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[PATCH 01/12] grammar: introduce %empty
From: |
Akim Demaille |
Subject: |
[PATCH 01/12] grammar: introduce %empty |
Date: |
Sat, 16 Feb 2013 14:55:37 +0100 |
Provide a means to explicitly denote empty right-hand sides of rules:
instead of
exp: { ... }
allow
exp: %empty { ... }
Make sure that %empty is properly used.
With help from Joel E. Denny and Gabriel Rassoul.
http://lists.gnu.org/archive/html/bison-patches/2013-01/msg00142.html
* src/reader.h, src/reader.c (grammar_current_rule_empty_set): New.
* src/parse-gram.y (%empty): New token.
Use it.
* src/scan-gram.l (%empty): Scan it.
* src/reader.c (grammar_rule_check): Check that %empty is properly used.
* tests/actions.at (Invalid uses of %empty, Valid uses of %empty): New.
---
THANKS | 1 +
src/parse-gram.y | 3 +++
src/reader.c | 17 +++++++++++++++
src/reader.h | 2 ++
src/scan-gram.l | 1 +
src/symlist.c | 1 +
src/symlist.h | 4 ++++
tests/actions.at | 65 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
8 files changed, 94 insertions(+)
diff --git a/THANKS b/THANKS
index 59e591d..f30602c 100644
--- a/THANKS
+++ b/THANKS
@@ -44,6 +44,7 @@ Fabrice Bauzac address@hidden
Florian Krohm address@hidden
Frank Heckenbach address@hidden
Frans Englich address@hidden
+Gabriel Rassoul address@hidden
Georg Sauthoff address@hidden
George Neuner address@hidden
Gilles Espinasse address@hidden
diff --git a/src/parse-gram.y b/src/parse-gram.y
index e889eb5..7ab214a 100644
--- a/src/parse-gram.y
+++ b/src/parse-gram.y
@@ -605,6 +605,7 @@ rhses.1:
| rhses.1 ";"
;
+%token PERCENT_EMPTY "%empty";
rhs:
/* Nothing. */
{ grammar_current_rule_begin (current_lhs_symbol, current_lhs_location,
@@ -615,6 +616,8 @@ rhs:
{ grammar_current_rule_action_append ($2, @2, $3, false); }
| rhs "%?{...}"
{ grammar_current_rule_action_append ($2, @2, NULL, true); }
+| rhs "%empty"
+ { grammar_current_rule_empty_set (@2); }
| rhs "%prec" symbol
{ grammar_current_rule_prec_set ($3, @3); }
| rhs "%dprec" INT
diff --git a/src/reader.c b/src/reader.c
index 9ef993c..a83f11c 100644
--- a/src/reader.c
+++ b/src/reader.c
@@ -333,6 +333,12 @@ grammar_rule_check (const symbol_list *r)
}
}
+ /* Check that %empty => empty rule. */
+ if (r->percent_empty_loc.start.file
+ && r->next && r->next->content.sym)
+ complain (&r->percent_empty_loc, complaint,
+ _("%%empty on non-empty rule"));
+
/* See comments in grammar_current_rule_prec_set for how POSIX
mandates this complaint. It's only for identifiers, so skip
it for char literals and strings, which are always tokens. */
@@ -434,6 +440,17 @@ grammar_current_rule_prec_set (symbol *precsym, location
loc)
current_rule->ruleprec = precsym;
}
+/* Set %empty for the current rule. */
+
+void
+grammar_current_rule_empty_set (location loc)
+{
+ if (current_rule->percent_empty_loc.start.file)
+ complain (&loc, complaint, _("only one %s allowed per rule"), "%empty");
+ else
+ current_rule->percent_empty_loc = loc;
+}
+
/* Attach dynamic precedence DPREC to the current rule. */
void
diff --git a/src/reader.h b/src/reader.h
index c15544e..ba6ffe6 100644
--- a/src/reader.h
+++ b/src/reader.h
@@ -47,6 +47,8 @@ void grammar_current_rule_begin (symbol *lhs, location loc,
named_ref *lhs_named_ref);
void grammar_current_rule_end (location loc);
void grammar_midrule_action (void);
+/* Apply %empty to the current rule. */
+void grammar_current_rule_empty_set (location loc);
void grammar_current_rule_prec_set (symbol *precsym, location loc);
void grammar_current_rule_dprec_set (int dprec, location loc);
void grammar_current_rule_merge_set (uniqstr name, location loc);
diff --git a/src/scan-gram.l b/src/scan-gram.l
index 2ed6d2f..7ce3b4b 100644
--- a/src/scan-gram.l
+++ b/src/scan-gram.l
@@ -217,6 +217,7 @@ eqopt ([[:space:]]*=)?
"%defines" return PERCENT_DEFINES;
"%destructor" return PERCENT_DESTRUCTOR;
"%dprec" return PERCENT_DPREC;
+ "%empty" return PERCENT_EMPTY;
"%error-verbose" return PERCENT_ERROR_VERBOSE;
"%expect" return PERCENT_EXPECT;
"%expect-rr" return PERCENT_EXPECT_RR;
diff --git a/src/symlist.c b/src/symlist.c
index d43591a..005d808 100644
--- a/src/symlist.c
+++ b/src/symlist.c
@@ -44,6 +44,7 @@ symbol_list_sym_new (symbol *sym, location loc)
/* Members used for LHS only. */
res->ruleprec = NULL;
+ res->percent_empty_loc = empty_location;
code_props_none_init (&res->action_props);
res->dprec = 0;
res->merger = 0;
diff --git a/src/symlist.h b/src/symlist.h
index 657efac..9b0f117 100644
--- a/src/symlist.h
+++ b/src/symlist.h
@@ -78,6 +78,10 @@ typedef struct symbol_list
* each RHS are also stored here. */
code_props action_props;
+ /* The location of the first %empty for this rule, or \a
+ empty_location. */
+ location percent_empty_loc;
+
int dprec;
int merger;
location merger_declaration_location;
diff --git a/tests/actions.at b/tests/actions.at
index 9473f6e..473c79f 100644
--- a/tests/actions.at
+++ b/tests/actions.at
@@ -64,6 +64,71 @@ AT_PARSER_CHECK([./input], 0,
AT_CLEANUP
+## ------------------------ ##
+## Invalid uses of %empty. ##
+## ------------------------ ##
+
+AT_SETUP([Invalid uses of %empty])
+
+AT_DATA_GRAMMAR([[one.y]],
+[[%%
+exp:
+ %empty %empty {}
+;
+]])
+
+AT_BISON_CHECK([-fcaret one.y], [1], [],
+[[one.y:11.10-15: error: only one %empty allowed per rule
+ %empty %empty {}
+ ^^^^^^
+]])
+
+AT_DATA_GRAMMAR([[two.y]],
+[[%%
+exp:
+ 'a' %empty {}
+| %empty 'a' {}
+;
+]])
+
+AT_BISON_CHECK([-fcaret two.y], [1], [],
+[[two.y:11.7-12: error: %empty on non-empty rule
+ 'a' %empty {}
+ ^^^^^^
+two.y:12.3-8: error: %empty on non-empty rule
+ | %empty 'a' {}
+ ^^^^^^
+]])
+
+AT_CLEANUP
+
+## ---------------------- ##
+## Valid uses of %empty. ##
+## ---------------------- ##
+
+AT_SETUP([Valid uses of %empty])
+
+AT_BISON_OPTION_PUSHDEFS
+AT_DATA_GRAMMAR([[input.y]],
+[[
+%debug
+%code
+{
+]AT_YYERROR_DECLARE[
+]AT_YYLEX_DECLARE[
+}
+%%
+exp: %empty {}
+%%
+]AT_YYERROR_DEFINE[
+]AT_YYLEX_DEFINE[
+]AT_MAIN_DEFINE[
+]])
+
+AT_FULL_COMPILE([input])
+AT_PARSER_CHECK([./input])
+AT_BISON_OPTION_POPDEFS
+AT_CLEANUP
## ------------------ ##
## Initial location. ##
--
1.8.1.3
- Re: RFC: explicit empty right-hand side of a rule, (continued)
- Re: RFC: explicit empty right-hand side of a rule, Akim Demaille, 2013/02/03
- Re: RFC: explicit empty right-hand side of a rule, Joel E. Denny, 2013/02/03
- Re: RFC: explicit empty right-hand side of a rule, Akim Demaille, 2013/02/04
- Re: RFC: explicit empty right-hand side of a rule, Joel E. Denny, 2013/02/04
- Re: RFC: explicit empty right-hand side of a rule, Akim Demaille, 2013/02/05
- Re: RFC: explicit empty right-hand side of a rule, Joel E. Denny, 2013/02/05
- [PATCH 00/12] {master} explicit empty right-hand side of a rule, Akim Demaille, 2013/02/18
- Re: [PATCH 00/12] {master} explicit empty right-hand side of a rule, Akim Demaille, 2013/02/16
- Re: [PATCH 00/12] {master} explicit empty right-hand side of a rule, Akim Demaille, 2013/02/19
- [PATCH 02/12] parser: use %empty, Akim Demaille, 2013/02/18
- [PATCH 01/12] grammar: introduce %empty,
Akim Demaille <=
- Re: [PATCH 01/12] grammar: introduce %empty, Akim Demaille, 2013/02/18
- [PATCH 10/12] style: no longer use backquotes in messages, Akim Demaille, 2013/02/18
- [PATCH 08/12] doc: introduce %empty and -Wempty-rule, Akim Demaille, 2013/02/18
- Re: [PATCH 08/12] doc: introduce %empty and -Wempty-rule, Akim Demaille, 2013/02/16
- [PATCH 07/12] report: use %empty to denote empty rules, Akim Demaille, 2013/02/18
- [PATCH 09/12] doc: use %empty instead of /* empty */, Akim Demaille, 2013/02/18
- [PATCH 11/12] style: no longer use backquotes, Akim Demaille, 2013/02/18
- [PATCH 06/12] diagnostics: %empty enables -Wempty-rule, Akim Demaille, 2013/02/18
- [PATCH 05/12] -Wempty-rule: diagnose empty rules without %empty, Akim Demaille, 2013/02/18
- [PATCH 04/12] tests: use %empty, Akim Demaille, 2013/02/18