Re: [HACKERS] postgresql bug report (fwd)

> The Hermit Hacker <scrappy(at)hub(dot)org> writes:
> > it seems that this problem is a type casting/promotion bug in the
> > source. The
> > routine _bt_checkkeys() in backend/access/nbtree/nbtutils.c calls
> > int2eq() in
> > backend/utils/adt/int.c via a function pointer
> > *fmgr_faddr(&key[0].sk_func). As
> > the type information for int2eq is lost via the function pointer,
> > the compiler
> > passes 2 ints, but int2eq expects 2 (preformatted in a 32bit reg)
> > int16's.
> > This particular bug goes away, if I for example change int2eq to:
>
> > bool
> > int2eq(int32 arg1, int32 arg2)
> > {
> > return (int16)arg1 == (int16)arg2;
> > }
>
> Yow. I can't believe that we haven't seen this failure before on a
> variety of platforms. Calling an ANSI-style function that has char or
> short args is undefined behavior if you call it without benefit of a
> prototype, because the parameter layout is allowed to be different.
> Apparently, fewer compilers exploit that freedom than I would've thought.
>
> Really, *all* of the builtin-function routines ought to take arguments
> of type Datum and then do the appropriate Get() macro to extract what
> they want from 'em. That's a depressingly large amount of work, but
> at the very least the functions that take bool and int16 have to be
> changed...

I concur in your Yow. Lots of changes, and I am surprised we have not
been bitten by this before. Added to TODO:

Fix function pointer calls to take Datum args for char and int2 args

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