yacc: use the most appropriate integral type for state numbers

Currently we properly use the "best" integral type for tables,
including those storing state numbers.  However the variables for
state numbers used in yyparse (and its dependencies such as
yy_stack_print) still use int16_t invariably.  As a consequence, very
large models overflow these variables.

Let's use the "best" type for these variables too.  It turns out that
we can still use 16 bits for twice larger automata: stick to unsigned
types.

However using 'unsigned' when 16 bits are not enough is troublesome
and generates tons of warnings about signedness issues.  Instead,
let's use 'int'.

Reported by Tom Kramer.
https://lists.gnu.org/archive/html/bug-bison/2019-09/msg00018.html

* data/skeletons/yacc.c (b4_state_num_type): New.
(yy_state_num): Be computed from YYNSTATES.
* tests/linear: New.
* tests/torture.at (State number type): New.
Use it.

THANKS

@@ -179,6 +179,7 @@ Tim Landscheidt           tim@tim-landscheidt.de
 Tim Van Holder            tim.van.holder@pandora.be
 Tobias Frost              tobi@debian.org
 Todd Freed                todd.freed@gmail.com
+Tom Kramer                kramer@nist.gov
 Tom Lane                  tgl@sss.pgh.pa.us
 Tom Tromey                tromey@cygnus.com
 Tomasz Kłoczko            kloczko.tomasz@gmail.com

data/skeletons/yacc.c

@@ -127,6 +127,18 @@ m4_define([b4_int_type],
 
                                                [int])])
 
+# b4_state_num_type(MIN, MAX)
+# ---------------------------
+# Likewise, but prefer 'int' to 'unsigned' for large integers.
+m4_define([b4_state_num_type],
+[m4_if(b4_ints_in($@,      [0],   [255]), [1], [yytype_uint8],
+       b4_ints_in($@,   [-128],   [127]), [1], [yytype_int8],
+
+       b4_ints_in($@,      [0], [65535]), [1], [yytype_uint16],
+       b4_ints_in($@, [-32768], [32767]), [1], [yytype_int16],
+
+                                               [int])])
+
 
 ## ----------------- ##
 ## Semantic Values.  ##
@@ -432,7 +444,7 @@ typedef short yytype_int16;
 
 
 /* State numbers. */
-typedef yytype_int16 yy_state_num;
+typedef ]b4_state_num_type(0, m4_eval(b4_states_number - 1))[ yy_state_num;
 
 
 #ifndef YY_
@@ -740,10 +752,7 @@ do {                                                                      \
 {
   YYFPRINTF (stderr, "Stack now");
   for (; yybottom <= yytop; yybottom++)
-    {
+    YYFPRINTF (stderr, " %u", (unsigned) *yybottom);
-      int yybot = *yybottom;
-      YYFPRINTF (stderr, " %d", yybot);
-    }
   YYFPRINTF (stderr, "\n");
 }
 
@@ -985,7 +994,7 @@ yy_lac (yy_state_num *yyesa, yy_state_num **yyes,
         }
       else
         {
-          yyrule = yytable[yyrule];
+          yyrule = (int) yytable[yyrule];
           if (yytable_value_is_error (yyrule))
             {
               YYDPRINTF ((stderr, " Err\n"));
@@ -1022,11 +1031,10 @@ yy_lac (yy_state_num *yyesa, yy_state_num **yyes,
         int yystate;
         {
           const int yylhs = yyr1[yyrule] - YYNTOKENS;
-          const int yyi = yypgoto[yylhs] + *yyesp;
+          const int yyi = yypgoto[yylhs] + (int) *yyesp;
-          yystate = ((yy_state_num)
+          yystate = (0 <= yyi && yyi <= YYLAST && yycheck[yyi] == *yyesp
-                     (0 <= yyi && yyi <= YYLAST && yycheck[yyi] == *yyesp
+                     ? (int) yytable[yyi]
-                      ? yytable[yyi]
+                     : yydefgoto[yylhs]);
-                      : yydefgoto[yylhs]));
         }
         if (yyesp == yyes_prev)
           {
@@ -1046,7 +1054,7 @@ yy_lac (yy_state_num *yyesa, yy_state_num **yyes,
               }
             *++yyesp = (yy_state_num) yystate;
           }
-        YYDPRINTF ((stderr, " G%d", (int) yystate));
+        YYDPRINTF ((stderr, " G%d", yystate));
       }
     }
 }]])[
@@ -1639,7 +1647,7 @@ yyread_pushed_token:]])[
       goto yydefault;
     }]], [[
     goto yydefault;]])[
-  yyn = yytable[yyn];
+  yyn = (int) yytable[yyn];
   if (yyn <= 0)
     {
       if (yytable_value_is_error (yyn))
@@ -1661,7 +1669,7 @@ yyread_pushed_token:]])[
   yychar = YYEMPTY;]b4_lac_if([[
   YY_LAC_DISCARD ("shift");]])[
 
-  yystate = (yy_state_num) yyn;
+  yystate = yyn;
   YY_IGNORE_MAYBE_UNINITIALIZED_BEGIN
   *++yyvsp = yylval;
   YY_IGNORE_MAYBE_UNINITIALIZED_END]b4_locations_if([
@@ -1741,9 +1749,9 @@ yyreduce:
      number reduced by.  */
   {
     const int yylhs = yyr1[yyn] - YYNTOKENS;
-    const int yyi = yypgoto[yylhs] + *yyssp;
+    const int yyi = yypgoto[yylhs] + (int) *yyssp;
     yystate = (0 <= yyi && yyi <= YYLAST && yycheck[yyi] == *yyssp
-               ? yytable[yyi]
+               ? (int) yytable[yyi]
                : yydefgoto[yylhs]);
   }
 
@@ -1859,7 +1867,7 @@ yyerrlab1:
           yyn += YYTERROR;
           if (0 <= yyn && yyn <= YYLAST && yycheck[yyn] == YYTERROR)
             {
-              yyn = yytable[yyn];
+              yyn = (int) yytable[yyn];
               if (0 < yyn)
                 break;
             }
@@ -1894,7 +1902,7 @@ yyerrlab1:
   /* Shift the error token.  */
   YY_SYMBOL_PRINT ("Shifting", yystos[yyn], yyvsp, yylsp);
 
-  yystate = (yy_state_num) yyn;
+  yystate = yyn;
   goto yynewstate;
 
 

tests/linear

@@ -0,0 +1,94 @@
+#! /usr/bin/env ruby
+
+# Build a grammar whose LALR(1) parser has a given number of states.
+# Useful to test edge cases (e.g., 256 and 257 states, etc.).
+
+class Linear
+  def initialize(states)
+    @states = states - 4
+    @cols = Math.sqrt(@states).to_i
+    @lines = @states / @cols
+    @rest = @states % @cols
+
+    @n = @lines * (@cols - 1) + (@rest == 0 ? 1 : @rest == 1 ? 2 : @rest)
+  end
+
+  def nterms
+    last = @lines + ([0, 1].include?(@rest) ? 0 : 1)
+    (0...last).map { |i| "t#{i}" }.join(' ')
+  end
+
+  def rules
+    res = (0...@lines).map { |i| "t#{i}:#{' N' * (@cols - 1)}" }.join("\n")
+    case @rest
+    when 0
+      res += ' N'
+    when 1
+      res += ' N N'
+    else
+      res += "\nt#{@lines}:#{" N" * @rest}"
+    end
+    res
+  end
+
+  def to_s
+    puts <<~EOF
+      // states: #{@states}
+      // cols: #{@cols}
+      // lines: #{@lines}
+      // rest: #{@rest}
+      // n: #{@n}
+
+      %code {
+        #include <stdio.h>
+        #include <stdlib.h>
+
+        static int yylex (void);
+        static void yyerror (const char *msg);
+       }
+
+      %debug
+      %define api.value.type union
+      %define parse.lac full
+      %define parse.error verbose
+      %printer { fprintf (yyo, "%ld", $$); } <long>
+      %token <long> N
+
+      %%
+
+      exp: #{nterms}
+
+      #{rules}
+
+      %%
+
+      static
+      int yylex (void)
+      {
+        static long count = 0;
+        if (count++ < #{@n})
+          {
+            yylval.N = count;
+            return N;
+          }
+        else
+          return 0;
+      }
+
+      static
+      void yyerror (const char *msg)
+      {
+        fprintf (stderr, "%s\\n", msg);
+      }
+
+      int
+      main (void)
+      {
+        yydebug = !!getenv ("YYDEBUG");
+        return yyparse ();
+      }
+      EOF
+  end
+end
+
+puts Linear.new(ARGV[0].to_i).to_s

tests/local.mk

@@ -15,7 +15,7 @@
 ## You should have received a copy of the GNU General Public License
 ## along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
-EXTRA_DIST += $(TESTSUITE_AT) %D%/testsuite %D%/testsuite.h
+EXTRA_DIST += %D%/linear $(TESTSUITE_AT) %D%/testsuite %D%/testsuite.h
 
 DISTCLEANFILES       += %D%/atconfig $(check_SCRIPTS)
 MAINTAINERCLEANFILES += $(TESTSUITE)

tests/torture.at

@@ -233,7 +233,7 @@ AT_DATA_HORIZONTAL_GRAMMAR([input.y], [1000])
 # Ask for 200 MiB, which should be plenty even on a 64-bit host.
 AT_INCREASE_DATA_SIZE(204000)
 
-AT_BISON_CHECK_NO_XML([-v -o input.c input.y])
+AT_BISON_CHECK_NO_XML([-o input.c input.y])
 AT_COMPILE([input])
 AT_PARSER_CHECK([input])
 
@@ -241,6 +241,43 @@ AT_CLEANUP
 
 
 
+## ------------------- ##
+## State number type.  ##
+## ------------------- ##
+
+# AT_TEST(NUM-STATES, TYPE)
+# -------------------------
+# Check that automaton with NUM-STATES uses TYPE has state number type.
+# Check that parser works.
+
+m4_pushdef([AT_TEST],
+[AT_SETUP([State number type: $1 states])
+
+AT_BISON_OPTION_PUSHDEFS
+
+AT_CHECK([ruby $abs_top_srcdir/tests/linear $1 >input.y || { echo "ruby does not work"; exit 77; }])
+# Old versions of GCC reject large values given to #line.
+AT_FULL_COMPILE([input], [], [], [], [--no-line])
+AT_CHECK([grep 'define YYNSTATES  *$1' input.c], [], [ignore])
+AT_CHECK([grep 'typedef $2 yy_state_num' input.c], [], [ignore])
+AT_PARSER_CHECK([input])
+
+AT_BISON_OPTION_POPDEFS
+AT_CLEANUP])
+
+AT_TEST(  [256], [yytype_uint8])
+AT_TEST(  [257], [yytype_uint16])
+AT_TEST([65536], [yytype_uint16])
+AT_TEST([65537], [int])
+
+m4_popdef([AT_TEST])
+
+
+
+## ------------------------ ##
+## Many lookahead tokens.   ##
+## ------------------------ ##
+
 # AT_DATA_LOOKAHEAD_TOKENS_GRAMMAR(FILE-NAME, SIZE)
 # --------------------------------------------------
 # Create FILE-NAME, containing a self checking parser for a grammar
@@ -340,11 +377,6 @@ mv stdout $1
 AT_BISON_OPTION_POPDEFS
 ])
 
-
-## ------------------------ ##
-## Many lookahead tokens.   ##
-## ------------------------ ##
-
 AT_SETUP([Many lookahead tokens])
 
 AT_DATA_LOOKAHEAD_TOKENS_GRAMMAR([input.y], [1000])