FYI: Both: Serious LALR bug

[Akim Demaille]

I'm still shocked that all the tests passed with such a bug in the
guts... And ashamed to have introduced it...

Index: ChangeLog
from  Akim Demaille  <address@hidden>
        Some actions of web2c.y are improperly triggered.
        Reported by Mike Castle.

        * src/lalr.c (traverse): s/F (i)[k] = F (j)[k]/F (j)[k] = F (i)[k]/.
        * tests/regression.at (Web2c): Rename as...
        (Web2c Report): this.
        (Web2c Actions): New.

Index: src/lalr.c
===================================================================
RCS file: /cvsroot/bison/bison/src/lalr.c,v
retrieving revision 1.16.2.21
diff -u -u -r1.16.2.21 lalr.c
--- src/lalr.c 10 Dec 2001 08:43:37 -0000 1.16.2.21
+++ src/lalr.c 22 Dec 2001 14:43:49 -0000
@@ -103,7 +103,7 @@
          break;
 
        for (k = 0; k < size; ++k)
-         F (i)[k] = F (j)[k];
+         F (j)[k] = F (i)[k];
       }
 }
 
Index: tests/regression.at
===================================================================
RCS file: /cvsroot/bison/bison/tests/regression.at,v
retrieving revision 1.1.2.23
diff -u -u -r1.1.2.23 regression.at
--- tests/regression.at 22 Dec 2001 14:41:15 -0000 1.1.2.23
+++ tests/regression.at 22 Dec 2001 14:43:49 -0000
@@ -614,16 +614,16 @@
 
 
 
-## ------- ##
-## Web2c.  ##
-## ------- ##
+## -------------- ##
+## Web2c Report.  ##
+## -------------- ##
 
 # The generation of the reduction was once wrong in Bison, and made it
 # miss some reductions.  In the following test case, the reduction on
 # `undef_id_tok' in state 1 was missing.  This is stripped down from
 # the actual web2c.y.
 
-AT_SETUP([Web2c])
+AT_SETUP([Web2c Report])
 
 AT_DATA([input.y],
 [[%token       undef_id_tok const_id_tok
@@ -713,6 +713,131 @@
     $          go to state 11
 state 11
     $default   accept
+]])
+
+AT_CLEANUP
+
+
+## --------------- ##
+## Web2c Actions.  ##
+## --------------- ##
+
+# The generation of the mapping `state -> action' was once wrong in
+# extremely specific situations.  web2c.y exhibits this situation.
+# Below is a stripped version of the grammar.  It looks like one can
+# simplify it further, but just don't: it is tuned to exhibit a bug,
+# which disapears when applying sane grammar transformations.
+#
+# It used to be wrong on yydefact only:
+#
+# static const short yydefact[] =
+#  {
+# -       2,     0,     1,     0,     0,     2,     3,     2,     5,     4,
+# +       2,     0,     1,     0,     0,     0,     3,     2,     5,     4,
+#         0,     0
+#  };
+#
+# but let's check all the tables.
+
+
+AT_SETUP([Web2c Actions])
+
+AT_DATA([input.y],
+[[%%
+statement:  struct_stat;
+struct_stat:  /* empty. */ | if else;
+if: "if" "const" "then" statement;
+else: "else" statement;
+%%
+]])
+
+AT_CHECK([bison -v input.y -o input.c])
+
+# Check only the tables.  We don't use --no-parser, because it is
+# still to be implemented in the experimental branch of Bison.
+AT_CHECK([[sed -n 's/  *$//;/^static const.*\[\] =/,/^}/p' input.c]], 0,
+[[static const char 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,     3,     4,     5,
+       6
+};
+static const short yyprhs[] =
+{
+       0,     0,     2,     3,     6,    11
+};
+static const short yyrhs[] =
+{
+       8,     0,     0,     9,    10,     0,     3,     4,     5,     7,
+       0,     6,     7,     0
+};
+static const short yyrline[] =
+{
+       0,     2,     3,     3,     4,     5
+};
+static const char *const yytname[] =
+{
+  "$", "error", "$undefined.", "\"if\"", "\"const\"", "\"then\"",
+  "\"else\"", "statement", "struct_stat", "if", "else", NULL
+};
+static const short yyr1[] =
+{
+       0,     7,     8,     8,     9,    10
+};
+static const short yyr2[] =
+{
+       0,     1,     0,     2,     4,     2
+};
+static const short yydefact[] =
+{
+       2,     0,     1,     0,     0,     2,     3,     2,     5,     4,
+       0,     0,     0
+};
+static const short yydefgoto[] =
+{
+       8,     2,     3,     6
+};
+static const short yypact[] =
+{
+      -2,    -1,-32768,    -4,     1,    -2,-32768,    -2,-32768,-32768,
+       4,     5,-32768
+};
+static const short yypgoto[] =
+{
+       0,-32768,-32768,-32768
+};
+static const short yytable[] =
+{
+      10,     1,     5,     4,    11,    12,     7,     9
+};
+static const short yycheck[] =
+{
+       0,     3,     6,     4,     0,     0,     5,     7
+};
 ]])
 
 AT_CLEANUP