+These warnings are not enabled by default since they sometimes prove to
+be false alarms in existing grammars employing the Yacc constructs
+@code{$0} or @code{$-@var{n}} (where @var{n} is some positive integer).
+
+@item yacc
+Incompatibilities with POSIX Yacc.
+
+@item conflicts-sr
+@itemx conflicts-rr
+S/R and R/R conflicts. These warnings are enabled by default. However, if
+the @code{%expect} or @code{%expect-rr} directive is specified, an
+unexpected number of conflicts is an error, and an expected number of
+conflicts is not reported, so @option{-W} and @option{--warning} then have
+no effect on the conflict report.
+
+@item deprecated
+Deprecated constructs whose support will be removed in future versions of
+Bison.
+
+@item empty-rule
+Empty rules without @code{%empty}. @xref{Empty Rules}. Disabled by
+default, but enabled by uses of @code{%empty}, unless
+@option{-Wno-empty-rule} was specified.
+
+@item precedence
+Useless precedence and associativity directives. Disabled by default.
+
+Consider for instance the following grammar:
+
+@example
+@group
+%nonassoc "="
+%left "+"
+%left "*"
+%precedence "("
+@end group
+%%
+@group
+stmt:
+ exp
+| "var" "=" exp
+;
+@end group
+
+@group
+exp:
+ exp "+" exp
+| exp "*" "num"
+| "(" exp ")"
+| "num"
+;
+@end group
+@end example
+
+Bison reports:
+
+@c cannot leave the location and the [-Wprecedence] for lack of
+@c width in PDF.
+@example
+@group
+warning: useless precedence and associativity for "="
+ %nonassoc "="
+ ^^^
+@end group
+@group
+warning: useless associativity for "*", use %precedence
+ %left "*"
+ ^^^
+@end group
+@group
+warning: useless precedence for "("
+ %precedence "("
+ ^^^
+@end group
+@end example
+
+One would get the exact same parser with the following directives instead:
+
+@example
+@group
+%left "+"
+%precedence "*"
+@end group
+@end example
+
+@item other
+All warnings not categorized above. These warnings are enabled by default.
+
+This category is provided merely for the sake of completeness. Future
+releases of Bison may move warnings from this category to new, more specific
+categories.
+
+@item all
+All the warnings except @code{yacc}.
+
+@item none
+Turn off all the warnings.
+
+@item error
+See @option{-Werror}, below.
+@end table
+
+A category can be turned off by prefixing its name with @samp{no-}. For
+instance, @option{-Wno-yacc} will hide the warnings about
+POSIX Yacc incompatibilities.
+
+@item -Werror
+Turn enabled warnings for every @var{category} into errors, unless they are
+explicitly disabled by @option{-Wno-error=@var{category}}.
+
+@item -Werror=@var{category}
+Enable warnings falling in @var{category}, and treat them as errors.
+
+@var{category} is the same as for @option{--warnings}, with the exception that
+it may not be prefixed with @samp{no-} (see above).
+
+Note that the precedence of the @samp{=} and @samp{,} operators is such that
+the following commands are @emph{not} equivalent, as the first will not treat
+S/R conflicts as errors.
+
+@example
+$ bison -Werror=yacc,conflicts-sr input.y
+$ bison -Werror=yacc,error=conflicts-sr input.y
+@end example
+
+@item -Wno-error
+Do not turn enabled warnings for every @var{category} into errors, unless
+they are explicitly enabled by @option{-Werror=@var{category}}.
+
+@item -Wno-error=@var{category}
+Deactivate the error treatment for this @var{category}. However, the warning
+itself won't be disabled, or enabled, by this option.
+
+@item -f [@var{feature}]
+@itemx --feature[=@var{feature}]
+Activate miscellaneous @var{feature}. @var{feature} can be one of:
+@table @code
+@item caret
+@itemx diagnostics-show-caret
+Show caret errors, in a manner similar to GCC's
+@option{-fdiagnostics-show-caret}, or Clang's @option{-fcaret-diagnotics}. The
+location provided with the message is used to quote the corresponding line of
+the source file, underlining the important part of it with carets (^). Here is
+an example, using the following file @file{in.y}:
+
+@example
+%type <ival> exp
+%%
+exp: exp '+' exp @{ $exp = $1 + $2; @};
+@end example
+
+When invoked with @option{-fcaret} (or nothing), Bison will report:
+
+@example
+@group
+in.y:3.20-23: error: ambiguous reference: '$exp'
+ exp: exp '+' exp @{ $exp = $1 + $2; @};
+ ^^^^
+@end group
+@group
+in.y:3.1-3: refers to: $exp at $$
+ exp: exp '+' exp @{ $exp = $1 + $2; @};
+ ^^^
+@end group
+@group
+in.y:3.6-8: refers to: $exp at $1
+ exp: exp '+' exp @{ $exp = $1 + $2; @};
+ ^^^
+@end group
+@group
+in.y:3.14-16: refers to: $exp at $3
+ exp: exp '+' exp @{ $exp = $1 + $2; @};
+ ^^^
+@end group
+@group
+in.y:3.32-33: error: $2 of 'exp' has no declared type
+ exp: exp '+' exp @{ $exp = $1 + $2; @};
+ ^^
+@end group
+@end example
+
+Whereas, when invoked with @option{-fno-caret}, Bison will only report:
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