_node;
 	}
+      else if (retval && BRACE_ENCLOSED_INITIALIZER_P (retval))
+	{
+	  error ("returning initializer list");
+	  type = error_mark_node;
+	}
       else
 	{
 	  if (!retval)
diff --git a/gcc/testsuite/g++.dg/cpp0x/lambda/lambda-initlist3.C b/gcc/testsuite/g++.dg/cpp0x/lambda/lambda-initlist3.C
index 029287b..f7b82ef 100644
--- a/gcc/testsuite/g++.dg/cpp0x/lambda/lambda-initlist3.C
+++ b/gcc/testsuite/g++.dg/cpp0x/lambda/lambda-initlist3.C
@@ -5,7 +5,7 @@
 
 int main()
 {
-  []{ return { 1, 2 }; }();	// { dg-error "initializer_list" }
+  []{ return { 1, 2 }; }();	// { dg-error "initializer.list" }
 }
 
 // { dg-prune-output "return-statement with a value" }