The computation of nullable is broken: it doesn't handle empty

RHS's properly.
* tests/torture.at (GNU AWK Grammar): New.
* tests/sets.at (Nullable): New.
* src/nullable.c (set_nullable): Instead of blindly looping over
`ritems', loop over the rules, and then over their rhs's.
Work around Autotest bugs.
* src/warshall.c (bitmatrix_print): Don't use `+--+' as table
frame, because Autotest understand lines starting with a `+' as
traces from the shell.  Then, they are not processed properly.
Admittedly an Autotest bug, but we don't have time to wait for
Autotest to catch up.
* tests/regression.at (Broken Closure): Adjust to the new table
frames.
Move to...
* tests/sets.at: here.

tests/torture.at

@@ -114,3 +114,343 @@ AT_CHECK([input 900], 0, [], [ignore])
 AT_CHECK([input 10000], 1, [], [ignore])
 
 AT_CLEANUP
+
+
+## ----------------- ##
+## GNU AWK Grammar.  ##
+## ----------------- ##
+
+AT_SETUP([GNU AWK Grammar])
+
+# We have been careful to strip all the actions excepts the
+# mid-rule actions.  We rely on %expect to check that there are
+# indeed 65 SR conflicts.
+#
+# Bison was once wrong, due to an incorrect computation of nullable.
+# It reported 485 SR conflicts!
+
+AT_DATA([[input.y]],
+[[%expect 65
+
+%token FUNC_CALL NAME REGEXP
+%token ERROR
+%token YNUMBER YSTRING
+%token RELOP APPEND_OP
+%token ASSIGNOP MATCHOP NEWLINE CONCAT_OP
+%token LEX_BEGIN LEX_END LEX_IF LEX_ELSE LEX_RETURN LEX_DELETE
+%token LEX_WHILE LEX_DO LEX_FOR LEX_BREAK LEX_CONTINUE
+%token LEX_PRINT LEX_PRINTF LEX_NEXT LEX_EXIT LEX_FUNCTION
+%token LEX_GETLINE LEX_NEXTFILE
+%token LEX_IN
+%token LEX_AND LEX_OR INCREMENT DECREMENT
+%token LEX_BUILTIN LEX_LENGTH
+
+/* Lowest to highest */
+%right ASSIGNOP
+%right '?' ':'
+%left LEX_OR
+%left LEX_AND
+%left LEX_GETLINE
+%nonassoc LEX_IN
+%left FUNC_CALL LEX_BUILTIN LEX_LENGTH
+%nonassoc ','
+%nonassoc MATCHOP
+%nonassoc RELOP '<' '>' '|' APPEND_OP TWOWAYIO
+%left CONCAT_OP
+%left YSTRING YNUMBER
+%left '+' '-'
+%left '*' '/' '%'
+%right '!' UNARY
+%right '^'
+%left INCREMENT DECREMENT
+%left '$'
+%left '(' ')'
+%%
+
+start
+	: opt_nls program opt_nls
+	;
+
+program
+	: rule
+	| program rule
+	| error
+	| program error
+	| /* empty */
+	;
+
+rule
+	: LEX_BEGIN {} action
+	| LEX_END {}   action
+	| LEX_BEGIN statement_term
+	| LEX_END statement_term
+	| pattern action
+	| action
+	| pattern statement_term
+	| function_prologue function_body
+	;
+
+func_name
+	: NAME
+	| FUNC_CALL
+	| lex_builtin
+	;
+
+lex_builtin
+	: LEX_BUILTIN
+	| LEX_LENGTH
+	;
+
+function_prologue
+	: LEX_FUNCTION {} func_name '(' opt_param_list r_paren opt_nls
+	;
+
+function_body
+	: l_brace statements r_brace opt_semi opt_nls
+	| l_brace r_brace opt_semi opt_nls
+	;
+
+
+pattern
+	: exp
+	| exp ',' exp
+	;
+
+regexp
+	/*
+	 * In this rule, want_regexp tells yylex that the next thing
+	 * is a regexp so it should read up to the closing slash.
+	 */
+	: '/' {} REGEXP '/'
+	;
+
+action
+	: l_brace statements r_brace opt_semi opt_nls
+	| l_brace r_brace opt_semi opt_nls
+	;
+
+statements
+	: statement
+	| statements statement
+	| error
+	| statements error
+	;
+
+statement_term
+	: nls
+	| semi opt_nls
+	;
+
+statement
+	: semi opt_nls
+	| l_brace r_brace
+	| l_brace statements r_brace
+	| if_statement
+	| LEX_WHILE '(' exp r_paren opt_nls statement
+	| LEX_DO opt_nls statement LEX_WHILE '(' exp r_paren opt_nls
+	| LEX_FOR '(' NAME LEX_IN NAME r_paren opt_nls statement
+	| LEX_FOR '(' opt_exp semi opt_nls exp semi opt_nls opt_exp r_paren opt_nls statement
+	| LEX_FOR '(' opt_exp semi opt_nls semi opt_nls opt_exp r_paren opt_nls statement
+	| LEX_BREAK statement_term
+	| LEX_CONTINUE statement_term
+	| print '(' expression_list r_paren output_redir statement_term
+	| print opt_rexpression_list output_redir statement_term
+	| LEX_NEXT statement_term
+	| LEX_NEXTFILE statement_term
+	| LEX_EXIT opt_exp statement_term
+	| LEX_RETURN {} opt_exp statement_term
+	| LEX_DELETE NAME '[' expression_list ']' statement_term
+	| LEX_DELETE NAME  statement_term
+	| exp statement_term
+	;
+
+print
+	: LEX_PRINT
+	| LEX_PRINTF
+	;
+
+if_statement
+	: LEX_IF '(' exp r_paren opt_nls statement
+	| LEX_IF '(' exp r_paren opt_nls statement
+	     LEX_ELSE opt_nls statement
+	;
+
+nls
+	: NEWLINE
+	| nls NEWLINE
+	;
+
+opt_nls
+	: /* empty */
+	| nls
+	;
+
+input_redir
+	: /* empty */
+	| '<' simp_exp
+	;
+
+output_redir
+	: /* empty */
+	| '>' exp
+	| APPEND_OP exp
+	| '|' exp
+	| TWOWAYIO exp
+	;
+
+opt_param_list
+	: /* empty */
+	| param_list
+	;
+
+param_list
+	: NAME
+	| param_list comma NAME
+	| error
+	| param_list error
+	| param_list comma error
+	;
+
+/* optional expression, as in for loop */
+opt_exp
+	: /* empty */
+	| exp
+	;
+
+opt_rexpression_list
+	: /* empty */
+	| rexpression_list
+	;
+
+rexpression_list
+	: rexp
+	| rexpression_list comma rexp
+	| error
+	| rexpression_list error
+	| rexpression_list error rexp
+	| rexpression_list comma error
+	;
+
+opt_expression_list
+	: /* empty */
+	| expression_list
+	;
+
+expression_list
+	: exp
+	| expression_list comma exp
+	| error
+	| expression_list error
+	| expression_list error exp
+	| expression_list comma error
+	;
+
+/* Expressions, not including the comma operator.  */
+exp	: variable ASSIGNOP {} exp
+	| '(' expression_list r_paren LEX_IN NAME
+	| exp '|' LEX_GETLINE opt_variable
+	| exp TWOWAYIO LEX_GETLINE opt_variable
+	| LEX_GETLINE opt_variable input_redir
+	| exp LEX_AND exp
+	| exp LEX_OR exp
+	| exp MATCHOP exp
+	| regexp
+	| '!' regexp %prec UNARY
+	| exp LEX_IN NAME
+	| exp RELOP exp
+	| exp '<' exp
+	| exp '>' exp
+	| exp '?' exp ':' exp
+	| simp_exp
+	| exp simp_exp %prec CONCAT_OP
+	;
+
+rexp
+	: variable ASSIGNOP {} rexp
+	| rexp LEX_AND rexp
+	| rexp LEX_OR rexp
+	| LEX_GETLINE opt_variable input_redir
+	| regexp
+	| '!' regexp %prec UNARY
+	| rexp MATCHOP rexp
+	| rexp LEX_IN NAME
+	| rexp RELOP rexp
+	| rexp '?' rexp ':' rexp
+	| simp_exp
+	| rexp simp_exp %prec CONCAT_OP
+	;
+
+simp_exp
+	: non_post_simp_exp
+	/* Binary operators in order of decreasing precedence.  */
+	| simp_exp '^' simp_exp
+	| simp_exp '*' simp_exp
+	| simp_exp '/' simp_exp
+	| simp_exp '%' simp_exp
+	| simp_exp '+' simp_exp
+	| simp_exp '-' simp_exp
+	| variable INCREMENT
+	| variable DECREMENT
+	;
+
+non_post_simp_exp
+	: '!' simp_exp %prec UNARY
+	| '(' exp r_paren
+	| LEX_BUILTIN
+	  '(' opt_expression_list r_paren
+	| LEX_LENGTH '(' opt_expression_list r_paren
+	| LEX_LENGTH
+	| FUNC_CALL '(' opt_expression_list r_paren
+	| variable
+	| INCREMENT variable
+	| DECREMENT variable
+	| YNUMBER
+	| YSTRING
+	| '-' simp_exp    %prec UNARY
+	| '+' simp_exp    %prec UNARY
+	;
+
+opt_variable
+	: /* empty */
+	| variable
+	;
+
+variable
+	: NAME
+	| NAME '[' expression_list ']'
+	| '$' non_post_simp_exp
+	;
+
+l_brace
+	: '{' opt_nls
+	;
+
+r_brace
+	: '}' opt_nls
+	;
+
+r_paren
+	: ')'
+	;
+
+opt_semi
+	: /* empty */
+	| semi
+	;
+
+semi
+	: ';'
+	;
+
+comma	: ',' opt_nls
+	;
+
+%%
+]])
+
+# Pass plenty of options, to exercise plenty of code, even if we
+# don't actually check the output.  But SEGV is watching us, and
+# so might do dmalloc.
+AT_CHECK([[bison --verbose --defines input.y]])
+
+AT_CLEANUP