Re: Duplicate definition of YYUSE macro

[Akim Demaille]

Hi Frank!

> Le 30 juin 2019 à 02:26, Frank Heckenbach <address@hidden> a écrit :
> 
> [...]
> 
> So I looked in the generated file and found this:
> 
> // ...
> 
> /* Suppress unused-variable warnings by "using" E.  */
> #if ! defined lint || defined __GNUC__
> # define YYUSE(E) ((void) (E))
> #else
> # define YYUSE(E) /* empty */
> #endif
> 
> // ...
> 
> // Suppress unused-variable warnings by "using" E.
> #define YYUSE(E) ((void) (E))
> 
> // ...
> 
>    YYUSE (yysym.type_get ());
> 
> So YYUSE is in fact used, but after being defined twice.

Nice one :)  Thanks for reporting this!  The C++ skeletons now indeed
benefit from the definition in C.

> However, as far as Bison is concerned, I wonder if it's actually
> intended that the macro is defined twice, and in fact both
> definitions might differ, depending on the conditionals.

Yes, I agree, it's wrong.

> AFAICS, the two definitions come from c.m4 and lalr1.cc,
> respectively. Since the latter uses the former (via c++.m4), it
> seems the second one can safely be removed. I just tested it with
> split-header and single-file parsers and found no difference, except
> for the above warning disappearing.

Bison's test suite is also happy with this change.

Thanks a lot!

commit afc219a7657a482fedad8ded786f3400f8ea105f
Author: Akim Demaille <address@hidden>
Date:   Sun Jun 30 19:19:43 2019 +0200

    c++: avoid duplicate definition of YYUSE
    
    Reported by Frank Heckenbach.
    https://lists.gnu.org/archive/html/bug-bison/2019-06/msg00009.html
    
    * data/skeletons/lalr1.cc (b4_shared_declarations): Remove the
    duplicate definition of YYUSE, the other one coming from
    b4_attribute_define.

diff --git a/data/skeletons/lalr1.cc b/data/skeletons/lalr1.cc
index ef5d76f5..d1c30403 100644
--- a/data/skeletons/lalr1.cc
+++ b/data/skeletons/lalr1.cc
@@ -459,9 +459,6 @@ m4_if(b4_prefix, [yy], [],
 [#define YYRHSLOC(Rhs, K) ((Rhs)[K].location)
 ]b4_yylloc_default_define])[
 
-// Suppress unused-variable warnings by "using" E.
-#define YYUSE(E) ((void) (E))
-
 // Enable debugging if requested.
 #if ]b4_api_PREFIX[DEBUG