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yacc: restructure and fix yysyntax_error

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I would like to offer new ways to build the error message.  As a first
step, let's simplify yysyntax_error whose first loop does two things
at the same time: (i) collect the tokens to be reported in the error
message, and (ii) accumulate their sizes and possibly return
"overflow".  Let's pull (ii) in a second step.

Then test 525 (regression.at:1193: parse.error=verbose overflow)
failed.  This test checks that we correctly report "memory overflow"
when the error message is too large.  However the test is mistaken: it
is triggered in a place where there are five (large) expected tokens,
so anyway we would not display them, so there is no (memory) overflow
here!  Transform this test to (i) check that indeed there is no
overflow, and (ii) create syntax_error3 which does check the intended
behavior, but with four expected tokens.

* data/skeletons/yacc.c (yysyntax_error): First compute the list of
arguments, then compute yysize.
* tests/regression.at (parse.error=verbose overflow): Enhance and fix.
This commit is contained in:
Akim Demaille
2019-12-31 07:28:59 +01:00
parent 78bb152a63
commit f983d00e77
2 changed files with 30 additions and 24 deletions
Download Patch File Download Diff File Expand all files Collapse all files

34
data/skeletons/yacc.c
View File

@@ -1184,15 +1184,12 @@ yysyntax_error (YYPTRDIFF_T *yymsg_alloc, char **yymsg,
*/
if (yytoken != YYEMPTY)
{
int yyn = yypact[+*yyssp];
YYPTRDIFF_T yysize0 = yytnamerr (YY_NULLPTR, yytname[yytoken]);
yysize = yysize0;]b4_lac_if([[
int yyn = yypact[+*yyssp];]b4_lac_if([[
YYDPRINTF ((stderr, "Constructing syntax error message\n"));]])[
yyarg[yycount++] = yytname[yytoken];
if (!yypact_value_is_default (yyn))
{]b4_lac_if([[
int yyx;
for (yyx = 0; yyx < YYNTOKENS; ++yyx)
if (yyx != YYTERROR && yyx != YYUNDEFTOK)
{
@@ -1212,7 +1209,6 @@ yysyntax_error (YYPTRDIFF_T *yymsg_alloc, char **yymsg,
int yychecklim = YYLAST - yyn + 1;
int yyxend = yychecklim < YYNTOKENS ? yychecklim : YYNTOKENS;
int yyx;
for (yyx = yyxbegin; yyx < yyxend; ++yyx)
if (yycheck[yyx + yyn] == yyx && yyx != YYTERROR
&& !yytable_value_is_error (yytable[yyx + yyn]))
@@ -1220,18 +1216,9 @@ yysyntax_error (YYPTRDIFF_T *yymsg_alloc, char **yymsg,
if (yycount == YYERROR_VERBOSE_ARGS_MAXIMUM)
{
yycount = 1;
yysize = yysize0;
break;
}
yyarg[yycount++] = yytname[yyx];
{
YYPTRDIFF_T yysize1
= yysize + yytnamerr (YY_NULLPTR, yytname[yyx]);
if (yysize <= yysize1 && yysize1 <= YYSTACK_ALLOC_MAXIMUM)
yysize = yysize1;
else
return 2;
}
}
}]b4_lac_if([[
# if ]b4_api_PREFIX[DEBUG
@@ -1256,14 +1243,19 @@ yysyntax_error (YYPTRDIFF_T *yymsg_alloc, char **yymsg,
# undef YYCASE_
}
/* Compute error message size. Don't count the "%s"s, but reserve
room for the terminator. */
yysize = (yystrlen (yyformat) - 2 * yycount) + 1;
{
/* Don't count the "%s"s in the final size, but reserve room for
the terminator. */
YYPTRDIFF_T yysize1 = yysize + (yystrlen (yyformat) - 2 * yycount) + 1;
if (yysize <= yysize1 && yysize1 <= YYSTACK_ALLOC_MAXIMUM)
yysize = yysize1;
else
return 2;
int yyi;
for (yyi = 0; yyi < yycount; ++yyi)
{
YYPTRDIFF_T yysize1 = yysize + yytnamerr (YY_NULLPTR, yyarg[yyi]);
if (yysize <= yysize1 && yysize1 <= YYSTACK_ALLOC_MAXIMUM)
yysize = yysize1;
else
return 2;
}
}
if (*yymsg_alloc < yysize)

20
tests/regression.at
View File

@@ -1219,7 +1219,7 @@ AT_DATA_GRAMMAR([input.y],
%%
start: syntax_error1 check syntax_error2 ;
start: syntax_error1 check syntax_error2 check syntax_error3;
// Induce a syntax error message whose total length causes yymsg in
// yyparse to be reallocated to size YYSTACK_ALLOC_MAXIMUM, which
@@ -1251,13 +1251,26 @@ check:
}
;
// Now overflow.
// We used to overflow memory here because the first four "expected"
// tokens plus rest of the error message is greater that 255 bytes.
// However there are *five* expected tokens here, so anyway we will
// *not* display these tokens. So the message fits, no overflow.
syntax_error2:
"123456789112345678921234567893123456789412345678951234567896123A"
| "123456789112345678921234567893123456789412345678951234567896123B"
| "123456789112345678921234567893123456789412345678951234567896123C"
| "123456789112345678921234567893123456789412345678951234567896123D"
| "123456789112345678921234567893123456789412345678951234567896123E"
| error 'd' 'e' 'f'
;
// Now overflow.
syntax_error3:
"123456789112345678921234567893123456789412345678951234567896123A"
| "123456789112345678921234567893123456789412345678951234567896123B"
| "123456789112345678921234567893123456789412345678951234567896123C"
| "123456789112345678921234567893123456789412345678951234567896123D"
;
%%
@@ -1265,7 +1278,7 @@ syntax_error2:
]AT_YYERROR_DEFINE[
/* Induce two syntax error messages (which requires full error
recovery by shifting 3 tokens). */
]AT_YYLEX_DEFINE(["abc"])[
]AT_YYLEX_DEFINE(["abcdef"])[
int
main (void)
{
@@ -1288,6 +1301,7 @@ AT_COMPILE([[input]])
AT_PARSER_CHECK([[input]], [[2]], [],
[[syntax error, unexpected 'a', expecting 123456789112345678921234567893123456789412345678951234567896123A or 123456789112345678921234567893123456789412345678951234567896123B or 123456789112345678921234567893123456789412345678951234567896123C
syntax error, unexpected 'd'
syntax error
memory exhausted
]])