I have gcc-4.1 configured with ../gcc-4.1.0/configure --prefix=/usr
--libexecdir=/usr/lib --enable-shared --enable-threads=posix
--enable-__cxa_atexit --enable-c99 --enable-long-long --enable-clocale=gnu
--enable-languages=c,c++ --disable-multilib --disable-libstdcxx-pch
The following test generates the checksum of a dummy sun disk label.
cat > test.c << "EOF"
#include <stddef.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
typedef unsigned short __be16;
typedef unsigned int __be32;
struct sun_disklabel {
unsigned char info[128]; /* Informative text string */
unsigned char spare0[14];
struct sun_info {
unsigned char spare1;
unsigned char id;
unsigned char spare2;
unsigned char flags;
} infos[8];
unsigned char spare[246]; /* Boot information etc. */
__be16 rspeed; /* Disk rotational speed */
__be16 pcylcount; /* Physical cylinder count */
__be16 sparecyl; /* extra sects per cylinder */
unsigned char spare2[4]; /* More magic... */
__be16 ilfact; /* Interleave factor */
__be16 ncyl; /* Data cylinder count */
__be16 nacyl; /* Alt. cylinder count */
__be16 ntrks; /* Tracks per cylinder */
__be16 nsect; /* Sectors per track */
unsigned char spare3[4]; /* Even more magic... */
struct sun_partition {
__be32 start_cylinder;
__be32 num_sectors;
} partitions[8];
__be16 magic; /* Magic number */
__be16 csum; /* Label xor'd checksum */
};
int main(void)
{
struct sun_disklabel label;
__be16 csum, *ush;
memset(&label, 0xff, sizeof(label));
ush = ((__be16 *) (&label + 1)) - 1;
for (csum = 0; ush >= ((__be16 *) &label); )
csum ^= *ush--;
printf("Test checksum is %x\n", csum);
exit(0);
}
EOF
When this test is compiled with 'gcc test.c' or 'gcc -Os test.c' the checksum
is 0. The checksum is supposed to be 0. When the test is compiled with 'gcc -O2
test.c' the checksum is 0xffff. The same goes for -O1 and -O3. Compiling with
-Wall doesn't ouput any warnings. The last known version to work is gcc-4.0.2.
As far as I know the problem is in this loop:
for (csum = 0; ush >= ((__be16 *) &label); )
The problem also exists if the loop is changed to this:
while (ush >= ((__be16 *) &label))
--
Summary: Sun disklabel checksum code isn't being generated
properly.
Product: gcc
Version: 4.1.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: jciccone at gmail dot com
GCC build triplet: sparc64-unknown-linux-gnu
GCC host triplet: sparc64-unknown-linux-gnu
GCC target triplet: sparc64-unknown-linux-gnu
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27176
