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Mention that YYLLOC_DEFAULT is also invoked for syntax errors.

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Paul Eggert
2002-12-28 08:37:17 +00:00
parent d42f69cdf7
commit 96b93a3da4
1 changed files with 12 additions and 6 deletions
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@@ -3186,17 +3186,23 @@ Actually, actions are not the best place to compute locations. Since
locations are much more general than semantic values, there is room in locations are much more general than semantic values, there is room in
the output parser to redefine the default action to take for each the output parser to redefine the default action to take for each
rule. The @code{YYLLOC_DEFAULT} macro is invoked each time a rule is rule. The @code{YYLLOC_DEFAULT} macro is invoked each time a rule is
matched, before the associated action is run. matched, before the associated action is run. It is also invoked
while processing a syntax error, to compute the error's location.
Most of the time, this macro is general enough to suppress location Most of the time, this macro is general enough to suppress location
dedicated code from semantic actions. dedicated code from semantic actions.
The @code{YYLLOC_DEFAULT} macro takes three parameters. The first one is The @code{YYLLOC_DEFAULT} macro takes three parameters. The first one is
the location of the grouping (the result of the computation). The second one the location of the grouping (the result of the computation). When a
is an array holding locations of all right hand side elements of the rule rule is matched, the second parameter is an array holding locations of
being matched. The last one is the size of the right hand side rule. all right hand side elements of the rule being matched, and the third
parameter is the size of the rule's right hand side. When processing
a syntax error, the second parameter is an array holding locations of
the symbols that were discarded during error processing, and the third
parameter is the number of discarded symbols.
By default, it is defined this way for simple @acronym{LALR}(1) parsers: By default, @code{YYLLOC_DEFAULT} is defined this way for simple
@acronym{LALR}(1) parsers:
@example @example
@group @group
@@ -3491,7 +3497,7 @@ should use @code{$$} to designate the semantic value associated to the
(@pxref{Parser Function, , The Parser Function @code{yyparse}}). (@pxref{Parser Function, , The Parser Function @code{yyparse}}).
@strong{Warning:} as of Bison 1.875, this feature is still considered as @strong{Warning:} as of Bison 1.875, this feature is still considered as
experimental, as there was not enough users feedback. In particular, experimental, as there was not enough user feedback. In particular,
the syntax might still change. the syntax might still change.
@end deffn @end deffn