http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55222
Bug #: 55222
Summary: weird unstable "array subscript is above array bounds"
warning
Classification: Unclassified
Product: gcc
Version: 4.8.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
AssignedTo: unassig...@gcc.gnu.org
ReportedBy: akim.demai...@gmail.com
The following piece of code is a reduced version of a parser generated by
Bison. It triggers a new warning (which must be very recently added to 4.8, as
last week or so there were no such warning AFAICT).
One issue is that the warning looks like a certainty, "array subscript is above
array bounds", well, no it is not, and another is that if I remove the previous
line, which displays "yyi", then the warning disappears. This is fishy (at
least to my eyes).
$ cat array.c
#include <stdio.h>
typedef unsigned char uint8;
typedef signed char int8;
/* YYR2[YYN] -- Number of symbols composing right hand side of rule YYN. */
static const uint8 yyr2[] =
{
0, 2, 0
};
/* YYPRHS[YYN] -- Index of the first RHS symbol of rule number YYN in
YYRHS. */
static const uint8 yyprhs[] =
{
0, 0, 3
};
/* YYRHS -- A `-1'-separated list of the rules' RHS. */
static const int8 yyrhs[] =
{
4, 0, -1, -1
};
void
yy_reduce_print (int yyrule)
{
int yyi;
for (yyi = 0; yyi < yyr2[yyrule]; yyi++)
{
fprintf (stderr, "$%d = ", yyi);
fprintf (stderr, "%d\n", yyrhs[yyprhs[yyrule] + yyi]);
}
}
$ gcc-mp-4.8 -Wall -O3 array.c -c
array.c: In function 'yy_reduce_print':
array.c:32:37: warning: array subscript is above array bounds [-Warray-bounds]
fprintf (stderr, "%d\n", yyrhs[yyprhs[yyrule] + yyi]);
^
$ gcc-mp-4.8 --version
gcc-mp-4.8 (MacPorts gcc48 4.8-20121028_0) 4.8.0 20121028 (experimental)
Copyright (C) 2012 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
$ gcc-mp-4.7 -Wall -O3 array.c -c
$ gcc-mp-4.7 --version
gcc-mp-4.7 (MacPorts gcc47 4.7.2_2) 4.7.2
Copyright (C) 2012 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
$
