Re: [patch] Avoid #ifdef _GLIBCXX_DEBUG in regex_compiler.h

[Jonathan Wakely]

On 07/09/15 15:54 +0100, Jonathan Wakely wrote:

@@ -457,10 +457,24 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
        return 1ul << (sizeof(_CharT) * __CHAR_BIT__ * int(_UseCache::value));
      }

-      struct _Dummy { };
-      typedef typename std::conditional<_UseCache::value,
-                                       std::bitset<_S_cache_size()>,
-                                       _Dummy>::type _CacheT;
+      struct _Flags
+      {
+       bool _M_is_non_matching;
+       bool _M_is_ready;
+      };
+
+      struct _Empty { };
+
+      struct _ExtraMembers
+      : _Flags,
+       conditional<_UseCache::value, bitset<_S_cache_size()>, _Empty>::type
+      {
+       explicit
+       _ExtraMembers(bool __is_non_matching)
+       : _Flags{__is_non_matching, false}
+       { }
+      };
+

And we could get rid of the _Empty type, because std::bitset<0> is an
empty type anyway, so if we made _S_cache_size()==0 when _UseCache is
false then in the current code we could just unconditionally use:

 using _CacheT = std::bitset<_S_cache_size()>;

and for the suggested change to use a padding byte for the _M_is_ready
flag we could use:

     struct _ExtraMembers
     : _Flags, bitset<_S_cache_size()>
     {
       explicit
       _ExtraMembers(bool __is_non_matching)
       : _Flags{__is_non_matching, false}
       { }
     };