- `midrule-values' unset or unused midrule values\n\
- `yacc' incompatibilities with POSIX Yacc\n\
- `conflicts-sr' S/R conflicts (enabled by default)\n\
- `conflicts-rr' R/R conflicts (enabled by default)\n\
- `deprecated' obsolete constructs\n\
- `precedence' useless precedence and associativity\n\
- `other' all other warnings (enabled by default)\n\
- `all' all the warnings\n\
- `no-CATEGORY' turn off warnings in CATEGORY\n\
- `none' turn off all the warnings\n\
- `error[=CATEGORY]' treat warnings as errors\n\
+ 'midrule-values' unset or unused midrule values\n\
+ 'yacc' incompatibilities with POSIX Yacc\n\
+ 'conflicts-sr' S/R conflicts (enabled by default)\n\
+ 'conflicts-rr' R/R conflicts (enabled by default)\n\
+ 'deprecated' obsolete constructs\n\
+ 'empty-rule' empty rules without %empty\n\
+ 'precedence' useless precedence and associativity\n\
+ 'other' all other warnings (enabled by default)\n\
+ 'all' all the warnings except 'yacc'\n\
+ 'no-CATEGORY' turn off warnings in CATEGORY\n\
+ 'none' turn off all the warnings\n\
+ 'error[=CATEGORY]' treat warnings as errors\n\