Numerical maximum in XS

[Tassilo von Parseval]

Hi,

right now I'm lost a bit in the muddle of the various perl compilation
flags and the sizes of some C datatypes. The task is simply to get the
numerical maximum of a list of values. Could someone have a look at the
following XSUB, especially at the #defines at the beginning? In
particular, I am not sure about using long doubles when 64bit integers
are in effect:

    SV*
    max (...)
        PROTOTYPE: @
        CODE:
        {
    #if defined USE_LONG_DOUBLE || defined USE_MORE_BITS  || \
        defined USE_LONG_LONG   || defined USE_64_BIT_INT || \
        defined USE_64_BIT_ALL
    #   define MINDOUBLE LDBL_MIN
            register long double max;
    #else
    #   define MINDOUBLE DBL_MIN
            register double max;
    #endif
            register int i;
            
            if (items == 1) {
                RETVAL = &PL_sv_undef;
                goto done;
            }
            
            if (SvOK(ST(0))) {
                RETVAL = ST(1);
                max = SvNV(ST(1));
            } else {
                RETVAL = &PL_sv_undef;
                max = MINDOUBLE;
            }
            for (i = 2; i < items ; i++) {
                if (!SvOK(ST(i)))
                    continue;
                if (SvNV(ST(i)) > max) {
                    max = SvNV(ST(i));
                    RETVAL = ST(i);
                }
            }
            SvREFCNT_inc(RETVAL);
        done:
            ;
        }
        OUTPUT:
            RETVAL

Cheers,
Tassilo
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