[binutils-gdb/palves/cxx-enum-flags] enum_flags: Use C++11 std::underlying_type

[Pedro Alves <palves at sourceware dot org>]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=de2bb8910a3a46f9af0731449ebb4285cf7ded01

commit de2bb8910a3a46f9af0731449ebb4285cf7ded01
Author: Pedro Alves <palves@redhat.com>
Date:   Thu Nov 3 22:54:35 2016 +0000

    enum_flags: Use C++11 std::underlying_type
    
    Now that we can require C++11, we can use std::underlying_type instead
    of rolling our own.
    
    gdb/ChangeLog:
    yyyy-mm-dd  Pedro Alves  <palves@redhat.com>
    
    	* common/enum-flags.h: Include <type_traits>.
    	(integer_for_size, enum_underlying_type): Delete.
    	(class enum_flags): Use std::underlying_type.

Diff:
---
 gdb/common/enum-flags.h | 24 +++---------------------
 1 file changed, 3 insertions(+), 21 deletions(-)

diff --git a/gdb/common/enum-flags.h b/gdb/common/enum-flags.h
index 9b8c952..ff48067 100644
--- a/gdb/common/enum-flags.h
+++ b/gdb/common/enum-flags.h
@@ -51,6 +51,8 @@
 
 #ifdef __cplusplus
 
+#include <type_traits>
+
 /* Traits type used to prevent the global operator overloads from
    instantiating for non-flag enums.  */
 template<typename T> struct enum_flags_type {};
@@ -66,32 +68,12 @@ template<typename T> struct enum_flags_type {};
     typedef enum_flags<enum_type> type;			\
   }
 
-/* Until we can rely on std::underlying type being universally
-   available (C++11), roll our own for enums.  */
-template<int size, bool sign> class integer_for_size { typedef void type; };
-template<> struct integer_for_size<1, 0> { typedef uint8_t type; };
-template<> struct integer_for_size<2, 0> { typedef uint16_t type; };
-template<> struct integer_for_size<4, 0> { typedef uint32_t type; };
-template<> struct integer_for_size<8, 0> { typedef uint64_t type; };
-template<> struct integer_for_size<1, 1> { typedef int8_t type; };
-template<> struct integer_for_size<2, 1> { typedef int16_t type; };
-template<> struct integer_for_size<4, 1> { typedef int32_t type; };
-template<> struct integer_for_size<8, 1> { typedef int64_t type; };
-
-template<typename T>
-struct enum_underlying_type
-{
-  typedef typename
-    integer_for_size<sizeof (T), static_cast<bool>(T (-1) < T (0))>::type
-    type;
-};
-
 template <typename E>
 class enum_flags
 {
 public:
   typedef E enum_type;
-  typedef typename enum_underlying_type<enum_type>::type underlying_type;
+  typedef typename std::underlying_type<enum_type>::type underlying_type;
 
 private:
   /* Private type used to support initializing flag types with zero: