Enable declaration of default %printer/%destructor. Make the parser

use these for all user-declared grammar symbols for which the user does
not declare a specific %printer/%destructor.  Thus, the parser uses it
for token 0 if the user declares it but not if Bison generates it as
$end.  Discussed starting at
<http://lists.gnu.org/archive/html/bison-patches/2006-02/msg00064.html>,
<http://lists.gnu.org/archive/html/bison-patches/2006-06/msg00091.html>,
and
<http://lists.gnu.org/archive/html/bison-patches/2006-07/msg00019.html>.
* NEWS (2.3+): Mention.
* doc/bison.texinfo (Actions in Mid-Rule): It's no longer impossible to
declare a %destructor for a mid-rule's semantic value.  It's just
impossible to declare one specific to it.
(Freeing Discarded Symbols): Mention that @$ can be used in %destructor
code.  Describe default %destructor form.
* src/parse-gram.y (grammar_declaration): Parse default
%printer/%destructor declarations.
* src/output.c (symbol_destructors_output): Use symbol_destructor_get
and symbol_destructor_location_get rather than accessing the destructor
and destructor_location members of struct symbol.
(symbol_printers_output): Likewise but for %printer's.
* src/reader.c (symbol_should_be_used): Likewise but for %destructor's
again.
* src/symtab.c (default_destructor, default_destructor_location,
default_printer, default_printer_location): New static global
variables to record the default %destructor and %printer.
(symbol_destructor_get, symbol_destructor_location_get,
symbol_printer_get, symbol_printer_location_get): New functions to
compute the appropriate %destructor and %printer for a symbol.
(default_destructor_set, default_printer_set): New functions to set the
default %destructor and %printer.
* src/symtab.h: Prototype all those new functions.
* tests/actions.at (Default %printer and %destructor): New test to
check that the right %printer and %destructor are called, that they're
not called for $end, and that $$ and @$ work correctly.
(Default %printer and %destructor for user-declared end token): New
test to check that the default %printer and %destructor are called for
a user-declared end token.
* tests/input.at (Default %printer and %destructor redeclared, Unused
values with default %destructor): New tests to check related grammar
warnings and errors.

tests/actions.at

@@ -575,3 +575,202 @@ AT_CHECK_PRINTER_AND_DESTRUCTOR([%defines %skeleton "lalr1.cc"], [with union])
 
 AT_CHECK_PRINTER_AND_DESTRUCTOR([%glr-parser])
 AT_CHECK_PRINTER_AND_DESTRUCTOR([%glr-parser], [with union])
+
+
+
+
+
+## --------------------------------- ##
+## Default %printer and %destructor. ##
+## --------------------------------- ##
+
+# Check that the right %printer and %destructor are called, that they're not
+# called for $end, and that $$ and @$ work correctly.
+
+AT_SETUP([Default %printer and %destructor])
+
+AT_DATA_GRAMMAR([[input.y]],
+[[%error-verbose
+%debug
+%locations
+%initial-action {
+  @$.first_line = @$.last_line = 1;
+  @$.first_column = @$.last_column = 1;
+}
+
+%{
+# include <stdio.h>
+# include <stdlib.h>
+  static void yyerror (const char *msg);
+  static int yylex (void);
+# define USE(SYM)
+%}
+
+%printer {
+  fprintf (yyoutput, "Default printer for '%c' @ %d", $$, @$.first_column);
+}
+%destructor {
+  fprintf (stdout, "Default destructor for '%c' @ %d.\n", $$, @$.first_column);
+}
+
+%printer {
+  fprintf (yyoutput, "'b'/'c' printer for '%c' @ %d", $$, @$.first_column);
+} 'b' 'c'
+%destructor {
+  fprintf (stdout, "'b'/'c' destructor for '%c' @ %d.\n", $$, @$.first_column);
+} 'b' 'c'
+
+%%
+
+start: 'a' 'b' 'c' 'd' 'e' { $$ = 'S'; USE(($1, $2, $3, $4, $5)); } ;
+
+%%
+
+static int
+yylex (void)
+{
+  static const char *input = "abcd";
+  static int column = 1;
+  yylval = *input++;
+  yylloc.first_line = yylloc.last_line = 1;
+  yylloc.first_column = yylloc.last_column = column++;
+  return yylval;
+}
+
+static void
+yyerror (const char *msg)
+{
+  fprintf (stderr, "%s\n", msg);
+}
+
+int
+main (void)
+{
+  yydebug = 1;
+  return yyparse ();
+}
+]])
+
+AT_CHECK([bison -o input.c input.y])
+AT_COMPILE([input])
+AT_PARSER_CHECK([./input], 1,
+[[Default destructor for 'd' @ 4.
+'b'/'c' destructor for 'c' @ 3.
+'b'/'c' destructor for 'b' @ 2.
+Default destructor for 'a' @ 1.
+]],
+[[Starting parse
+Entering state 0
+Reading a token: Next token is token 'a' (1.1-1.1: Default printer for 'a' @ 1)
+Shifting token 'a' (1.1-1.1: Default printer for 'a' @ 1)
+Entering state 1
+Reading a token: Next token is token 'b' (1.2-1.2: 'b'/'c' printer for 'b' @ 2)
+Shifting token 'b' (1.2-1.2: 'b'/'c' printer for 'b' @ 2)
+Entering state 3
+Reading a token: Next token is token 'c' (1.3-1.3: 'b'/'c' printer for 'c' @ 3)
+Shifting token 'c' (1.3-1.3: 'b'/'c' printer for 'c' @ 3)
+Entering state 5
+Reading a token: Next token is token 'd' (1.4-1.4: Default printer for 'd' @ 4)
+Shifting token 'd' (1.4-1.4: Default printer for 'd' @ 4)
+Entering state 6
+Reading a token: Now at end of input.
+syntax error, unexpected $end, expecting 'e'
+Error: popping token 'd' (1.4-1.4: Default printer for 'd' @ 4)
+Stack now 0 1 3 5
+Error: popping token 'c' (1.3-1.3: 'b'/'c' printer for 'c' @ 3)
+Stack now 0 1 3
+Error: popping token 'b' (1.2-1.2: 'b'/'c' printer for 'b' @ 2)
+Stack now 0 1
+Error: popping token 'a' (1.1-1.1: Default printer for 'a' @ 1)
+Stack now 0
+Cleanup: discarding lookahead token $end (1.5-1.5: )
+Stack now 0
+]])
+
+AT_CLEANUP
+
+
+
+
+
+## ------------------------------------------------------------- ##
+## Default %printer and %destructor for user-declared end token. ##
+## ------------------------------------------------------------- ##
+
+AT_SETUP([Default %printer and %destructor for user-declared end token])
+
+AT_DATA_GRAMMAR([[input.y]],
+[[%error-verbose
+%debug
+%locations
+%initial-action {
+  @$.first_line = @$.last_line = 1;
+  @$.first_column = @$.last_column = 1;
+}
+
+%{
+# include <stdio.h>
+# include <stdlib.h>
+  static void yyerror (const char *msg);
+  static int yylex (void);
+# define USE(SYM)
+%}
+
+%token END 0
+%printer {
+  fprintf (yyoutput, "Default printer for '%c' @ %d", $$, @$.first_column);
+}
+%destructor {
+  fprintf (stdout, "Default destructor for '%c' @ %d.\n", $$, @$.first_column);
+}
+
+%%
+
+start: { $$ = 'S'; } ;
+
+%%
+
+static int
+yylex (void)
+{
+  yylval = 'E';
+  yylloc.first_line = yylloc.last_line = 1;
+  yylloc.first_column = yylloc.last_column = 1;
+  return 0;
+}
+
+static void
+yyerror (const char *msg)
+{
+  fprintf (stderr, "%s\n", msg);
+}
+
+int
+main (void)
+{
+  yydebug = 1;
+  return yyparse ();
+}
+]])
+
+AT_CHECK([bison -o input.c input.y])
+AT_COMPILE([input])
+AT_PARSER_CHECK([./input], 0,
+[[Default destructor for 'E' @ 1.
+Default destructor for 'S' @ 1.
+]],
+[[Starting parse
+Entering state 0
+Reducing stack by rule 1 (line 37):
+-> $$ = nterm start (1.1-1.1: Default printer for 'S' @ 1)
+Stack now 0
+Entering state 1
+Reading a token: Now at end of input.
+Shifting token END (1.1-1.1: Default printer for 'E' @ 1)
+Entering state 2
+Stack now 0 1 2
+Cleanup: popping token END (1.1-1.1: Default printer for 'E' @ 1)
+Cleanup: popping nterm start (1.1-1.1: Default printer for 'S' @ 1)
+]])
+
+AT_CLEANUP

tests/input.at

@@ -168,6 +168,65 @@ AT_CHECK_UNUSED_VALUES([1])
 AT_CLEANUP
 
 
+## --------------------------------------------- ##
+## Default %printer and %destructor redeclared.  ##
+## --------------------------------------------- ##
+
+AT_SETUP([Default %printer and %destructor redeclared])
+
+AT_DATA([[input.y]],
+[[%destructor { destroy ($$); }
+%printer { destroy ($$); }
+
+%destructor { destroy ($$); }
+%printer { destroy ($$); }
+
+%%
+
+start: ;
+
+%destructor { destroy ($$); };
+%printer { destroy ($$); };
+]])
+
+AT_CHECK([bison input.y], [1], [],
+[[input.y:4.13-29: redeclaration for default %destructor
+input.y:1.13-29: previous declaration
+input.y:5.10-26: redeclaration for default %printer
+input.y:2.10-26: previous declaration
+input.y:11.13-29: redeclaration for default %destructor
+input.y:4.13-29: previous declaration
+input.y:12.10-26: redeclaration for default %printer
+input.y:5.10-26: previous declaration
+]])
+
+AT_CLEANUP
+
+
+## ---------------------------------------- ##
+## Unused values with default %destructor.  ##
+## ---------------------------------------- ##
+
+AT_SETUP([Unused values with default %destructor])
+
+AT_DATA([[input.y]],
+[[%destructor { destroy ($$); }
+
+%%
+
+start: end end { $1; } ;
+end: { }  ;
+]])
+
+AT_CHECK([bison input.y], [0], [],
+[[input.y:5.8-22: warning: unset value: $$
+input.y:5.8-22: warning: unused value: $2
+input.y:6.6-8: warning: unset value: $$
+]])
+
+AT_CLEANUP
+
+
 ## ---------------------- ##
 ## Incompatible Aliases.  ##
 ## ---------------------- ##