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c++: clean a few issues wrt special tokens

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The C++ implementation of LAC did not skip the $undefined token,
probably because it was not exposed.  Expose it, and use clearer
names.

* data/skeletons/c++.m4: Don't define undef_token_ in yytranslate_,
but...
* data/skeletons/lalr1.cc (yy_undef_token_): here.
Use a more precise type to define yy_undef_token_ and yy_error_token_.
Unfortunately we move from a compile-time value defined via an enum to
a static const member.  Eventually we should make it constexpr.
Make LAC implementation more alike yacc.c's one.
This commit is contained in:
Akim Demaille
2019-12-01 08:03:29 +01:00
parent 9b4f0970fe
commit 94f70bd861
2 changed files with 10 additions and 7 deletions
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3
data/skeletons/c++.m4
View File

@@ -543,14 +543,13 @@ m4_define([b4_yytranslate_define],
]b4_translate[
};
const int user_token_number_max_ = ]b4_user_token_number_max[;
const token_number_type undef_token_ = ]b4_undef_token_number[;
if (t <= 0)
return yyeof_;
else if (static_cast<int> (t) <= user_token_number_max_)
return translate_table[t];
else
return undef_token_;]])[
return yy_undef_token_;]])[
}
]])

14
data/skeletons/lalr1.cc
View File

@@ -397,6 +397,10 @@ m4_define([b4_shared_declarations],
/// Pop \a n symbols from the stack.
void yypop_ (int n = 1);
/// Some specific tokens.
static const token_number_type yy_error_token_ = 1;
static const token_number_type yy_undef_token_ = ]b4_undef_token_number[;
/// Constants.
enum
{
@@ -404,7 +408,6 @@ m4_define([b4_shared_declarations],
yylast_ = ]b4_last[, ///< Last index in yytable_.
yynnts_ = ]b4_nterms_number[, ///< Number of nonterminal symbols.
yyfinal_ = ]b4_final_state_number[, ///< Termination state number.
yyterror_ = 1,
yyntokens_ = ]b4_tokens_number[ ///< Number of tokens.
};
@@ -1054,8 +1057,8 @@ b4_dollar_popdef])[]dnl
yyn = yypact_[yystack_[0].state];
if (!yy_pact_value_is_default_ (yyn))
{
yyn += yyterror_;
if (0 <= yyn && yyn <= yylast_ && yycheck_[yyn] == yyterror_)
yyn += yy_error_token_;
if (0 <= yyn && yyn <= yylast_ && yycheck_[yyn] == yy_error_token_)
{
yyn = yytable_[yyn];
if (0 < yyn)
@@ -1343,7 +1346,8 @@ b4_error_verbose_if([state_type yystate, const symbol_type& yyla],
if (!yy_pact_value_is_default_ (yyn))
{]b4_lac_if([[
for (int yyx = 0; yyx < yyntokens_; ++yyx)
if (yyx != yyterror_ && yy_lac_check_(yyx))
if (yyx != yy_error_token_ && yyx != yy_undef_token_
&& yy_lac_check_ (yyx))
{]], [[
/* Start YYX at -YYN if negative to avoid negative indexes in
YYCHECK. In other words, skip the first -YYN actions for
@@ -1353,7 +1357,7 @@ b4_error_verbose_if([state_type yystate, const symbol_type& yyla],
int yychecklim = yylast_ - yyn + 1;
int yyxend = yychecklim < yyntokens_ ? yychecklim : yyntokens_;
for (int yyx = yyxbegin; yyx < yyxend; ++yyx)
if (yycheck_[yyx + yyn] == yyx && yyx != yyterror_
if (yycheck_[yyx + yyn] == yyx && yyx != yy_error_token_
&& !yy_table_value_is_error_ (yytable_[yyx + yyn]))
{]])[
if (yycount == YYERROR_VERBOSE_ARGS_MAXIMUM)