Re: set_goto_map() has unintentional ++ operator

[sean nakasone]

Hi Akim, I didn't test it, nor did I run it in a debugger..  so there must be 
something I'm not seeing.

The placement of the ++ makes it a post increment, so it's incremented after 
the statement, so it should not affect the value of k.

It's incrementing values in temp_map, but temp_map is deallocated after the for 
loop, so that's why I thought it wasn't doing anything.

  for (s = 0; s < nstates; ++s)
    {
      transitions *sp = states[s]->transitions;
      int i;
      for (i = sp->num - 1; i >= 0 && TRANSITION_IS_GOTO (sp, i); --i)
        {
          goto_number k = temp_map[TRANSITION_SYMBOL (sp, i) - ntokens]++;
          from_state[k] = s;
          to_state[k] = sp->states[i]->number;
        }
    }

  free (temp_map);



I appreciate your efforts and follow up.



--------------------------------------------
On Mon, 12/29/14, Akim Demaille <address@hidden> wrote:

 Subject: Re: set_goto_map() has unintentional ++ operator
 To: "Sean Nakasone" <address@hidden>
 Cc: "Bison Help" <address@hidden>
 Date: Monday, December 29, 2014, 5:29 AM
 
 
 > Le
 21 déc. 2014 à 21:51, Sean Nakasone <address@hidden>
 a écrit :
 > 
 > in
 lalr.c
 > 
 > the ++ at
 the end of the following line doesn't have a purpose
 > 
 > goto_number k =
 temp_map[TRANSITION_SYMBOL(sp, i) - ntokens]++;
 > 
 > it can be
 misleading. 
 
 hi Sean,
 
 Well, this piece of code is
 old, and it does not seem immediate
 (to me)
 that the ++ is useless :)
 
   from_state = xcalloc (ngotos, sizeof
 *from_state);
   to_state = xcalloc (ngotos,
 sizeof *to_state);
 
   for
 (s = 0; s < nstates; ++s)
     {
       transitions *sp =
 states[s]->transitions;
       int
 i;
       for (i = sp->num - 1; i >=
 0 && TRANSITION_IS_GOTO (sp, i); --i)
         {
          
 goto_number k = temp_map[TRANSITION_SYMBOL (sp, i) -
 ntokens]++;
           from_state[k] =
 s;
           to_state[k] =
 sp->states[i]->number;
        
 }
     }
 
   free (temp_map);
 
 FTR, byacc (beach and bison are forks of a
 common ancestor) reads:
 
  
   from_state = NEW2(ngotos, Value_t);
    
 to_state = NEW2(ngotos, Value_t);
 
     for (sp = first_shift; sp; sp =
 sp->next)
     {
    
 state1 = sp->number;
     for (i =
 sp->nshifts - 1; i >= 0; i--)
    
 {
         state2 = sp->shift[i];
         symbol =
 accessing_symbol[state2];
 
         if (ISTOKEN(symbol))
         break;
 
         k = temp_map[symbol]++;
         from_state[k] = state1;
         to_state[k] = state2;
     }
     }
 
     FREE(temp_map +
 ntokens);
 
 it has the same
 ++.
 
 
 What
 makes you think it is useless?  If I remove it, some tests
 fail
 (they hang), or I can even get a
 SEGV.
 
 $ cat input.y
 %%
 start: end end {} ;
 end:
 { }  ;
 $ ./_build/35s/tests/bison
 input.y
 ./_build/35s/tests/bison: line 28:
 87593 Segmentation fault: 11  $PREBISON
 "$abs_top_builddir/src/bison"
 ${1+"$@"}
 
 
 
 _______________________________________________
 address@hidden
 https://lists.gnu.org/mailman/listinfo/help-bison