Re: [PATCH 5/6] lalr1.cc: add LAC support

[Akim Demaille]

Hi Adrian,

> Le 9 août 2019 à 10:18, Adrian Vogelsgesang <address@hidden> a écrit :
> 
> Hi Akim,
> 
> I see you fixed the outstanding issue regarding yylac_stack_ being a stack 
> with complete symbols:
> 
>> There's an issue I had not paid attention to: you made a lac_stack_
>> a fully blown stack of symbols (i.e., type, value and location).  I
>> believe you only need a stack a states, the rest is useless. 
> 
> and replaced it by a std::vector. Thanks for taking care of that! :)
> 
> One minor nitpick:
> I think
>    +          if (yylen < lac_size)
>    +            {
>    +              for (size_t i = 0; i < yylen; ++i)
>    +                yylac_stack_.pop_back ();
>    +              yylen = 0;
>    +            }
> could now be written as
>    +          if (yylen < lac_size)
>    +            {
>    +              yylac_stack_.resize(lac_size - yylen);
>    +              yylen = 0;
>    +            }
> 
> Didn't test it, though - so maybe I am missing something obvious.
> Also, I guess/hope the compiler will optimize that out anyway.

You are right, thanks for catching this.  I've installed the following
patch.

Cheers!

commit d7cf3f5b181401f42ba5a8586d12885cfb844639
Author: Akim Demaille <address@hidden>
Date:   Sun Aug 18 06:54:56 2019 -0500

    c++: use resize to shrink a vector
    
    Suggested by Adrian Vogelsgesang.
    https://lists.gnu.org/archive/html/bison-patches/2019-08/msg00009.html
    
    * data/skeletons/lalr1.cc (yy_lac_check_): here.

diff --git a/data/skeletons/lalr1.cc b/data/skeletons/lalr1.cc
index 37c12f7d..cf11fba3 100644
--- a/data/skeletons/lalr1.cc
+++ b/data/skeletons/lalr1.cc
@@ -1182,8 +1182,7 @@ b4_dollar_popdef])[]dnl
           size_t lac_size = yylac_stack_.size ();
           if (yylen < lac_size)
             {
-              for (size_t i = 0; i < yylen; ++i)
-                yylac_stack_.pop_back ();
+              yylac_stack_.resize (lac_size - yylen);
               yylen = 0;
             }
           else if (lac_size)