Re: Name clash with token type BEGIN

[Luca]

Il 29/12/2009 21.28, Joel E. Denny ha scritto:
> On Tue, 29 Dec 2009, August Karlstrom wrote:
>
>
> > Joel E. Denny wrote:
> >
> > > I'm guessing your parser.h is included in a scanner generated by Flex, which
> > > defines the macro BEGIN.
> > Yes, that's the case. Do you know if there is there a way around this or do I
> > have to add a prefix to the token (or all tokens for sake of consistency)?
> I think you'll have to change the name somehow.
>
> Bison 2.6 should provide api.tokens.prefix to do this automatically, but
> it's going to be a while before 2.6 is released.
>
>
> > Obviously, the recommendation in the Bison manual of using the same name for a
> > reserved words and its corresponding tokens cannot be followed in the general
> > case when using Flex and Bison in tandem.
> >
> > I guess Flex is to blame here -
> > BEGIN should have been named something like YY_BEGIN.
See PREFIX option:
http://flex.sourceforge.net/manual/Code_002dLevel-And-API-Options.html#Code_002dLevel-And-API-Options
but unfortunately I think BEGIN macro isn't affected.

Please remember a TOKEN is only a define, so if you put inside .y file:
%token MY_BEGIN "BEGIN"
error reporting done by yyerror will always print "BEGIN" and not 
"MY_BEGIN", and you can avoid the conflict.


Maybe there is another workaround (with bison 2.3 or later), you have to 
try:
you can use the enum yytokentype in your code and manually remove the define
 #define BEGIN someint
from your y.tab.h
or you can undefine BEGIN macro in the definition section of lex (before 
the first %%) after including y.tab.h:
http://flex.sourceforge.net/manual/Definitions-Section.html#Definitions-Section

for example
#include y.tab.h
#undef BEGIN
%%
"BEGIN"    {return 268; //you cannot place BEGIN here cos the 
preprocessor use the FLEX macro; keep the number updated!}


Luca

> I agree.  Of course, we're probably a few decades too late to change the
> default Flex behavior, which is inherited from Lex and specified by POSIX.
> However, it would be nice if Flex provided an option to avoid namespace
> pollution.  (If there's something already, I missed it in the manual.)
>
>
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