Experimental Physics and
Industrial Control System

"Walters, M \(Malcolm\)" <[email protected]> · Wed, 10 May 2006 08:42:39 +0100

Although other implementations may not be throwing exceptions, it
doesn't mean they are working as you expect. Casting double precision
numbers greater than LONG_MAX cannot work since there is no long
representation of them.

Running the following code using gcc on Linux shows that all in this
case the result of casting DBL_MAX to a long is LONG_MIN.

To write code that will always work, the value to be cast should be
compared to LONG_MAX first. To be really defensive, a case for negative
numbers, or those below LONG_MIN should also be added.

Malcolm

/* Test to show behaviour of casting of limits*/

#include "float.h"
#include "limits.h"

double dMax=DBL_MAX;
long lMax;

int main(int argc, char * argv[]){

    lMax=(long)dMax;
    printf("%e %d %d\n",dMax,lMax,LONG_MIN);
}

> -----Original Message-----
> From: Matt Rippa [mailto:[email protected]] 
> Sent: 10 May 2006 02:49
> To: [email protected]
> Subject: MIPS epicsEventWaitWithTimeout(()
> 
> Hi all,
> 
> We're getting a floating point exception running iocInit() on 
> a mips hkbaja47 with 3.14.8.2 exampleApp. Specifically this 
> is the "timerQueue" task. Tracking this down it points to 
> epicsEventWaitWithTimeout() inside 
> base-3.14.8.2/src/libCom/osi/os/vxWorks/osdEvent.c
> 
> The double timeOut passed in is DBL_MAX size (1.79769e+308) 
> and used to calculate a semTake timeout. Basically, semTake 
> and wait a very long time:
> 
> int ticks = timeOut*sysClkRateGet();
> status = semTake((SEM_ID)id,ticks);
> 
> The mips can't seem to handle the double to int conversion 
> and ends up with an FPE and I think it's FPE_INVALID_OP.
> 
> It can handle this when ticks is clipped to LONG_MAX*1.0. 
> LONG_MAX*1.1 fails. We're wondering if there's any other 
> gotchas if we do this for our mips targets?
> 
> Of course it would be better if we could all run the same 
> code. :-) Maybe we need to disable some FPE's for the mips? 
> Does EPICS rely on disabling FPE's for all tasks? 
> 
> 
> Many thanks,
> -Matt
> 
> 
> iocInit()
> Starting iocInit
> ##############################################################
> ##############
> ###  EPICS IOC CORE built on May  8 2006
> ###  EPICS R3.14.8.2 $R3-14-8-2$ $2006/01/06 15:55:13$
> ##############################################################
> ##############
> 
> FPE Exception
> Exception Program Counter: 0x80d3c22c
> Status Register: 0x30006701
> Cause Register: 0x0000003c
> Task: 0x80f20870 "timerQueue"
> iocInit: All initialization complete
> 
> 
> -> tt 0x80ac70f0
> 80024434 vxTaskEntry    +c  : epicsThreadSleepQuantum 
> (&epicsThreadCallEntryPoint, 80acf48c, 0, 0)
> 808cea18 epicsThreadSleepQuantum+78 : 
> epicsThreadCallEntryPoint (eeeeeeee, eeeeeeee, eeeeeeee, eeeeeeee)
> 808c2f04 epicsThreadCallEntryPoint+a4 : 
> timerQueueActive::run(void) (eeeeeeee, eeeeeeee, eeeeeeee, eeeeeeee)
> 808d4ee4 timerQueueActive::run(void)+40 : 
> epicsEvent::wait(double) (800cfb5c, eeeeeeee, eeeeeeee, eeeeeeee)
> 808c8804 epicsEvent::wait(double)+28 : 
> epicsEventWaitWithTimeout (eeeeeeee, 80acf494, 808c7a48, 80acfe10)
> --------------------------------
> 
> -> ti 0x80f20870
> 
>   NAME        ENTRY       TID    PRI   STATUS      PC       
> SP     ERRNO  DELAY
> ---------- ------------ -------- --- ---------- -------- 
> -------- ------- -----
> timerQueue 80d3c028     80f20870 129 SUSPEND    80d3c22c 
> 80f205b8       0     0
> 
> stack: base 0x80f20870  end 0x80f1d990  size 11840  high 1464 
>   margin 10376
> 
> options: 0xc
> VX_DEALLOC_STACK    VX_FP_TASK
> 
> $0   =                0   at   = ffffffff80d60000   v0   =    
>            3c
> v1   = ffffffff80f20870   a0   = ffffffff80f28c90   a1   =    
>             0
> a2   =         7fefffff   a3   = ffffffffffffffff   t0   =    
>      30006701
> t1   =         30006700   t2   =                4   t3   =    
>             0
> t4   =                0   t5   =                0   t6   =    
>             0
> t7   =                0   s0   = ffffffff80f28c90   s1   = 
> ffffffff80f20870
> s2   = ffffffff80f28e6c   s3   = ffffffff80d34080   s4   =    
>             0
> s5   =                0   s6   =                0   s7   =    
>             0
> t8   =                0   t9   =                0   k0   = 
> 8007823ceeeeeeee
> k1   =                0   gp   = ffffffff80119dd8   sp   = 
> ffffffff80f205b8
> s8   =                0   ra   = ffffffff80d3c21c
> sr   = 30006701           pc   = 80d3c22c
> 
> 
> fpcsr  =  1000014
> fp0    =      Inf   fp2    =        2   fp4    = 6.31152e+08  
>  fp6    =        0
> fp8    =        0   fp10   =        0   fp12   =        0   
> fp14   =        0
> fp16   =        0   fp18   =        0   fp20   = 1.79769e+308 
>   fp22   =        0
> fp24   =        0   fp26   =        0   fp28   =        0   
> fp30   =        0
> 
> FPE Exception
> Exception Program Counter: 0xvalue = 80d3c22c0
> Status Register: 0x = 0x30006701
> Cause Register: 0x00000003c
> 
> 
> 

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System