Re: Bison C++ mid-rule value lost with variants

[Kaz Kylheku]

On 29.06.2017 06:55, Piotr Marcińczyk wrote:
> I supposedly found a bug in lalr1.cc skeleton with variant semantic 
> type.
> When using mid-rule action { $<type>$ = value; } to return a value that
> will be used in further semantic actions, it appears that the value on
> stack becomes zero. Tested with Bison version 3.0.4.

You probably need your code to work with Bison installations
that don't have a fix for this (which is all of them, currently,
except maybe yours).

Could the workaround be as simple as:

   /* plain old local variable, injected into yyparse */

   { int whatever = 42; } + NUM { std::cout << whatever << std::endl; }

Also, you can have a scratch space in your parser structure
for carrying a value from one mid-rule action to another.

   /* assumes %parse-param{your_parser_type *parser} */

   { parser->stash = 42; } + NUM { std::cout << parser->stash << 
std::endl: }

I've done this latter sort of of thing.

The parser structure is basically your "this" object in the entire
parse job, and yyparse is its "method". :)

Cheers ...