sigaction inconsistancy (here I go again)

[John W. DeBoskey]

Hi,

   Running -current...

   I'm trying to verify SIGFPE handling and am finding some
interesting issues. In the following test program, a divide
by zero is done and the SIGFPE delivered.

$ ./fp
sig == 8
code== 0
z has the value 1.000000


   It seems that from <machine/trap.h> the value of code should
have been:

/* codes for SIGFPE/ARITHTRAP */ 
#define     FPE_FLTDIV_TRAP     0x3     /* floating/decimal divide by zero */


   ie: 3 and not 0.

   Also, I haven't gone into the code yet, but the floating point
registers are not saved into the sigcontext so that they can be
inspected and modified as appropriate.

Thanks,
John

ps: I also noted that SA_RESTART is not documented in the man page
    with the other mask bits, but instead is mentioned in a follow-on
    statement. Just slightly misleading.


--------------------------------------------------------------------------
#include <stdio.h>
#include <floatingpoint.h>
#include <signal.h>


void fphand(int sig, int code, struct sigcontext *scp)
{
   fprintf(stderr,"sig == %d\n",sig);
   fprintf(stderr,"code== %d\n",code);
   return;
}

void
setup()
{
  int rc;
  struct sigaction act, oact;

  act.sa_handler = &fphand;
  act.sa_mask    = 0;
  act.sa_flags   = SA_RESTART; /* not doc'd in man page */

  rc = sigaction(SIGFPE, &act, &oact);
  if (rc) {
     perror("sigaction");
     exit(1);
  }
  return;
}

double
doit(double x, double y)
{
   return(x / y);
}

int
main()
{

   double x,y,z;
   fp_except_t mask = FP_X_DZ;

   setup();
   fpsetmask(mask);

   x = 1.0;
   y = 0.0;

   z = doit(x,y);

   printf("z has the value %f\n",z);
   return((int) z);
}



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