🚀 go-pugleaf

In article <1992Oct1.033932.22482@cs.aukuni.ac.nz> epoo1@cs.aukuni.ac.nz (Edouard Poor) writes:

>
>void startDecode( void )
>    {
>    /* Initialize the bit input routines.  Since this is dual-use code
>       we can only read in 8 bits of a possible 16 */
>
>    value = ( ( ( ( WORD ) fgetByte() ) << 8 ) | fgetByte() );
>
> ....
>
>One genuine bug.
>

Indeed so, but in the program not in the compiler.  The order of evaluation
of subexpressions is unspecified (except where there's a sequence point as with
operators such as &&).  This, by the way, is explicitly stated in K&R 1, not
an invention of ANSI.  It so happens that the Acorn compiler in this case
chooses to evaluate the right-hand call of fgetByte before the left-hand
one, for reasons which have nothing to do with the optimiser.  You have been
given one of the two values you ambiguously asked for, and can't very well
complain.

With regard to dhrystone figures, you seem to live in a different world from
the rest of us.  The ground rules for dhrystone are:
 *  - Separate compilation
 *  - No procedure merging
 *  - Otherwise, compiler optimizations are allowed but should be indicated
 *  - Default results are those without register declarations
No 'use default options' there, and indeed looking at the set of reported
dhrystone times, I don't see any which don't use at least -O; many use exotic
-O sub-options

Harry Meekings

I speak for myself alone, etc etc.