On 10/28/2016 09:29 PM, Colin Ian King wrote:
On 28/10/16 20:21, Manfred Spraul wrote:
Hi Colin,
On 10/28/2016 08:11 PM, Colin King wrote:
[...]
--- a/ipc/sem.c
+++ b/ipc/sem.c
@@ -1839,7 +1839,7 @@ SYSCALL_DEFINE4(semtimedop, int, semid, struct
sembuf __user *, tsops,
max = 0;
for (sop = sops; sop < sops + nsops; sop++) {
- unsigned long mask = 1 << ((sop->sem_num) % BITS_PER_LONG);
+ unsigned long mask = 1ULL << ((sop->sem_num) % BITS_PER_LONG);
Why 1ULL? Is 1UL not sufficient?
For example, 1UL i386 is 32 bits, where as 1ULL is 64.
Exactly: on i386, 'unsigned long" is 32 bits. BITS_PER_LONG is 32.
Thus with 1UL, the code should be correct.
With 1ULL & -Wconversion, gcc would even report a warning:
gcc -m32 -Wall -Wconversion -O1 test.c
test.c: In function ‘main’:
test.c:13:6: warning: conversion to ‘long unsigned int’ from ‘long
long unsigned int’ may alter its value [-Wconversion]
j= 1ULL << k;
^~~~
test.c:
#include <stdio.h>
#include <stdlib.h>
int main(int argc, char **argv)
{
unsigned long j;
int i;
for (i=1;i<argc;i++) {
long k;
k=atoi(argv[i]);
j= 1ULL << k;
printf("%d: %lu %ld.\n", i, j, k);
}
return 0;
}
--
Manfred
(still thinks "1UL" is what is required)
