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c++: provide a means to clear symbols

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The symbol destructor is currently the only means to clear a symbol.
Unfortunately during error recovery we might have to clear the
lookahead, which is a local variable (yyla) that has not yet reached
its end of scope.

Rather that duplicating the code to destroy a symbol, or rather than
destroying and recreating yyla, let's provide a means to clear a
symbol.

Reported by Antonio Silva Correia, with an analysis from Michel d'Hooge.
<http://savannah.gnu.org/support/?108481>

* data/c++.m4, data/lalr1.cc (basis_symbol::clear, by_state::clear)
(by_type::clear): New.
(basic_symbol::~basic_symbol): Use clear.
This commit is contained in:
Akim Demaille
2015-01-08 10:19:10 +01:00
parent 5422471cbb
commit ee2f433512
3 changed files with 36 additions and 2 deletions
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24
data/c++.m4
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@@ -215,6 +215,9 @@ m4_define([b4_public_types_declare],
/// Destroy the symbol.
~basic_symbol ();
/// Destroy contents, and record that is empty.
void clear ();
/// Whether empty.
bool empty () const;
@@ -247,6 +250,9 @@ m4_define([b4_public_types_declare],
/// Constructor from (external) token numbers.
by_type (kind_type t);
/// Record that this symbol is empty.
void clear ();
/// Steal the symbol type from \a that.
void move (by_type& that);
@@ -329,6 +335,14 @@ m4_define([b4_public_types_define],
template <typename Base>
inline
]b4_parser_class_name[::basic_symbol<Base>::~basic_symbol ()
{
clear ();
}
template <typename Base>
inline
void
]b4_parser_class_name[::basic_symbol<Base>::clear ()
{]b4_variant_if([[
// User destructor.
symbol_number_type yytype = this->type_get ();
@@ -341,6 +355,7 @@ m4_define([b4_public_types_define],
// Type destructor.
]b4_symbol_variant([[yytype]], [[value]], [[template destroy]])])[
Base::clear ();
}
template <typename Base>
@@ -379,12 +394,19 @@ m4_define([b4_public_types_define],
: type (yytranslate_ (t))
{}
inline
void
]b4_parser_class_name[::by_type::clear ()
{
type = empty_symbol;
}
inline
void
]b4_parser_class_name[::by_type::move (by_type& that)
{
type = that.type;
that.type = empty_symbol;
that.clear ();
}
inline