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From: janowsky@math.rutgers.edu (Steven Janowsky)
Newsgroups: alt.sys.sun,ru.qa,comp.unix.wizards
Subject: optimazion bug in C compiler on SS1+?
Message-ID: <Mar.11.15.31.37.1991.24890@math.rutgers.edu>
Date: 11 Mar 91 20:31:40 GMT
References: <1991Mar11.185411.2414@ssd.kodak.com>
Followup-To: alt.sys.sun
Distribution: na
Organization: Rutgers Univ., New Brunswick, N.J.
Lines: 21

The following program (part of a random number generator) generates NaN
when compiled O2, O3, or O4 but works as expected if O1 or no optimiztion.
SS1+ running 4.0.3c

Any clues? (Please mail response to janowsky@hilbert.rutgers.edu)

#include <stdio.h>
main()
{
  int seed;
  double rand_a, rand_t;

  seed = 34;
  rand_a= -1.0 + 1.0 / 2147483648.0;
  rand_t=seed/2147483648.0;
  printf("%g\n",rand_t);
  rand_t *= 16807;
  rand_t += rand_a * ((int) rand_t);
  if(rand_t >= 1.0) rand_t += rand_a;
  printf("%g\n",rand_t);
}