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Overview
Comment:Enhance Lemon and the parser template so that it can once again build parsers that have no unreachable branches.
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SHA1:41fd46e2962ba9a1e1f6867567499d1f6f5b8372
User & Date: drh 2016-05-24 18:55:08
Context
2016-05-25
18:53
Add the libvers.c tool in the tool/ subdirectory. check-in: 2a41f098 user: drh tags: trunk
2016-05-24
18:55
Enhance Lemon and the parser template so that it can once again build parsers that have no unreachable branches. check-in: 41fd46e2 user: drh tags: trunk
18:50
Minor change to the walcrash4.test module so that it works when SQLITE_DEFAULT_WAL_SYNCHRONOUS is set to something other than 2. check-in: 61e239bc user: drh tags: trunk
Changes
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Changes to tool/lemon.c.

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  const char *codeSuffix;  /* Breakdown code after code[] above */
  int noCode;              /* True if this rule has no associated C code */
  int codeEmitted;         /* True if the code has been emitted already */
  struct symbol *precsym;  /* Precedence symbol for this rule */
  int index;               /* An index number for this rule */
  int iRule;               /* Rule number as used in the generated tables */
  Boolean canReduce;       /* True if this rule is ever reduced */

  struct rule *nextlhs;    /* Next rule with the same LHS */
  struct rule *next;       /* Next rule in the global list */
};

/* A configuration is a production rule of the grammar together with
** a mark (dot) showing how much of that rule has been processed so far.
** Configurations also contain a follow-set which is a list of terminal
................................................................................
      printf("%4d: State %3d %s n: %2d size: %5d freespace: %d\n",
             i, stp->statenum, ax[i].isTkn ? "Token" : "Var  ",
             ax[i].nAction, pActtab->nAction, nn);
    }
#endif
  }
  free(ax);














  /* Finish rendering the constants now that the action table has
  ** been computed */
  fprintf(out,"#define YYNSTATE             %d\n",lemp->nxstate);  lineno++;
  fprintf(out,"#define YYNRULE              %d\n",lemp->nrule);  lineno++;
  fprintf(out,"#define YY_MAX_SHIFT         %d\n",lemp->nxstate-1); lineno++;
  fprintf(out,"#define YY_MIN_SHIFTREDUCE   %d\n",lemp->nstate); lineno++;
................................................................................
  ** empty actions. */
  fprintf(out,"      default:\n"); lineno++;
  for(rp=lemp->rule; rp; rp=rp->next){
    if( rp->codeEmitted ) continue;
    assert( rp->noCode );
    fprintf(out,"      /* (%d) ", rp->iRule);
    writeRuleText(out, rp);

    fprintf(out, " */ yytestcase(yyruleno==%d);\n", rp->iRule); lineno++;




  }
  fprintf(out,"        break;\n"); lineno++;
  tplt_xfer(lemp->name,in,out,&lineno);

  /* Generate code which executes if a parse fails */
  tplt_print(out,lemp,lemp->failure,&lineno);
  tplt_xfer(lemp->name,in,out,&lineno);







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  const char *codeSuffix;  /* Breakdown code after code[] above */
  int noCode;              /* True if this rule has no associated C code */
  int codeEmitted;         /* True if the code has been emitted already */
  struct symbol *precsym;  /* Precedence symbol for this rule */
  int index;               /* An index number for this rule */
  int iRule;               /* Rule number as used in the generated tables */
  Boolean canReduce;       /* True if this rule is ever reduced */
  Boolean doesReduce;      /* Reduce actions occur after optimization */
  struct rule *nextlhs;    /* Next rule with the same LHS */
  struct rule *next;       /* Next rule in the global list */
};

/* A configuration is a production rule of the grammar together with
** a mark (dot) showing how much of that rule has been processed so far.
** Configurations also contain a follow-set which is a list of terminal
................................................................................
      printf("%4d: State %3d %s n: %2d size: %5d freespace: %d\n",
             i, stp->statenum, ax[i].isTkn ? "Token" : "Var  ",
             ax[i].nAction, pActtab->nAction, nn);
    }
#endif
  }
  free(ax);

  /* Mark rules that are actually used for reduce actions after all
  ** optimizations have been applied
  */
  for(rp=lemp->rule; rp; rp=rp->next) rp->doesReduce = LEMON_FALSE;
  for(i=0; i<lemp->nxstate; i++){
    struct action *ap;
    for(ap=lemp->sorted[i]->ap; ap; ap=ap->next){
      if( ap->type==REDUCE || ap->type==SHIFTREDUCE ){
        ap->x.rp->doesReduce = i;
      }
    }
  }

  /* Finish rendering the constants now that the action table has
  ** been computed */
  fprintf(out,"#define YYNSTATE             %d\n",lemp->nxstate);  lineno++;
  fprintf(out,"#define YYNRULE              %d\n",lemp->nrule);  lineno++;
  fprintf(out,"#define YY_MAX_SHIFT         %d\n",lemp->nxstate-1); lineno++;
  fprintf(out,"#define YY_MIN_SHIFTREDUCE   %d\n",lemp->nstate); lineno++;
................................................................................
  ** empty actions. */
  fprintf(out,"      default:\n"); lineno++;
  for(rp=lemp->rule; rp; rp=rp->next){
    if( rp->codeEmitted ) continue;
    assert( rp->noCode );
    fprintf(out,"      /* (%d) ", rp->iRule);
    writeRuleText(out, rp);
    if( rp->doesReduce ){
      fprintf(out, " */ yytestcase(yyruleno==%d);\n", rp->iRule); lineno++;
    }else{
      fprintf(out, " (OPTIMIZED OUT) */ assert(yyruleno!=%d);\n",
              rp->iRule); lineno++;
    }
  }
  fprintf(out,"        break;\n"); lineno++;
  tplt_xfer(lemp->name,in,out,&lineno);

  /* Generate code which executes if a parse fails */
  tplt_print(out,lemp,lemp->failure,&lineno);
  tplt_xfer(lemp->name,in,out,&lineno);

Changes to tool/lempar.c.

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){
  ParseARG_FETCH;
#ifndef NDEBUG
  if( yyTraceFILE ){
    fprintf(yyTraceFILE,"%sAccept!\n",yyTracePrompt);
  }
#endif
  while( yypParser->yytos>yypParser->yystack ) yy_pop_parser_stack(yypParser);
  /* Here code is inserted which will be executed whenever the
  ** parser accepts */
/*********** Begin %parse_accept code *****************************************/
%%
/*********** End %parse_accept code *******************************************/
  ParseARG_STORE; /* Suppress warning about unused %extra_argument variable */
}







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){
  ParseARG_FETCH;
#ifndef NDEBUG
  if( yyTraceFILE ){
    fprintf(yyTraceFILE,"%sAccept!\n",yyTracePrompt);
  }
#endif
  assert( yypParser->yytos==yypParser->yystack );
  /* Here code is inserted which will be executed whenever the
  ** parser accepts */
/*********** Begin %parse_accept code *****************************************/
%%
/*********** End %parse_accept code *******************************************/
  ParseARG_STORE; /* Suppress warning about unused %extra_argument variable */
}