Re: (non)Use of C++ 11 constructs in skeleton

Hi Don,

> Le 19 mai 2019 à 10:12, Akim Demaille <[email protected]> a écrit :
> 
> Hi Don,
> 
>> Le 19 mai 2019 à 04:02, Don Macpherson <[email protected]> a écrit :
>> 
>> Hi,
>> Various places in the C++ skeleton have comments of the form:
>> 
>> /// This class is not copyable
>> /// Prohibit blind copies
>> 
>> while not actually informing the compiler of this fact (though the use of =
>> delete).
>> 
>> Given that the skeleton already has other C++11 conditional code, and that
>> the code produced by the skeleton is consumed within the users code base,
>> the output from the skeleton should endeavour to appropriately use other
>> modern C++ features.
> 
> Yes, you are right, we should also do that.  So far I resisted the temptation to keep the out simple and avoid cascades of #if, but maybe we should do it anyway.
> 
> Bison 3.4 is about to be published, I'm not going to do that now, but we'll do that afterwards.

Well, we are one year later, in exactly the same situation, since 3.6 is
about to be released.

But let's do it.

Cheers!

commit 5b4725d85a38beeeded4800d91829e7ed65f6d7a
Author: Akim Demaille <[email protected]>
Date:   Fri May 1 06:36:19 2020 +0200

    c++: use modern idioms to make classes non-copyable
    
    Reported by Don Macpherson.
    https://lists.gnu.org/r/bug-bison/2019-05/msg00015.html
    https://github.com/akimd/bison/issues/36
    
    * data/skeletons/lalr1.cc, data/skeletons/stack.hh,
    * data/skeletons/variant.hh: Delete the copy-ctor and the copy operator.

diff --git a/THANKS b/THANKS
index 9d49461e..157efc00 100644
--- a/THANKS
+++ b/THANKS
@@ -57,6 +57,7 @@ Derek M. Jones            [email protected]
 Di-an Jan                 [email protected]
 Dick Streefland           [email protected]
 Didier Godefroy           [email protected]
+Don Macpherson            [email protected]
 Efi Fogel                 [email protected]
 Enrico Scholz             [email protected]
 Eric Blake                [email protected]
diff --git a/data/skeletons/lalr1.cc b/data/skeletons/lalr1.cc
index 81aff234..2b27088f 100644
--- a/data/skeletons/lalr1.cc
+++ b/data/skeletons/lalr1.cc
@@ -204,6 +204,13 @@ m4_define([b4_shared_declarations],
     ]b4_parser_class[ (]b4_parse_param_decl[);
     virtual ~]b4_parser_class[ ();
 
+#if 201103L <= YY_CPLUSPLUS
+    /// Non copyable.
+    ]b4_parser_class[ (const ]b4_parser_class[&) = delete;
+    /// Non copyable.
+    ]b4_parser_class[& operator= (const ]b4_parser_class[&) = delete;
+#endif
+
     /// Parse.  An alias for parse ().
     /// \returns  0 iff parsing succeeded.
     int operator() ();
@@ -255,10 +262,13 @@ m4_define([b4_shared_declarations],
     };
 ]])[
   private:
-    /// This class is not copyable.
+#if YY_CPLUSPLUS < 201103L
+    /// Non copyable.
     ]b4_parser_class[ (const ]b4_parser_class[&);
-    ]b4_parser_class[& operator= (const ]b4_parser_class[&);]b4_lac_if([[
-
+    /// Non copyable.
+    ]b4_parser_class[& operator= (const ]b4_parser_class[&);
+#endif
+]b4_lac_if([[
     /// Check the lookahead yytoken.
     /// \returns  true iff the token will be eventually shifted.
     bool yy_lac_check_ (symbol_kind_type yytoken) const;
diff --git a/data/skeletons/stack.hh b/data/skeletons/stack.hh
index 6c41fbf8..0fd36258 100644
--- a/data/skeletons/stack.hh
+++ b/data/skeletons/stack.hh
@@ -41,6 +41,13 @@ m4_define([b4_stack_define],
         : seq_ (n)
       {}
 
+#if 201103L <= YY_CPLUSPLUS
+      /// Non copyable.
+      stack (const stack&) = delete;
+      /// Non copyable.
+      stack& operator= (const stack&) = delete;
+#endif
+
       /// Random access.
       ///
       /// Index 0 returns the topmost element.
@@ -126,8 +133,12 @@ m4_define([b4_stack_define],
       };
 
     private:
+#if YY_CPLUSPLUS < 201103L
+      /// Non copyable.
       stack (const stack&);
+      /// Non copyable.
       stack& operator= (const stack&);
+#endif
       /// The wrapped container.
       S seq_;
     };
diff --git a/data/skeletons/variant.hh b/data/skeletons/variant.hh
index 13a35c6d..b594af38 100644
--- a/data/skeletons/variant.hh
+++ b/data/skeletons/variant.hh
@@ -115,6 +115,13 @@ m4_define([b4_value_type_declare],
       new (yyas_<T> ()) T (YY_MOVE (t));
     }
 
+#if 201103L <= YY_CPLUSPLUS
+    /// Non copyable.
+    semantic_type (const self_type&) = delete;
+    /// Non copyable.
+    self_type& operator= (const self_type&) = delete;
+#endif
+
     /// Destruction, allowed only if empty.
     ~semantic_type () YY_NOEXCEPT
     {]b4_parse_assert_if([
@@ -258,9 +265,12 @@ m4_define([b4_value_type_declare],
     }
 
   private:
-    /// Prohibit blind copies.
-    self_type& operator= (const self_type&);
+#if YY_CPLUSPLUS < 201103L
+    /// Non copyable.
     semantic_type (const self_type&);
+    /// Non copyable.
+    self_type& operator= (const self_type&);
+#endif
 
     /// Accessor to raw memory as \a T.
     template <typename T>