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doc: clean up the description of YYDEBUG

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* doc/bison.texi: Make it clearer that %define parse.trace is the
preferred options.
Fix a typo about api.prefix.
This commit is contained in:
Akim Demaille
2019-12-13 18:23:16 +01:00
parent b10366f296
commit d29e40a047
1 changed files with 25 additions and 25 deletions
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50
doc/bison.texi
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@@ -9971,10 +9971,30 @@ When a Bison grammar compiles properly but parses ``incorrectly'', the
@node Enabling Traces
@subsection Enabling Traces
There are several means to enable compilation of trace facilities:
There are several means to enable compilation of trace facilities, in
decresing order of preference:
@table @asis
@item the macro @code{YYDEBUG}
@item the variable @samp{parse.trace}
@findex %define parse.trace
Add the @samp{%define parse.trace} directive (@pxref{%define
Summary,,parse.trace}), or pass the @option{-Dparse.trace} option
(@pxref{Tuning the Parser}). This is a Bison extension. Unless POSIX and
Yacc portability matter to you, this is the preferred solution.
@item the option @option{-t} (POSIX Yacc compliant)
@itemx the option @option{--debug} (Bison extension)
Use the @samp{-t} option when you run Bison (@pxref{Invocation, ,Invoking
Bison}). With @samp{%define api.prefix @{c@}}, it defines @code{CDEBUG} to
1, otherwise it defines @code{YYDEBUG} to 1.
@item the directive @samp{%debug} (deprecated)
@findex %debug
Add the @code{%debug} directive (@pxref{Decl Summary, ,Bison Declaration
Summary}). This Bison extension is maintained for backward compatibility
with previous versions of Bison; use @code{%define parse.trace} instead.
@item the macro @code{YYDEBUG} (C/C++ only)
@findex YYDEBUG
Define the macro @code{YYDEBUG} to a nonzero value when you compile the
parser. This is compliant with POSIX Yacc. You could use
@@ -9984,36 +10004,16 @@ Prologue}).
If the @code{%define} variable @code{api.prefix} is used (@pxref{Multiple
Parsers, ,Multiple Parsers in the Same Program}), for instance @samp{%define
api.prefix x}, then if @code{CDEBUG} is defined, its value controls the
api.prefix @{c@}}, then if @code{CDEBUG} is defined, its value controls the
tracing feature (enabled if and only if nonzero); otherwise tracing is
enabled if and only if @code{YYDEBUG} is nonzero.
@item the option @option{-t} (POSIX Yacc compliant)
@itemx the option @option{--debug} (Bison extension)
Use the @samp{-t} option when you run Bison (@pxref{Invocation, ,Invoking
Bison}). With @samp{%define api.prefix @{c@}}, it defines @code{CDEBUG} to 1,
otherwise it defines @code{YYDEBUG} to 1.
@item the directive @samp{%debug}
@findex %debug
Add the @code{%debug} directive (@pxref{Decl Summary, ,Bison Declaration
Summary}). This Bison extension is maintained for backward
compatibility with previous versions of Bison.
@item the variable @samp{parse.trace}
@findex %define parse.trace
Add the @samp{%define parse.trace} directive (@pxref{%define
Summary,,parse.trace}), or pass the @option{-Dparse.trace} option
(@pxref{Tuning the Parser}). This is a Bison extension, which is especially
useful for languages that don't use a preprocessor. Unless POSIX and Yacc
portability matter to you, this is the preferred solution.
@end table
We suggest that you always enable the trace option so that debugging is
always possible.
@findex YYFPRINTF
The trace facility outputs messages with macro calls of the form
In C the trace facility outputs messages with macro calls of the form
@code{YYFPRINTF (stderr, @var{format}, @var{args})} where @var{format} and
@var{args} are the usual @code{printf} format and variadic arguments. If
you define @code{YYDEBUG} to a nonzero value but do not define
@@ -14168,7 +14168,7 @@ it. Using @samp{%define parse.error verbose} is preferred
@end deffn
@deffn {Macro} YYFPRINTF
Macro used to output run-time traces.
Macro used to output run-time traces in C.
@xref{Enabling Traces}.
@end deffn