Typed right-hand side symbols whose value are not used are reported.
For instance:
- exp: exp "?" exp ":" exp { $$ = $1 ? $1 : $3; }
+ exp: exp "?" exp ":" exp { $1 ? $1 : $3; }
| exp "+" exp
;
- will trigger a warning about $5 of the first rule, and $3 in the
- second ($1 is copied to $$ by the default rule). This example
- most likely contains two errors, and should be rewritten as:
+ will trigger a warning about $$ and $5 in the first rule, and $3 in
+ the second ($1 is copied to $$ by the default rule). This example
+ most likely contains three errors, and should be rewritten as:
exp: exp "?" exp ":" exp { $$ = $1 ? $3 : $5; }
| exp "+" exp { $$ = $1 + $3; }
However, if the original actions were really intended, the warnings
can be suppressed by letting Bison believe the values are used, e.g.:
- exp: exp "?" exp ":" exp { $$ = $1 ? $1 : $3; (void) $5; }
+ exp: exp "?" exp ":" exp { $1 ? $1 : $3; (void) ($$, $5); }
| exp "+" exp { $$ = $1; (void) $3; }
;