tests: check symbol/token renumbering

In some extreme situations, with lots of useless tokens, Bison was
numbering them incorrectly, which resulted in a broken grammar.
<https://lists.gnu.org/r/bison-patches/2021-03/msg00001.html>
commit a774839ca873d1082f79ba3c4eecc1e242a28ce1.

* tests/regression.at (Useless Tokens): New.

1 files changed, 297 insertions, 1 deletions

diff --git a/tests/regression.at b/tests/regression.at
index a64da9ab..1a796a92 100644
--- a/tests/regression.at
+++ b/tests/regression.at
@@ -674,7 +674,7 @@ else: "else" statement;
 AT_BISON_CHECK([-v -o input.c input.y])
 
 # Check only the tables.
-[sed -n 's/  *$//;/^static const.*\[\] =/,/^}/p' input.c >tables.c]
+[sed -n 's/  *$//;/^static const.*\[\] =/,/^}/p;/#define YY.*NINF/p' input.c >tables.c]
 
 AT_CHECK([[cat tables.c]], 0,
 [[static const yytype_int8 yytranslate[] =
@@ -717,6 +717,8 @@ static const char *const yytname[] =
   "\"then\"", "\"else\"", "$accept", "statement", "struct_stat", "if",
   "else", YY_NULLPTR
 };
+#define YYPACT_NINF (-8)
+#define YYTABLE_NINF (-1)
 static const yytype_int8 yypact[] =
 {
       -2,    -1,     4,    -8,     0,     2,    -8,    -2,    -8,    -2,
@@ -761,6 +763,300 @@ static const yytype_int8 yyr2[] =
 AT_CLEANUP
 
 
+## ---------------- ##
+## Useless Tokens.  ##
+## ---------------- ##
+
+# In some extreme situations, with lots of useless tokens, Bison was
+# numbering them incorrectly, which resulted in a broken grammar.
+# <https://lists.gnu.org/r/bison-patches/2021-03/msg00001.html>
+# commit a774839ca873d1082f79ba3c4eecc1e242a28ce1.
+#
+# To track this failure, compare the tables between an incorrect
+# version of Bison (e.g., 3.7.5), and a correct one:
+#
+# LC_ALL=C /usr/local/stow/bison-3.7.5/bin/bison input.y -o old.c &&
+# LC_ALL=C                                 bison input.y -o new.c &&
+# sed -n 's/  *$//;/^static const.*\[\] =/,/^}/p' old.c >old.tables &&
+# sed -n 's/  *$//;/^static const.*\[\] =/,/^}/p' new.c >new.tables &&
+# diff old.tables new.tables
+#
+# The following Ruby script normalizes token and nterm names.
+#
+# #! /usr/bin/env ruby
+#
+# require 'strscan'
+#
+# tokens = {}
+# nterms = {}
+#
+# ARGV.each do |file|
+#   s = StringScanner.new File.read(file)
+#   while !s.eos?
+#     $stdout <<
+#       case
+#       when s.scan(/%\w+/)
+#         s.matched
+#       when s.scan(/[A-Z_0-9]+/)
+#         tokens[s.matched] ||= 'T%02d' % tokens.size
+#       when s.scan(/[a-z_0-9]+/)
+#         nterms[s.matched] ||= 'n%02d' % nterms.size
+#       when s.scan(/.|\n/)
+#         s.matched
+#       else
+#         raise "error: #{s.rest}"
+#       end
+#   end
+# end
+
+AT_SETUP([Useless Tokens])
+
+AT_DATA([input.y],
+[[%token
+  T00 T01 T02 T03 T04 T05 T06 T07 T08 T09 T10 T11 T12 T13 T14 T15 T16
+  T17 T18 T19 T20 T21 T22 T23 T24 T25 T26 T27 T28 T29 T30 T31 T32 T33
+  T34 T35 T36 T37 T38 T39 T40 T41 T42 T43 T44 T45 T46 T47 T48 T49 T50
+  T51 T52 T53 T54 T55 T56 T57 T58 T59 T60 T61 T62 T63 T64 T65 T66 T67
+  T68 T69 T70 T71 T72 T73 T74 T75 T76 T77 T78 T79 T80 T81 T82 T83 T84
+  T85 T86 T87 T88 T89 T90
+
+%%
+
+n00: T00 n01;
+n01: T77 T88 n02 T89;
+n02: n03 n02 | %empty;
+n03: T16 T88 n04 T89 | T79 T88 n05 T89 | T78 T88 n06 T89 | T81 T88 n07 T89 | T82 T88 n05 T89 | T83 T88 n05 T89 | T84 T88 n05 T89 | T80 T88 n08 T89 | n09;
+n04: n10 n04 | %empty;
+n05: T58 | T61;
+n06: n10
+n07: n05 | n11;
+n08: n12;
+n09: T30 T88 n05 T89;
+n11: n13 n11 | %empty;
+n13: T85 T88 n05 T89 | T86 T88 n08 T89;
+n10: n05;
+n14: %empty;
+n15: n16 T90 n15;
+n16: n17;
+n18: T58;
+n17: T07 T88 n19 T89;
+n19: n20;
+n20: n21 n20;
+n21: T13 T88 n22 T89;
+n22: n23;
+n24: n25;
+n25: n26 T90 n25 | n27 T90 n25;
+n26: n28;
+n28: T58;
+n29: n30 T90 n29;
+n30: T02 T88 n05 T89;
+n31: T04 T88 n32 T89;
+n33: n32;
+n32: n27 T90 n32;
+n27: T03 T88 n34 T89;
+n35: n36;
+n36: T05 T88 n34 T89 | n36 T06 T88 n34 T89;
+n34: n29 n33 n37;
+n37: T16 T88 n38 T89 T90;
+n38: n10 n38;
+n39: n05 | T58 T88 n05 T89;
+n40: n39;
+n41: n40 n41;
+n42: T48;
+n43: n42;
+n44: T59;
+n45: n44;
+n23: T59;
+n46: T60;
+n47: T60;
+n48: n05;
+n49: n05;
+n50: n49;
+n51: n49;
+n52: n05;
+n12: n05 n12 | %empty;
+n53: n05;
+n54: n05;
+n55: T15 T88 n05 T89;
+n56: T58;
+n57: n56;
+n58: T58;
+n59: T13 T88 n22 T89;
+n60: T75 T88 n22 T89;
+n61: T18 T88 n05 T89;
+n62: T76 T88 n46 T89;
+n63: n05 n63;
+n64: T14 T88 n22 T89;
+n65: T10 T88 n42 T89;
+n66: n05 n66;
+n67: T08 T88 n05 T89;
+n68: T11 T88 n42 T89;
+n69: T17 T88 n05 T89;
+n70: n71 n70;
+n71: T16 T88 n72 T89;
+n72: n10 n72;
+n73: T24 T88 n48 T89;
+n74: T12 T88 n05 T89;
+n75: T09 T88 n05 T89;
+n76: n05 n76;
+n77: T64 T88 n78 T89;
+n78: n79 n78;
+n79: T66 T88 n05 n40 T89;
+n80: n05 n80;
+n81: n82 n81;
+n82: T69 T88 n22 T89;
+n83: T47 T88 n05 T89;
+n84: T46 T88 T89;
+]])
+
+AT_BISON_CHECK([-Wno-other -o input.c input.y])
+
+# Check only the tables.
+[sed -n 's/  *$//;/^static const.*\[\] =/,/^}/p;/#define YY.*NINF/p' input.c >tables.c]
+
+AT_CHECK([[cat tables.c]], 0,
+[[static const yytype_int8 yytranslate[] =
+{
+       0,     2,     2,     2,     2,     2,     2,     2,     2,     2,
+       2,     2,     2,     2,     2,     2,     2,     2,     2,     2,
+       2,     2,     2,     2,     2,     2,     2,     2,     2,     2,
+       2,     2,     2,     2,     2,     2,     2,     2,     2,     2,
+       2,     2,     2,     2,     2,     2,     2,     2,     2,     2,
+       2,     2,     2,     2,     2,     2,     2,     2,     2,     2,
+       2,     2,     2,     2,     2,     2,     2,     2,     2,     2,
+       2,     2,     2,     2,     2,     2,     2,     2,     2,     2,
+       2,     2,     2,     2,     2,     2,     2,     2,     2,     2,
+       2,     2,     2,     2,     2,     2,     2,     2,     2,     2,
+       2,     2,     2,     2,     2,     2,     2,     2,     2,     2,
+       2,     2,     2,     2,     2,     2,     2,     2,     2,     2,
+       2,     2,     2,     2,     2,     2,     2,     2,     2,     2,
+       2,     2,     2,     2,     2,     2,     2,     2,     2,     2,
+       2,     2,     2,     2,     2,     2,     2,     2,     2,     2,
+       2,     2,     2,     2,     2,     2,     2,     2,     2,     2,
+       2,     2,     2,     2,     2,     2,     2,     2,     2,     2,
+       2,     2,     2,     2,     2,     2,     2,     2,     2,     2,
+       2,     2,     2,     2,     2,     2,     2,     2,     2,     2,
+       2,     2,     2,     2,     2,     2,     2,     2,     2,     2,
+       2,     2,     2,     2,     2,     2,     2,     2,     2,     2,
+       2,     2,     2,     2,     2,     2,     2,     2,     2,     2,
+       2,     2,     2,     2,     2,     2,     2,     2,     2,     2,
+       2,     2,     2,     2,     2,     2,     2,     2,     2,     2,
+       2,     2,     2,     2,     2,     2,     2,     2,     2,     2,
+       2,     2,     2,     2,     2,     2,     1,     2,     3,     4,
+       5,     6,     7,     8,     9,    10,    11,    12,    13,    14,
+      15,    16,    17,    18,    19,    20,    21,    22,    23,    24,
+      25,    26,    27,    28,    29,    30,    31,    32,    33,    34,
+      35,    36,    37,    38,    39,    40,    41,    42,    43,    44,
+      45,    46,    47,    48,    49,    50,    51,    52,    53,    54,
+      55,    56,    57,    58,    59,    60,    61,    62,    63,    64,
+      65,    66,    67,    68,    69,    70,    71,    72,    73,    74,
+      75,    76,    77,    78,    79,    80,    81,    82,    83,    84,
+      85,    86,    87,    88,    89,    90,    91,    92,    93
+};
+static const yytype_int8 yyrline[] =
+{
+       0,    11,    11,    12,    13,    13,    14,    14,    14,    14,
+      14,    14,    14,    14,    14,    15,    15,    16,    16,    17,
+      18,    18,    19,    20,    21,    21,    22,    22,    23,    63,
+      63
+};
+static const char *const yytname[] =
+{
+  "\"end of file\"", "error", "\"invalid token\"", "T00", "T01", "T02",
+  "T03", "T04", "T05", "T06", "T07", "T08", "T09", "T10", "T11", "T12",
+  "T13", "T14", "T15", "T16", "T17", "T18", "T19", "T20", "T21", "T22",
+  "T23", "T24", "T25", "T26", "T27", "T28", "T29", "T30", "T31", "T32",
+  "T33", "T34", "T35", "T36", "T37", "T38", "T39", "T40", "T41", "T42",
+  "T43", "T44", "T45", "T46", "T47", "T48", "T49", "T50", "T51", "T52",
+  "T53", "T54", "T55", "T56", "T57", "T58", "T59", "T60", "T61", "T62",
+  "T63", "T64", "T65", "T66", "T67", "T68", "T69", "T70", "T71", "T72",
+  "T73", "T74", "T75", "T76", "T77", "T78", "T79", "T80", "T81", "T82",
+  "T83", "T84", "T85", "T86", "T87", "T88", "T89", "T90", "$accept", "n00",
+  "n01", "n02", "n03", "n04", "n05", "n06", "n07", "n08", "n09", "n11",
+  "n13", "n10", "n12", YY_NULLPTR
+};
+#define YYPACT_NINF (-78)
+#define YYTABLE_NINF (-1)
+static const yytype_int8 yypact[] =
+{
+      -2,   -77,    11,   -73,   -78,   -78,   -19,   -71,   -69,   -68,
+     -67,   -66,   -65,   -64,   -63,   -62,   -61,   -19,   -78,   -49,
+     -49,   -49,   -49,   -49,   -51,   -49,   -49,   -49,   -78,   -78,
+     -78,   -78,   -60,   -78,   -49,   -59,   -58,   -78,   -57,   -49,
+     -56,   -78,   -52,   -48,   -78,   -50,   -78,   -72,   -47,   -46,
+     -45,   -78,   -78,   -78,   -78,   -78,   -78,   -78,   -49,   -49,
+     -78,   -78,   -78,   -78,   -78,   -44,   -43,   -78,   -78
+};
+static const yytype_int8 yydefact[] =
+{
+       0,     0,     0,     0,     2,     1,     5,     0,     0,     0,
+       0,     0,     0,     0,     0,     0,     0,     5,    14,    16,
+       0,     0,     0,    30,    25,     0,     0,     0,     3,     4,
+      17,    18,     0,    28,    16,     0,     0,    19,     0,    30,
+       0,    22,     0,     0,    20,     0,    21,    25,     0,     0,
+       0,     6,    15,    23,     8,     7,    29,    13,     0,    30,
+       9,    24,    10,    11,    12,     0,     0,    26,    27
+};
+static const yytype_int8 yypgoto[] =
+{
+     -78,   -78,   -78,     2,   -78,    -4,   -18,   -78,   -78,   -15,
+     -78,     3,   -78,    30,    13
+};
+static const yytype_int8 yydefgoto[] =
+{
+       0,     2,     4,    16,    17,    32,    33,    36,    45,    40,
+      18,    46,    47,    34,    41
+};
+static const yytype_int8 yytable[] =
+{
+       7,     1,    35,     3,    38,    39,    44,    48,    49,    50,
+      30,     5,    30,    31,     8,    31,    42,    43,     6,    29,
+      19,    39,    20,    21,    22,    23,    24,    25,    26,    27,
+      52,    28,    51,    53,    54,    55,    57,    42,    43,    58,
+      65,    39,    60,    59,    66,    62,    63,    64,    67,    68,
+      61,    37,    56,     0,     0,     0,     0,     0,     0,     0,
+       0,     0,     9,    10,    11,    12,    13,    14,    15
+};
+static const yytype_int8 yycheck[] =
+{
+      19,     3,    20,    80,    22,    23,    24,    25,    26,    27,
+      61,     0,    61,    64,    33,    64,    88,    89,    91,    17,
+      91,    39,    91,    91,    91,    91,    91,    91,    91,    91,
+      34,    92,    92,    92,    92,    92,    92,    88,    89,    91,
+      58,    59,    92,    91,    59,    92,    92,    92,    92,    92,
+      47,    21,    39,    -1,    -1,    -1,    -1,    -1,    -1,    -1,
+      -1,    -1,    81,    82,    83,    84,    85,    86,    87
+};
+static const yytype_int8 yystos[] =
+{
+       0,     3,    95,    80,    96,     0,    91,    19,    33,    81,
+      82,    83,    84,    85,    86,    87,    97,    98,   104,    91,
+      91,    91,    91,    91,    91,    91,    91,    91,    92,    97,
+      61,    64,    99,   100,   107,   100,   101,   107,   100,   100,
+     103,   108,    88,    89,   100,   102,   105,   106,   100,   100,
+     100,    92,    99,    92,    92,    92,   108,    92,    91,    91,
+      92,   105,    92,    92,    92,   100,   103,    92,    92
+};
+static const yytype_int8 yyr1[] =
+{
+       0,    94,    95,    96,    97,    97,    98,    98,    98,    98,
+      98,    98,    98,    98,    98,    99,    99,   100,   100,   101,
+     102,   102,   103,   104,   105,   105,   106,   106,   107,   108,
+     108
+};
+static const yytype_int8 yyr2[] =
+{
+       0,     2,     2,     4,     2,     0,     4,     4,     4,     4,
+       4,     4,     4,     4,     1,     2,     0,     1,     1,     1,
+       1,     1,     1,     4,     2,     0,     4,     4,     1,     2,
+       0
+};
+]])
+
+AT_CLEANUP
+
+
+
 ## ------------------------- ##
 ## yycheck Bound Violation.  ##
 ## ------------------------- ##