On Sat, 17 Mar 2007, Max Laier wrote:
On Saturday 17 March 2007 20:09, Jeff Roberson wrote:
Any language lawyers care to comment on this?
I find this strange. According to the spec "(Decrementing is equivalent
to subtracting 1.)", but "pri = --pri % RQ_NQS;" will behave like you
expect, while "pri = (pri - 1) % RQ_NQS;" clearly didn't.
I noticed this as well.
When you do --pri, pri is promoted to int for the math and then demoted
back to char wich truncates the value. Subsequently this value is used
in the % operation, which gives the expected results.
When you do pri - 1 the intermediate result is promoted to a signed int
which doesn't yield the result you'd like when you mod with 64.
Jeff
On Sat, 17 Mar 2007, Jeff Roberson wrote:
jeff 2007-03-17 18:13:33 UTC
FreeBSD src repository
Modified files:
sys/kern sched_ule.c
Log:
- Cast the intermediate value in priority computtion back down to
unsigned char. Weirdly, casting the 1 constant to u_char still
produces a signed integer result that is then used in the %
computation. This avoids that mess all together and causes a 0 pri
to turn into 255 % 64 as we expect.
Reported by: kkenn (about 4 times, thanks)
Revision Changes Path
1.190 +1 -1 src/sys/kern/sched_ule.c
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