Debug mode without using "-d"

Hi there,

I'm a Bison beginner, just started to play with a demo.

I see there is a "-d" command line option, which shows some debug
information.

I'ld like to control this feature through my code. I realized
that this option set a variable in generated source file:

  1577  extern int yy_flex_debug;
  1578  int yy_flex_debug = 1;

  ... 

  1657  void yyset_debug ( int debug_flag  );

  ...

  3254  void yyset_debug (int  _bdebug )
  3255  {
  3256          yy_flex_debug = _bdebug ;
  3257  }


Okay, I tried to use this variable with this way in my own
source:

int main(int argc, char* argv[]) {

    if (argc > 1) {
        if (strcmp(argv[1], "debug") == 0) {
            yyset_debug(1);
        }
    ...

but has no effect (if I use "flex" command without "-d").

What am I missing?


Thanks,


a.