[PATCH 01/10] c, c++: also define YYEMPTY in yytoken_kind_t

[Akim Demaille]

I have been hesitating a lot before doing it ---after all the user
must not use this kind, so what's the point of showing it in
yytoken_kind_t.  And eventually I chose to play it safe with the
typing system and make it possible to use yytoken_kind_t for all the
tokens, even the "empty token".

* data/skeletons/c.m4: Give an id and a tag to YYEMPTY.
(b4_token_enums): Define YYEMPTY.
* data/skeletons/c++.m4 (b4_token_enums): Define YYEMPTY.
* data/skeletons/glr.c, data/skeletons/glr.cc, data/skeletons/yacc.c:
(YYEMPTY): Remove.
Use b4_symbol(-2, id) instead.
---
 data/skeletons/c++.m4 |  1 +
 data/skeletons/c.m4   |  5 +++++
 data/skeletons/glr.c  | 30 ++++++++++++++----------------
 data/skeletons/glr.cc |  4 +++-
 data/skeletons/yacc.c | 24 +++++++++++-------------
 5 files changed, 34 insertions(+), 30 deletions(-)

diff --git a/data/skeletons/c++.m4 b/data/skeletons/c++.m4
index 50881770..6617ec3a 100644
--- a/data/skeletons/c++.m4
+++ b/data/skeletons/c++.m4
@@ -173,6 +173,7 @@ 
m4_bpatsubst(m4_dquote(m4_bpatsubst(m4_dquote(b4_namespace_ref[ ]),
 m4_define([b4_token_enums],
 [[enum yytokentype
       {
+        ]b4_symbol([-2], [id])[ = -2,
 ]b4_symbol_foreach([b4_token_enum])dnl
 [      };]dnl
 ])
diff --git a/data/skeletons/c.m4 b/data/skeletons/c.m4
index d095e7a2..fa1f9e1e 100644
--- a/data/skeletons/c.m4
+++ b/data/skeletons/c.m4
@@ -434,11 +434,15 @@ static const b4_int_type_for([$2]) yy$1[[]] =
 # header, and because these tokens are common to all the parsers, we
 # need to make sure their names don't collide: use the api.prefix.
 # YYEOF is special, since the user may give it a different name.
+m4_define([b4_symbol(-2, id)],  [b4_api_PREFIX[][EMPTY]])
+m4_define([b4_symbol(-2, tag)], [[No symbol.]])
+
 m4_if(b4_symbol(0, id), [YYEOF],
      [m4_define([b4_symbol(0, id)],  [b4_api_PREFIX[][EOF]])])
 m4_define([b4_symbol(1, id)],  [b4_api_PREFIX[][ERRCODE]])
 m4_define([b4_symbol(2, id)],  [b4_api_PREFIX[][UNDEF]])
 
+
 # b4_token_define(TOKEN-NUM)
 # --------------------------
 # Output the definition of this token as #define.
@@ -477,6 +481,7 @@ m4_define([b4_token_enums],
 # define ]b4_api_PREFIX[TOKENTYPE
   enum ]b4_api_prefix[tokentype
   {
+    ]b4_symbol([-2], [id])[ = -2,
 ]b4_symbol_foreach([b4_token_enum])dnl
 [  };
   typedef enum ]b4_api_prefix[tokentype ]b4_api_prefix[token_kind_t;
diff --git a/data/skeletons/glr.c b/data/skeletons/glr.c
index 345788d1..b2d54abe 100644
--- a/data/skeletons/glr.c
+++ b/data/skeletons/glr.c
@@ -429,8 +429,6 @@ int yychar;])[
 
 enum { YYENOMEM = -2 };
 
-static const int YYEMPTY = -2;
-
 typedef enum { yyok, yyaccept, yyabort, yyerr } YYRESULTTAG;
 
 #define YYCHK(YYE)                              \
@@ -525,7 +523,7 @@ struct yyGLRStateSet {
   /** During nondeterministic operation, yylookaheadNeeds tracks which
    *  stacks have actually needed the current lookahead.  During deterministic
    *  operation, yylookaheadNeeds[0] is not maintained since it would merely
-   *  duplicate yychar != YYEMPTY.  */
+   *  duplicate yychar != ]b4_symbol(-2, id)[.  */
   yybool* yylookaheadNeeds;
   ptrdiff_t yysize;
   ptrdiff_t yycapacity;
@@ -809,7 +807,7 @@ yygetToken (int *yycharp][]b4_pure_if([, yyGLRStack* 
yystackp])[]b4_user_formals
 {
   yysymbol_kind_t yytoken;
 ]b4_parse_param_use()dnl
-[  if (*yycharp == YYEMPTY)
+[  if (*yycharp == ]b4_symbol(-2, id)[)
     {
       YY_DPRINTF ((stderr, "Reading a token\n"));]b4_glr_cc_if([[
 #if YY_EXCEPTIONS
@@ -887,7 +885,7 @@ yyuserAction (yyRuleNum yyn, int yyrhslen, yyGLRStackItem* 
yyvsp,
 # undef YYRECOVERING
 # define YYRECOVERING() (yystackp->yyerrState != 0)
 # undef yyclearin
-# define yyclearin (yychar = YYEMPTY)
+# define yyclearin (yychar = ]b4_symbol(-2, id)[)
 # undef YYFILL
 # define YYFILL(N) yyfill (yyvsp, &yylow, (N), yynormal)
 # undef YYBACKUP
@@ -1113,7 +1111,7 @@ yyaddDeferredAction (yyGLRStack* yystackp, ptrdiff_t yyk, 
yyGLRState* yystate,
       yynewOption->yyloc = yylloc;])[
     }
   else
-    yynewOption->yyrawchar = YYEMPTY;
+    yynewOption->yyrawchar = ]b4_symbol(-2, id)[;
   yynewOption->yynext = yystate->yysemantics.yyfirstVal;
   yystate->yysemantics.yyfirstVal = yynewOption;
 
@@ -2134,7 +2132,7 @@ static yysymbol_kind_t
 yypcontext_token (const yyGLRStack *yystackp)
 {
   YYUSE (yystackp);
-  yysymbol_kind_t yytoken = yychar == YYEMPTY ? ]b4_symbol_prefix[YYEMPTY : 
YYTRANSLATE (yychar);
+  yysymbol_kind_t yytoken = yychar == ]b4_symbol(-2, id)[ ? 
]b4_symbol_prefix[YYEMPTY : YYTRANSLATE (yychar);
   return yytoken;
 }
 
@@ -2153,7 +2151,7 @@ yypcontext_location (const yyGLRStack *yystackp)
 yy_syntax_error_arguments (const yyGLRStack* yystackp,
                            yysymbol_kind_t yyarg[], int yyargn)
 {
-  yysymbol_kind_t yytoken = yychar == YYEMPTY ? ]b4_symbol_prefix[YYEMPTY : 
YYTRANSLATE (yychar);
+  yysymbol_kind_t yytoken = yychar == ]b4_symbol(-2, id)[ ? 
]b4_symbol_prefix[YYEMPTY : YYTRANSLATE (yychar);
   /* Actual size of YYARG. */
   int yycount = 0;
   /* There are many possibilities here to consider:
@@ -2313,7 +2311,7 @@ yyrecoverSyntaxError (yyGLRStack* 
yystackp]b4_user_formals[)
         int yyj;
         if (yychar == ]b4_symbol(0, [id])[)
           yyFail (yystackp][]b4_lpure_args[, YY_NULLPTR);
-        if (yychar != YYEMPTY)
+        if (yychar != ]b4_symbol(-2, id)[)
           {]b4_locations_if([[
             /* We throw away the lookahead, but the error range
                of the shifted error token must take it into account.  */
@@ -2325,7 +2323,7 @@ yyrecoverSyntaxError (yyGLRStack* 
yystackp]b4_user_formals[)
             yytoken = YYTRANSLATE (yychar);
             yydestruct ("Error: discarding",
                         yytoken, &yylval]b4_locuser_args([&yylloc])[);
-            yychar = YYEMPTY;
+            yychar = ]b4_symbol(-2, id)[;
           }
         yytoken = ]b4_yygetToken_call[;
         yyj = yypact[yystackp->yytops.yystates[0]->yylrState];
@@ -2422,7 +2420,7 @@ yyparse (]m4_ifset([b4_parse_param], 
[b4_formals(b4_parse_param)], [void])[)
 
   YY_DPRINTF ((stderr, "Starting parse\n"));
 
-  yychar = YYEMPTY;
+  yychar = ]b4_symbol(-2, id)[;
   yylval = yyval_default;]b4_locations_if([
   yylloc = yyloc_default;])[
 ]m4_ifdef([b4_initial_action], [
@@ -2475,7 +2473,7 @@ b4_dollar_popdef])[]dnl
               if (yyisShiftAction (yyaction))
                 {
                   YY_SYMBOL_PRINT ("Shifting", yytoken, &yylval, &yylloc);
-                  yychar = YYEMPTY;
+                  yychar = ]b4_symbol(-2, id)[;
                   yyposn += 1;
                   yyglrShift (&yystack, 0, yyaction, yyposn, 
&yylval]b4_locations_if([, &yylloc])[);
                   if (0 < yystack.yyerrState)
@@ -2501,7 +2499,7 @@ b4_dollar_popdef])[]dnl
           ptrdiff_t yys;
 
           for (yys = 0; yys < yystack.yytops.yysize; yys += 1)
-            yystackp->yytops.yylookaheadNeeds[yys] = yychar != YYEMPTY;
+            yystackp->yytops.yylookaheadNeeds[yys] = yychar != ]b4_symbol(-2, 
id)[;
 
           /* yyprocessOneStack returns one of three things:
 
@@ -2539,11 +2537,11 @@ b4_dollar_popdef])[]dnl
 
           /* If any yyglrShift call fails, it will fail after shifting.  Thus,
              a copy of yylval will already be on stack 0 in the event of a
-             failure in the following loop.  Thus, yychar is set to YYEMPTY
+             failure in the following loop.  Thus, yychar is set to 
]b4_symbol(-2, id)[
              before the loop to make sure the user destructor for yylval isn't
              called twice.  */
           yytoken_to_shift = YYTRANSLATE (yychar);
-          yychar = YYEMPTY;
+          yychar = ]b4_symbol(-2, id)[;
           yyposn += 1;
           for (yys = 0; yys < yystack.yytops.yysize; yys += 1)
             {
@@ -2593,7 +2591,7 @@ b4_dollar_popdef])[]dnl
   goto yyreturn;
 
  yyreturn:
-  if (yychar != YYEMPTY)
+  if (yychar != ]b4_symbol(-2, id)[)
     yydestruct ("Cleanup: discarding lookahead",
                 YYTRANSLATE (yychar), &yylval]b4_locuser_args([&yylloc])[);
 
diff --git a/data/skeletons/glr.cc b/data/skeletons/glr.cc
index c6159c3a..8eb762cf 100644
--- a/data/skeletons/glr.cc
+++ b/data/skeletons/glr.cc
@@ -340,7 +340,9 @@ b4_percent_define_flag_if([[global_tokens_and_yystype]],
 ]b4_namespace_close[
 
 ]dnl Map the name used in c.m4 to the one used in c++.m4.
-[#undef ]b4_symbol(0, [id])[
+[#undef ]b4_symbol(-2, [id])[
+#define ]b4_symbol(-2, [id])[ 
]b4_namespace_ref[::]b4_parser_class[::token::]b4_symbol(-2, [id])[
+#undef ]b4_symbol(0, [id])[
 #define ]b4_symbol(0, [id])[ 
]b4_namespace_ref[::]b4_parser_class[::token::]b4_symbol(0, [id])[
 
 #ifndef ]b4_api_PREFIX[STYPE
diff --git a/data/skeletons/yacc.c b/data/skeletons/yacc.c
index b71c1ff5..3487cd66 100644
--- a/data/skeletons/yacc.c
+++ b/data/skeletons/yacc.c
@@ -714,8 +714,7 @@ static const ]b4_int_type_for([b4_toknum])[ yytoknum[] =
 enum { YYENOMEM = -2 };
 
 #define yyerrok         (yyerrstatus = 0)
-#define yyclearin       (yychar = YYEMPTY)
-#define YYEMPTY         (-2)
+#define yyclearin       (yychar = ]b4_symbol(-2, id)[)
 
 #define YYACCEPT        goto yyacceptlab
 #define YYABORT         goto yyabortlab
@@ -726,7 +725,7 @@ enum { YYENOMEM = -2 };
 
 #define YYBACKUP(Token, Value)                                    \
   do                                                              \
-    if (yychar == YYEMPTY)                                        \
+    if (yychar == ]b4_symbol(-2, id)[)                                        \
       {                                                           \
         yychar = (Token);                                         \
         yylval = (Value);                                         \
@@ -1613,7 +1612,7 @@ b4_initialize_parser_state_variables])[
 
   YYDPRINTF ((stderr, "Starting parse\n"));
 
-  yychar = YYEMPTY; /* Cause a token to be read.  */
+  yychar = ]b4_symbol(-2, id)[; /* Cause a token to be read.  */
 ]m4_ifdef([b4_initial_action], [
 b4_dollar_pushdef([m4_define([b4_dollar_dollar_used])yylval], [], [],
                   [b4_push_if([b4_pure_if([*])yypushed_loc], [yylloc])])dnl
@@ -1735,7 +1734,7 @@ yybackup:
   /* Not known => get a lookahead token if don't already have one.  */
 
   /* YYCHAR is either empty, or end-of-input, or a valid lookahead.  */
-  if (yychar == YYEMPTY)
+  if (yychar == ]b4_symbol(-2, id)[)
     {]b4_push_if([[
       if (!yyps->yynew)
         {]b4_use_push_for_pull_if([], [[
@@ -1763,7 +1762,7 @@ yyread_pushed_token:]])[
   if (yychar <= ]b4_symbol(0, [id])[)
     {
       yychar = ]b4_symbol(0, [id])[;
-      yytoken = ]b4_symbol_prefix[YYEOF;
+      yytoken = ]b4_symbol(0, [kind])[;
       YYDPRINTF ((stderr, "Now at end of input.\n"));
     }
   else
@@ -1805,7 +1804,7 @@ yyread_pushed_token:]])[
   *++yylsp = yylloc;])[
 
   /* Discard the shifted token.  */
-  yychar = YYEMPTY;]b4_lac_if([[
+  yychar = ]b4_symbol(-2, id)[;]b4_lac_if([[
   YY_LAC_DISCARD ("shift");]])[
   goto yynewstate;
 
@@ -1896,8 +1895,7 @@ yyreduce:
 yyerrlab:
   /* Make sure we have latest lookahead translation.  See comments at
      user semantic actions for why this is necessary.  */
-  yytoken = yychar == YYEMPTY ? ]b4_symbol_prefix[YYEMPTY : YYTRANSLATE 
(yychar);
-
+  yytoken = yychar == ]b4_symbol(-2, id)[ ? ]b4_symbol_prefix[YYEMPTY : 
YYTRANSLATE (yychar);
   /* If not already recovering from an error, report this error.  */
   if (!yyerrstatus)
     {
@@ -1907,7 +1905,7 @@ yyerrlab:
 [[      {
         yypcontext_t yyctx
           = {]b4_push_if([[yyps]], [[yyssp]b4_lac_if([[, yyesa, &yyes, 
&yyes_capacity]])])[, yytoken]b4_locations_if([[, &yylloc]])[};]b4_lac_if([[
-        if (yychar != YYEMPTY)
+        if (yychar != ]b4_symbol(-2, id)[)
           YY_LAC_ESTABLISH;]])[
         if (yyreport_syntax_error (&yyctx]m4_ifset([b4_parse_param],
                                   [[, ]b4_args(b4_parse_param)])[) == 2)
@@ -1920,7 +1918,7 @@ yyerrlab:
           = {]b4_push_if([[yyps]], [[yyssp]b4_lac_if([[, yyesa, &yyes, 
&yyes_capacity]])])[, yytoken]b4_locations_if([[, &yylloc]])[};
         char const *yymsgp = YY_("syntax error");
         int yysyntax_error_status;]b4_lac_if([[
-        if (yychar != YYEMPTY)
+        if (yychar != ]b4_symbol(-2, id)[)
           YY_LAC_ESTABLISH;]])[
         yysyntax_error_status = yysyntax_error (&yymsg_alloc, &yymsg, &yyctx);
         if (yysyntax_error_status == 0)
@@ -1967,7 +1965,7 @@ yyerrlab:
         {
           yydestruct ("Error: discarding",
                       yytoken, &yylval]b4_locations_if([, 
&yylloc])[]b4_user_args[);
-          yychar = YYEMPTY;
+          yychar = ]b4_symbol(-2, id)[;
         }
     }
 
@@ -2078,7 +2076,7 @@ yyexhaustedlab:
 | yyreturn -- parsing is finished, return the result.  |
 `-----------------------------------------------------*/
 yyreturn:
-  if (yychar != YYEMPTY)
+  if (yychar != ]b4_symbol(-2, id)[)
     {
       /* Make sure we have latest lookahead translation.  See comments at
          user semantic actions for why this is necessary.  */
-- 
2.26.0