+2006-10-31 Joel E. Denny <jdenny@ces.clemson.edu>
+
+ Disable unset/unused mid-rule value warnings by default, and recognize
+ --warnings=midrule-values to enable them. Discussed starting at
+ <http://lists.gnu.org/archive/html/help-bison/2006-10/msg00030.html>.
+ * NEWS (2.3a+): Mention.
+ * src/getargs.c, src/getargs.h (warnings_args, warnings_types, enum
+ warnings): Add entry for midrule-values subargument.
+ * src/reader.c (symbol_should_be_used): Don't return true just because
+ the value is a set/used mid-rule value unless
+ --warnings=midrule-values was specified.
+ * tests/input.at (Unused values, Unused values before symbol
+ declarations): Run tests with and without --warnings=midrule-values.
+
+ * src/reader.c (check_and_convert_grammar): Use symbol_list_free rather
+ than LIST_FREE directly.
+
2006-10-31 Joel E. Denny <jdenny@ces.clemson.edu>
Finish implementing --warnings=error, which should not be implied by
* The -g and --graph options now output graphs in Graphviz DOT format,
not VCG format.
+* Revised warning: unset or unused mid-rule values
+
+ Since Bison 2.2, Bison has warned about mid-rule values that are set but not
+ used within any of the actions of the parent rule. For example, Bison warns
+ about unused $2 in:
+
+ exp: '1' { $$ = 1; } '+' exp { $$ = $1 + $4; };
+
+ Now, Bison also warns about mid-rule values that are used but not set. For
+ example, Bison warns about unset $$ in the mid-rule action in:
+
+ exp: '1' { $1 = 1; } '+' exp { $$ = $2 + $4; };
+
+ However, Bison now disables both of these warnings by default since they
+ sometimes prove to be false alarms in existing grammars employing the Yacc
+ constructs $0 or $-N (where N is some positive integer).
+
+ To enable these warnings, specify the flag `--warnings=midrule-values' or
+ `-W', which is a synonym for `--warnings=all'.
+
* Bison now recognizes two separate kinds of default %destructor's and
%printer's:
{
/* In a series of synonyms, present the most meaningful first, so
that argmatch_valid be more readable. */
- "none - no warnings",
- "yacc - incompatibilities with POSIX YACC",
- "all - all of the above",
- "error - warnings are errors",
+ "none - no warnings",
+ "midrule-values - unset or unused midrule values",
+ "yacc - incompatibilities with POSIX YACC",
+ "all - all of the above",
+ "error - warnings are errors",
0
};
static const int warnings_types[] =
{
warnings_none,
+ warnings_midrule_values,
warnings_yacc,
warnings_all,
warnings_error
{
warnings_none = 0, /**< Issue no warnings. */
warnings_error = 1 << 0, /**< Warnings are treated as errors. */
- warnings_yacc = 1 << 1, /**< POSIXME. */
+ warnings_midrule_values = 1 << 1, /**< Unset or unused midrule values. */
+ warnings_yacc = 1 << 2, /**< POSIXME. */
warnings_all = ~warnings_error /**< All above warnings. */
};
/** What warnings are issued. */
/*----------------------------------------------------------------------.
-| A symbol should be used if it has a destructor, or if it is a |
-| mid-rule symbol (i.e., the generated LHS replacing a mid-rule |
-| action) that was assigned to, as in "exp: { $$ = 1; } { $$ = $1; }". |
+| A symbol should be used if either: |
+| 1. It has a destructor. |
+| 2. --warnings=midrule-values and the symbol is a mid-rule symbol |
+| (i.e., the generated LHS replacing a mid-rule action) that was |
+| assigned to or used, as in "exp: { $$ = 1; } { $$ = $1; }". |
`----------------------------------------------------------------------*/
static bool
symbol_should_be_used (symbol_list const *s)
{
- return (symbol_destructor_get (s->content.sym)
- || (s->midrule && s->midrule->used)
- || (s->midrule_parent_rule
- && symbol_list_n_get (s->midrule_parent_rule,
- s->midrule_parent_rhs_index)->used));
+ if (symbol_destructor_get (s->content.sym))
+ return true;
+ if (warnings_flag & warnings_midrule_values)
+ return ((s->midrule && s->midrule->used)
+ || (s->midrule_parent_rule
+ && symbol_list_n_get (s->midrule_parent_rule,
+ s->midrule_parent_rhs_index)->used));
+ return false;
}
/*----------------------------------------------------------------.
packgram ();
/* The grammar as a symbol_list is no longer needed. */
- LIST_FREE (symbol_list, grammar);
+ symbol_list_free (grammar);
}
%destructor { destroy ($$); } INT a b c d e f g h i j k l;]]])
-# AT_CHECK_UNUSED_VALUES(DECLARATIONS_AFTER)
-# --------------------------------------------
+# AT_CHECK_UNUSED_VALUES(DECLARATIONS_AFTER, CHECK_MIDRULE_VALUES)
+# ------------------------------------------------------------------
# Generate a grammar to test unused values,
# compile it, run it. If DECLARATIONS_AFTER
# is set, then the token, type, and destructor
# declarations are generated after the rules
-# rather than before.
+# rather than before. If CHECK_MIDRULE_VALUES
+# is set, then --warnings=midrule-values is
+# set.
m4_define([AT_CHECK_UNUSED_VALUES],
[AT_DATA([input.y],
_AT_UNUSED_VALUES_DECLARATIONS])
)
-AT_CHECK([bison input.y], [0], [],
+AT_CHECK([bison]m4_ifval($2, [ --warnings=midrule-values ])[ input.y], [0], [],
[[input.y:11.10-32: warning: unset value: $]$[
input.y:11.10-32: warning: unused value: $]1[
input.y:11.10-32: warning: unused value: $]3[
input.y:11.10-32: warning: unused value: $]5[
input.y:12.9: warning: empty rule for typed nonterminal, and no action
-input.y:13.14-19: warning: unset value: $$
+]]m4_ifval($2, [[[input.y:13.14-19: warning: unset value: $$
input.y:13.25-39: warning: unset value: $$
-input.y:13.10-59: warning: unset value: $]$[
+]]])[[input.y:13.10-59: warning: unset value: $]$[
input.y:13.10-59: warning: unused value: $]3[
input.y:13.10-59: warning: unused value: $]5[
-input.y:14.14-16: warning: unset value: $$
-input.y:14.10-47: warning: unset value: $]$[
+]]m4_ifval($2, [[[input.y:14.14-16: warning: unset value: $$
+]]])[[input.y:14.10-47: warning: unset value: $]$[
input.y:14.10-47: warning: unused value: $]3[
input.y:14.10-47: warning: unused value: $]5[
input.y:15.10-36: warning: unset value: $]$[
input.y:15.10-36: warning: unused value: $]5[
input.y:17.10-58: warning: unset value: $]$[
input.y:17.10-58: warning: unused value: $]1[
-input.y:17.10-58: warning: unused value: $]2[
-input.y:17.10-58: warning: unused value: $]3[
-input.y:17.10-58: warning: unused value: $]4[
-input.y:17.10-58: warning: unused value: $]5[
+]]m4_ifval($2, [[[input.y:17.10-58: warning: unused value: $]2[
+]]])[[input.y:17.10-58: warning: unused value: $]3[
+]]m4_ifval($2, [[[input.y:17.10-58: warning: unused value: $]4[
+]]])[[input.y:17.10-58: warning: unused value: $]5[
input.y:18.10-72: warning: unset value: $]$[
input.y:18.10-72: warning: unused value: $]1[
input.y:18.10-72: warning: unused value: $]3[
-input.y:18.10-72: warning: unused value: $]4[
-input.y:18.10-72: warning: unused value: $]5[
-input.y:20.10-55: warning: unused value: $]3[
-input.y:21.10-68: warning: unset value: $]$[
+]]m4_ifval($2, [[[input.y:18.10-72: warning: unused value: $]4[
+]]])[[input.y:18.10-72: warning: unused value: $]5[
+]]m4_ifval($2, [[[input.y:20.10-55: warning: unused value: $]3[
+]]])[[input.y:21.10-68: warning: unset value: $]$[
input.y:21.10-68: warning: unused value: $]1[
input.y:21.10-68: warning: unused value: $]2[
-input.y:21.10-68: warning: unused value: $]4[
-]])])
+]]m4_ifval($2, [[[input.y:21.10-68: warning: unused value: $]4[
+]]]))])
## --------------- ##
AT_SETUP([Unused values])
AT_CHECK_UNUSED_VALUES
+AT_CHECK_UNUSED_VALUES(, [1])
AT_CLEANUP
AT_SETUP([Unused values before symbol declarations])
AT_CHECK_UNUSED_VALUES([1])
+AT_CHECK_UNUSED_VALUES([1], [1])
AT_CLEANUP
projects / bison.git / commitdiff
