C compiler bug

[Mark G. Johnson]

In article <9007131953.AA08463 at prism> ae504pw at prism.gatech.edu writes:
  >I believe I may have found a bug in the C compiler on the Iris.
  >I compiled the following program, taken from the April 1985
  >PC Tech Journal ...
  >
  > [code for "High Performance CRC Computation Routine" removed]
  >
  >Something is definitely amiss here!  On a whim I compiled and ran
  >the identical code on a Sequent S81.  The results in that case are
  >quite different as seen below.
  >

Lint found little to complain about, so I tried the experiment of
compiling and running the program on a Sun SPARCstation 1, an
Apollo DN4000, and a MIPS RC3240.  All three of these produced the same
output as the IRIS.  So the scorecard thus far is:


    Printed the result                  Printed the result that
   John Forrest wanted                  John Forrest didn't want
---------------------------------------------------------------------------
  Sequent  S81  DYNIX V3.0.17.9      SGI   Iris 4D/120GTX   Irix 3.2
                                     Sun   SPARCstation 1   SunOs 4.0.3c
                                     MIPS  RC3240           RISC/os 4.50
                                     Apollo DN4000          BSD 4.2 DOMAIN-IX

The "wrong answer" machines contain 4 different CPUs (R2000, Cy7C601,
R3000, 68020) and employ 3 different C compilers.

Here is the output from the SPARCstation 1.  "diff" says it is identical to
the DN4000 and the RC3240 output.

 00 - 0000  0000  0000  0000  0000  0000  0000  0000
 08 - 0000  0000  0000  0000  0000  0000  0000  0000
 10 - 0000  0000  0000  0000  0000  0000  0000  0000
 18 - 0000  0000  0000  0000  0000  0000  0000  0000
 20 - 0000  0000  0000  0000  0000  0000  0000  0000
 28 - 0000  0000  0000  0000  0000  0000  0000  0000
 30 - 0000  0000  0000  0000  0000  0000  0000  0000
 38 - 0000  0000  0000  0000  0000  0000  0000  0000
 40 - 0000  0000  0000  0000  0000  0000  0000  0000
 48 - 0000  0000  0000  0000  0000  0000  0000  0000
 50 - 0000  0000  0000  0000  0000  0000  0000  0000
 58 - 0000  0000  0000  0000  0000  0000  0000  0000
 60 - 0000  0000  0000  0000  0000  0000  0000  0000
 68 - 0000  0000  0000  0000  0000  0000  0000  0000
 70 - 0000  0000  0000  0000  0000  0000  0000  0000
 78 - 0000  0000  0000  0000  0000  0000  0000  0000
 80 - 0000  0000  0000  0000  0000  0000  0000  0000
 88 - 0000  0000  0000  0000  0000  0000  0000  0000
 90 - 0000  0000  0000  0000  0000  0000  0000  0000
 98 - 0000  0000  0000  0000  0000  0000  0000  0000
 a0 - 0000  0000  0000  0000  0000  0000  0000  0000
 a8 - 0000  0000  0000  0000  0000  0000  0000  0000
 b0 - 0000  0000  0000  0000  0000  0000  0000  0000
 b8 - 0000  0000  0000  0000  0000  0000  0000  0000
 c0 - 0000  0000  0000  0000  0000  0000  0000  0000
 c8 - 0000  0000  0000  0000  0000  0000  0000  0000
 d0 - 0000  0000  0000  0000  0000  0000  0000  0000
 d8 - 0000  0000  0000  0000  0000  0000  0000  0000
 e0 - 0000  0000  0000  0000  0000  0000  0000  0000
 e8 - 0000  0000  0000  0000  0000  0000  0000  0000
 f0 - 0000  0000  0000  0000  0000  0000  0000  0000
 f8 - 0000  0000  0000  0000  0000  0000  0000  0000


TestArray1 CRC = 0x0000


TestArray2 CRC = 0x0000


Text = [This is a test message.]
CRC = 0000
-- 
 -- Mark Johnson	
 	MIPS Computer Systems, 930 E. Arques M/S 2-02, Sunnyvale, CA 94086
	(408) 524-8308    mark at mips.com  {or ...!decwrl!mips!mark}