From: Eran Gabber eran@research.att.com
Subject: a compiler bug?
Date: Tue, 26 Mar 1996 16:34:01 -0500 [thread overview]
Message-ID: <19960326213401.lfBe5RuahTCxWs28GPAL_7nBagx3JKWy9FQpexy8yO4@z> (raw)
Hi,
I found that assigning structure displays into an array of structures
with a post-increment index yields strange results.
The value of the index is wrong and the array has "holes".
The following C program demonstrates this behavior:
#include <u.h>
#include <libc.h>
enum {
N = 10,
};
typedef struct {
int p;
int q;
} T;
static int na, nb;
static T a[N], b[N];
void
main(int argc, char *argv[])
{
int i;
T x;
for (i = 0; i < N; i++) {
x = (T){10+i, 20+i};
a[na++] = x;
b[nb++] = (T){10+i, 20+i};
}
print("na=%d nb=%d\n", na, nb);
for (i = 0; i < N; i++)
print("a[%d]: %d %d\n", i, a[i].p, a[i].q);
for (i = 0; i < N; i++)
print("b[%d]: %d %d\n", i, b[i].p, b[i].q);
}
The contents of a and b should be equal, as well as na and nb.
The output is:
term% 8.out
na=10 nb=20
a[0]: 10 20
a[1]: 11 21
a[2]: 12 22
a[3]: 13 23
a[4]: 14 24
a[5]: 15 25
a[6]: 16 26
a[7]: 17 27
a[8]: 18 28
a[9]: 19 29
b[0]: 10 0
b[1]: 0 20
b[2]: 11 0
b[3]: 0 21
b[4]: 12 0
b[5]: 0 22
b[6]: 13 0
b[7]: 0 23
b[8]: 14 0
b[9]: 0 24
Regards,
Eran
Eran Gabber E-mail: eran@bell-labs.com
Bell Labs, Room MH 2C-234A http://cm.bell-labs.com/is/eran
600 Mountain Avenue Phone: 1-908-582-4354
Murray Hill, NJ 07974 Fax: 1-908-582-5809
next reply other threads:[~1996-03-26 21:34 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
1996-03-26 21:34 Eran [this message]
1996-03-27 6:27 forsyth
1996-03-27 6:56 forsyth
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