Re: [PORTS] Patch for m68k architecture (fwd)

>
> Hi Bruce!
>
> > I have already asked for you to try a change to template/linux_m68k
> > by changing the optimization -O2 to -O and see if you still need the
> > postgres.h fmgr_ptr change you did. I assume you are using egcs, right?
>
> Can't remember that you asked me... But anyway, it wouldn't help. It's
> defined in the SysV/m68k ABI that %d0 is used for scalar return values
> and %a0 for pointer values. Both gcc and egcs do it like this, and
> it's also independent from optimization level. (And, BTW, I didn't use
> egcs.)
>
> This behaviour is one of the most prominent porting problems to m68k.
> ANSI C says results are undefined if you call a function via pointer
> and the pointer is declared to return another type than the function
> actually returns. So m68k compilers conform to the standard here.
> However, most programmers never expect such problems... also because
> on most architectures it works without probs, because all values are
> returned in the same register.

Yes, we admit that we break the standard with fmgr_ptr, because we
return a variety of values depending on what function they call. It
appears the egcs optimization on the powerpc or alpha cause a problem
when optimization is -O2, but not -O. We may see more platforms with
problems as optimizers get smarter.

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Bruce Momjian | http://www.op.net/~candle
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