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skeletons: make yysyntax_error_arguments a private detail

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We could just "inline yysyntax_error_arguments back" in the routines
it was originally extracted from, but I think the code is nicer to
read this way.

* data/skeletons/glr.c (yysyntax_error_arguments): Generate only for
detailed and verbose error messages.
* data/skeletons/yacc.c: Likewise.
* data/skeletons/lalr1.cc (parser::context::yysyntax_error_arguments):
Move as...
(parser::yysyntax_error_arguments_): this.
And only for detailed and verbose error messages.
This commit is contained in:
Akim Demaille
2020-03-26 08:15:35 +01:00
parent 1edc98f793
commit ee56b6e0f2
3 changed files with 140 additions and 144 deletions
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109
data/skeletons/yacc.c
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@@ -1197,63 +1197,9 @@ yyexpected_tokens (const yyparse_context_t *yyctx,
{
return yypstate_expected_tokens (yyctx->yyps, yyarg, yyargn);
}]])[
static int
yysyntax_error_arguments (const yyparse_context_t *yyctx,
int yyarg[], int yyargn) YY_ATTRIBUTE_UNUSED;
static int
yysyntax_error_arguments (const yyparse_context_t *yyctx,
int yyarg[], int yyargn)
{
/* Actual size of YYARG. */
int yycount = 0;
/* There are many possibilities here to consider:
- If this state is a consistent state with a default action, then
the only way this function was invoked is if the default action
is an error action. In that case, don't check for expected
tokens because there are none.
- The only way there can be no lookahead present (in yychar) is if
this state is a consistent state with a default action. Thus,
detecting the absence of a lookahead is sufficient to determine
that there is no unexpected or expected token to report. In that
case, just report a simple "syntax error".
- Don't assume there isn't a lookahead just because this state is a
consistent state with a default action. There might have been a
previous inconsistent state, consistent state with a non-default
action, or user semantic action that manipulated yychar.]b4_lac_if([[
In the first two cases, it might appear that the current syntax
error should have been detected in the previous state when yy_lac
was invoked. However, at that time, there might have been a
different syntax error that discarded a different initial context
during error recovery, leaving behind the current lookahead.]], [[
- Of course, the expected token list depends on states to have
correct lookahead information, and it depends on the parser not
to perform extra reductions after fetching a lookahead from the
scanner and before detecting a syntax error. Thus, state merging
(from LALR or IELR) and default reductions corrupt the expected
token list. However, the list is correct for canonical LR with
one exception: it will still contain any token that will not be
accepted due to an error action in a later state.]])[
*/
if (yyctx->yytoken != YYEMPTY)
{
int yyn;]b4_lac_if([[
YYDPRINTF ((stderr, "Constructing syntax error message\n"));]])[
yyarg[yycount++] = yyctx->yytoken;
yyn = yyexpected_tokens (yyctx, yyarg ? yyarg + 1 : yyarg, yyargn - 1);
if (yyn == -2)
return -2;]b4_lac_if([[
else if (yyn == 0)
YYDPRINTF ((stderr, "No expected tokens.\n"));]])[
else
yycount += yyn;
}
return yycount;
}
]])[
]b4_parse_error_case(
]b4_parse_error_bmatch(
[custom],
[[/* The token type of the lookahead of this context. */
static int
@@ -1278,8 +1224,7 @@ yyparse_context_location (const yyparse_context_t *yyctx)
/* User defined function to report a syntax error. */
static int
yyreport_syntax_error (const yyparse_context_t *yyctx]b4_user_formals[);]],
[simple],
[[]],
[detailed\|verbose],
[[#ifndef yystrlen
# if defined __GLIBC__ && defined _STRING_H
# define yystrlen(S) (YY_CAST (YYPTRDIFF_T, strlen (S)))
@@ -1369,6 +1314,56 @@ yytnamerr (char *yyres, const char *yystr)
#endif
]])[
static int
yysyntax_error_arguments (const yyparse_context_t *yyctx,
int yyarg[], int yyargn)
{
/* Actual size of YYARG. */
int yycount = 0;
/* There are many possibilities here to consider:
- If this state is a consistent state with a default action, then
the only way this function was invoked is if the default action
is an error action. In that case, don't check for expected
tokens because there are none.
- The only way there can be no lookahead present (in yychar) is if
this state is a consistent state with a default action. Thus,
detecting the absence of a lookahead is sufficient to determine
that there is no unexpected or expected token to report. In that
case, just report a simple "syntax error".
- Don't assume there isn't a lookahead just because this state is a
consistent state with a default action. There might have been a
previous inconsistent state, consistent state with a non-default
action, or user semantic action that manipulated yychar.]b4_lac_if([[
In the first two cases, it might appear that the current syntax
error should have been detected in the previous state when yy_lac
was invoked. However, at that time, there might have been a
different syntax error that discarded a different initial context
during error recovery, leaving behind the current lookahead.]], [[
- Of course, the expected token list depends on states to have
correct lookahead information, and it depends on the parser not
to perform extra reductions after fetching a lookahead from the
scanner and before detecting a syntax error. Thus, state merging
(from LALR or IELR) and default reductions corrupt the expected
token list. However, the list is correct for canonical LR with
one exception: it will still contain any token that will not be
accepted due to an error action in a later state.]])[
*/
if (yyctx->yytoken != YYEMPTY)
{
int yyn;]b4_lac_if([[
YYDPRINTF ((stderr, "Constructing syntax error message\n"));]])[
yyarg[yycount++] = yyctx->yytoken;
yyn = yyexpected_tokens (yyctx, yyarg ? yyarg + 1 : yyarg, yyargn - 1);
if (yyn == -2)
return -2;]b4_lac_if([[
else if (yyn == 0)
YYDPRINTF ((stderr, "No expected tokens.\n"));]])[
else
yycount += yyn;
}
return yycount;
}
/* Copy into *YYMSG, which is of size *YYMSG_ALLOC, an error message
about the unexpected token YYTOKEN for the state stack whose top is
YYSSP.]b4_lac_if([[ In order to see if a particular token T is a