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yacc.c: extract yyerror_message_arguments
Isolate a function that returns the list of expected and unexpected tokens. It will be exposed to users willing to customize their error messages. * data/skeletons/yacc.c (yyparse_context_t): New. (yyerror_message_arguments): New, extracted from yysyntax_error.
This commit is contained in:
Akim Demaille
@@ -1046,6 +1046,95 @@ yy_lac (yy_state_t *yyesa, yy_state_t **yyes,
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}
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}]])[
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]m4_if(b4_percent_define_get([[parse.error]]), [simple], [],
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[[typedef struct
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{
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yy_state_t *yyssp;
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int yytoken;]b4_lac_if([[
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yy_state_t *yyesa;
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yy_state_t **yyes_p;
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YYPTRDIFF_T *yyes_capacity_p;]])[
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} yyparse_context_t;
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static int
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yysyntax_error_arguments (const yyparse_context_t *yyctx,
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const char *yyarg[], int yyargn)
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{
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/* Actual size of YYARG. */
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int yycount = 0;
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/* There are many possibilities here to consider:
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- If this state is a consistent state with a default action, then
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the only way this function was invoked is if the default action
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is an error action. In that case, don't check for expected
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tokens because there are none.
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- The only way there can be no lookahead present (in yychar) is if
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this state is a consistent state with a default action. Thus,
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detecting the absence of a lookahead is sufficient to determine
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that there is no unexpected or expected token to report. In that
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case, just report a simple "syntax error".
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- Don't assume there isn't a lookahead just because this state is a
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consistent state with a default action. There might have been a
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previous inconsistent state, consistent state with a non-default
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action, or user semantic action that manipulated yychar.]b4_lac_if([[
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In the first two cases, it might appear that the current syntax
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error should have been detected in the previous state when yy_lac
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was invoked. However, at that time, there might have been a
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different syntax error that discarded a different initial context
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during error recovery, leaving behind the current lookahead.]], [[
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- Of course, the expected token list depends on states to have
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correct lookahead information, and it depends on the parser not
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to perform extra reductions after fetching a lookahead from the
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scanner and before detecting a syntax error. Thus, state merging
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(from LALR or IELR) and default reductions corrupt the expected
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token list. However, the list is correct for canonical LR with
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one exception: it will still contain any token that will not be
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accepted due to an error action in a later state.]])[
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*/
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if (yyctx->yytoken != YYEMPTY)
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{
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int yyn = yypact[+*yyctx->yyssp];]b4_lac_if([[
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YYDPRINTF ((stderr, "Constructing syntax error message\n"));]])[
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yyarg[yycount++] = yytname[yyctx->yytoken];
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if (!yypact_value_is_default (yyn))
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{]b4_lac_if([[
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int yyx;
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for (yyx = 0; yyx < YYNTOKENS; ++yyx)
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if (yyx != YYTERROR && yyx != YYUNDEFTOK)
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{
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{
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int yy_lac_status = yy_lac (yyctx->yyesa, yyctx->yyes_p, yyctx->yyes_capacity_p,
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yyctx->yyssp, yyx);
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if (yy_lac_status == 2)
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return -2;
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if (yy_lac_status == 1)
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continue;
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}]], [[
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/* Start YYX at -YYN if negative to avoid negative indexes in
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YYCHECK. In other words, skip the first -YYN actions for
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this state because they are default actions. */
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int yyxbegin = yyn < 0 ? -yyn : 0;
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/* Stay within bounds of both yycheck and yytname. */
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int yychecklim = YYLAST - yyn + 1;
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int yyxend = yychecklim < YYNTOKENS ? yychecklim : YYNTOKENS;
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int yyx;
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for (yyx = yyxbegin; yyx < yyxend; ++yyx)
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if (yycheck[yyx + yyn] == yyx && yyx != YYTERROR
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&& !yytable_value_is_error (yytable[yyx + yyn]))
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{]])[
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if (yycount == yyargn)
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{
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yycount = 1;
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break;
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}
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yyarg[yycount++] = yytname[yyx];
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}
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}]b4_lac_if([[
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else
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YYDPRINTF ((stderr, "No expected tokens.\n"));]])[
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}
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return yycount;
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}
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]])[
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]m4_case(b4_percent_define_get([[parse.error]]), [verbose],
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[[# ifndef yystrlen
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@@ -1135,6 +1224,7 @@ yytnamerr (char *yyres, const char *yystr)
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}
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# endif
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/* Copy into *YYMSG, which is of size *YYMSG_ALLOC, an error message
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about the unexpected token YYTOKEN for the state stack whose top is
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YYSSP.]b4_lac_if([[ In order to see if a particular token T is a
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@@ -1147,8 +1237,7 @@ yytnamerr (char *yyres, const char *yystr)
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yy_lac returned 2]])[. */
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static int
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yysyntax_error (YYPTRDIFF_T *yymsg_alloc, char **yymsg,
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]b4_lac_if([[yy_state_t *yyesa, yy_state_t **yyes,
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YYPTRDIFF_T *yyes_capacity, ]])[yy_state_t *yyssp, int yytoken)
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const yyparse_context_t *yyctx)
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{
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enum { YYERROR_VERBOSE_ARGS_MAXIMUM = 5 };
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/* Internationalized format string. */
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@@ -1161,76 +1250,15 @@ yysyntax_error (YYPTRDIFF_T *yymsg_alloc, char **yymsg,
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/* Cumulated lengths of YYARG. */
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YYPTRDIFF_T yysize = 0;
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/* There are many possibilities here to consider:
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- If this state is a consistent state with a default action, then
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the only way this function was invoked is if the default action
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is an error action. In that case, don't check for expected
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tokens because there are none.
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- The only way there can be no lookahead present (in yychar) is if
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this state is a consistent state with a default action. Thus,
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detecting the absence of a lookahead is sufficient to determine
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that there is no unexpected or expected token to report. In that
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case, just report a simple "syntax error".
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- Don't assume there isn't a lookahead just because this state is a
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consistent state with a default action. There might have been a
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previous inconsistent state, consistent state with a non-default
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action, or user semantic action that manipulated yychar.]b4_lac_if([[
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In the first two cases, it might appear that the current syntax
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error should have been detected in the previous state when yy_lac
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was invoked. However, at that time, there might have been a
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different syntax error that discarded a different initial context
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during error recovery, leaving behind the current lookahead.]], [[
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- Of course, the expected token list depends on states to have
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correct lookahead information, and it depends on the parser not
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to perform extra reductions after fetching a lookahead from the
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scanner and before detecting a syntax error. Thus, state merging
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(from LALR or IELR) and default reductions corrupt the expected
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token list. However, the list is correct for canonical LR with
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one exception: it will still contain any token that will not be
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accepted due to an error action in a later state.]])[
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*/
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if (yytoken != YYEMPTY)
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{
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int yyn = yypact[+*yyssp];]b4_lac_if([[
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YYDPRINTF ((stderr, "Constructing syntax error message\n"));]])[
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yyarg[yycount++] = yytname[yytoken];
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if (!yypact_value_is_default (yyn))
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{]b4_lac_if([[
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int yyx;
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for (yyx = 0; yyx < YYNTOKENS; ++yyx)
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if (yyx != YYTERROR && yyx != YYUNDEFTOK)
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{
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{
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int yy_lac_status = yy_lac (yyesa, yyes, yyes_capacity,
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yyssp, yyx);
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if (yy_lac_status == 2)
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return 2;
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if (yy_lac_status == 1)
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continue;
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}]], [[
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/* Start YYX at -YYN if negative to avoid negative indexes in
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YYCHECK. In other words, skip the first -YYN actions for
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this state because they are default actions. */
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int yyxbegin = yyn < 0 ? -yyn : 0;
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/* Stay within bounds of both yycheck and yytname. */
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int yychecklim = YYLAST - yyn + 1;
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int yyxend = yychecklim < YYNTOKENS ? yychecklim : YYNTOKENS;
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int yyx;
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for (yyx = yyxbegin; yyx < yyxend; ++yyx)
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if (yycheck[yyx + yyn] == yyx && yyx != YYTERROR
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&& !yytable_value_is_error (yytable[yyx + yyn]))
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{]])[
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if (yycount == YYERROR_VERBOSE_ARGS_MAXIMUM)
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{
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yycount = 1;
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break;
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}
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yyarg[yycount++] = yytname[yyx];
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}
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}]b4_lac_if([[
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else
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YYDPRINTF ((stderr, "No expected tokens.\n"));]])[
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}
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{
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int yyn
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= yysyntax_error_arguments (yyctx, yyarg,
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YYSIZEOF (yyarg) / YYSIZEOF (*yyarg));
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if (yyn == -2)
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return 2;
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else
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yycount = yyn;
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}
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switch (yycount)
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{
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@@ -1760,11 +1788,11 @@ yyerrlab:
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[simple],
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[[ yyerror (]b4_yyerror_args[YY_("syntax error"));]],
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[verbose],
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[[# define YYSYNTAX_ERROR yysyntax_error (&yymsg_alloc, &yymsg, \]b4_lac_if([[
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yyesa, &yyes, &yyes_capacity, \]])[
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yyssp, yytoken)
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[[# define YYSYNTAX_ERROR yysyntax_error (&yymsg_alloc, &yymsg, &yyctx)
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{
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char const *yymsgp = YY_("syntax error");
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yyparse_context_t yyctx
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= {yyssp, yytoken]b4_lac_if([[, yyesa, &yyes, &yyes_capacity]])[};
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int yysyntax_error_status;]b4_lac_if([[
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if (yychar != YYEMPTY)
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YY_LAC_ESTABLISH;]])[
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