It pushes a value on the return stack

Yeaaah ... it pushes a value onto the stack ... but does that mean it returns a value ? (It's also pushing onto the stack something that's already on the stack, isn't it ? .... which doesn't do much to help the intellectually impaired :-) I thought there would have to be an XSRETURN() before anything was returned ... or a RETVAL ....

We see (in INLINE.h): 
#define Inline_Stack_Push(x)    XPUSHs(x)

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Also: 
#define Inline_Stack_Return(x)    XSRETURN(x)

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In Inline::C, we have to Inline_Stack_Return(x) if we wish to return anything from a 'void' function. Since Inline::C and XS are essentially one and the same thing, I expected that we would have to explicitly XSRETURN(x) from an XSub (if we wanted to return anything).

Let's concentrate (for the moment, anyway) on how to rewrite my 'overload_add_eq' in such a way that the refcount increase is not needed. I tried: 
void overload_add_eq(SV * obj, SV * addon, SV * third) {
     dXSARGS;
     Card* c = (Card *)SvIV(SvRV(obj));
     c->value += SvIV(addon);
     XPUSHs(obj);
}

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but still got the same failure with the '+=" operator. (Again, when explicitly calling overload_add_eq($obj, $addon, 0); there's no problem.)

Shit!! ... but hang on ... I also tried: 
void overload_add_eq(SV * obj, SV * addon, SV * third) {
     dXSARGS;
     Card* c = (Card *)SvIV(SvRV(obj));
     c->value += SvIV(addon);
     XPUSHs(obj);
     XSRETURN(1);
}

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and that worked fine with the '+=' overloading ... and no increase to the refcount !!! It also worked fine when I explicitly called overload_add_eq($obj, $addon, 0);(This might even constitute "progress".)

So ... I guess one remaining question is "how come I have to call both dXSARGS and XSRETURN (whereas Robert Hyde's GMP code didn't have to do that) ?"

Another question is "Has anything been achieved by rewriting 'overload_add_eq' ?". I guess the answer to that question will be "no" ... the proof will be in the benchmarking.

Thanks for the feedback, Anno. Please don't take my questions/objections/refutations as anything other than the ramblings of one who is both ill-informed and a little dim :-)

Cheers,
Rob

In reply to Re^4: Overload '+=' with XSub by syphilis
in thread Overload '+=' with XSub by syphilis

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