Patchwork C++ PATCH to disable -fdeduce-init-list by default

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Submitter Jason Merrill
Date Nov. 1, 2011, 4:02 a.m.
Message ID <4EAF6F4B.3090105@redhat.com>
Download mbox | patch
Permalink /patch/123017/
State New
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Comments

Jason Merrill - Nov. 1, 2011, 4:02 a.m.
In my implementation of the C++11 list-initialization proposal, I also 
implemented an extension that allowed for deduction of 
std::initializer_list<...> for a template type parameter, so that people 
could try it out and see what they thought.  This extension didn't make 
it into C++11, so I'm switching its flag to be off by default.

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

Patch

commit 03e84320fcb7868a31016c7cb80596e38a5183d5
Author: Jason Merrill <jason@redhat.com>
Date:   Mon Oct 31 22:02:29 2011 -0400

    	* c.opt (-fdeduce-init-list): Off by default.

diff --git a/gcc/c-family/c.opt b/gcc/c-family/c.opt
index 336a75a..6d50097 100644
--- a/gcc/c-family/c.opt
+++ b/gcc/c-family/c.opt
@@ -752,8 +752,8 @@  C ObjC C++ ObjC++
 Emit debug annotations during preprocessing
 
 fdeduce-init-list
-C++ ObjC++ Var(flag_deduce_init_list) Init(1)
--fno-deduce-init-list	disable deduction of std::initializer_list for a template type parameter from a brace-enclosed initializer-list
+C++ ObjC++ Var(flag_deduce_init_list) Init(0)
+-fdeduce-init-list	enable deduction of std::initializer_list for a template type parameter from a brace-enclosed initializer-list
 
 fdefault-inline
 C++ ObjC++ Ignore
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 0c97453..2836b74 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -1907,9 +1907,9 @@  to @var{n}.  A limit is needed to detect endless recursion during
 constant expression evaluation.  The minimum specified by the standard
 is 512.
 
-@item -fno-deduce-init-list
-@opindex fno-deduce-init-list
-Disable deduction of a template type parameter as
+@item -fdeduce-init-list
+@opindex fdeduce-init-list
+Enable deduction of a template type parameter as
 std::initializer_list from a brace-enclosed initializer list, i.e.
 
 @smallexample
@@ -1924,9 +1924,10 @@  void f()
 @}
 @end smallexample
 
-This option is present because this deduction is an extension to the
-current specification in the C++0x working draft, and there was
-some concern about potential overload resolution problems.
+This deduction was implemented as a possible extension to the
+originally proposed semantics for the C++11 standard, but was not part
+of the final standard, so it is disabled by default.  This option is
+deprecated, and may be removed in a future version of G++.
 
 @item -ffriend-injection
 @opindex ffriend-injection
diff --git a/gcc/testsuite/g++.dg/cpp0x/initlist-deduce.C b/gcc/testsuite/g++.dg/cpp0x/initlist-deduce.C
index e422132..373044f 100644
--- a/gcc/testsuite/g++.dg/cpp0x/initlist-deduce.C
+++ b/gcc/testsuite/g++.dg/cpp0x/initlist-deduce.C
@@ -2,7 +2,7 @@ 
 // supported by the working draft, but is necessary for perfect forwarding
 // of initializer-lists to things that can take a std::initializer_list.
 
-// { dg-options -std=c++0x }
+// { dg-options "-std=c++0x -fdeduce-init-list" }
 // { dg-do run }
 
 #include <initializer_list>