SV *
overload_add_eq (a, b, third)
	SV *	a
	SV *	b
	SV *	third
CODE:
  RETVAL = overload_add_eq (aTHX_ a, b, third);
OUTPUT:  RETVAL

##</code><code>##

void
overload_add_eq (a, b, third)
	SV *	a
	SV *	b
	SV *	third
        CODE:
        overload_add_eq (aTHX_ a, b, third);
        XSRETURN_EMPTY; /* return empty stack */

##</code><code>##

SV * overload_add_eq(pTHX_ SV * a, SV * b, SV * third) {
    /* lengthy code  snipped */
}

##</code><code>##

void overload_add_eq(pTHX_ SV * a, SV * b, SV * third) {
     PERL_UNUSED_ARG(third); /* UPDATE: This line can be removed as irrelevant */
     mpz_add_ui(*(INT2PTR(mpz_t *, SvIVX(SvRV(a)))), *(INT2PTR(mpz_t *, SvIVX(SvRV(a)))), SvUV(b));
}

##</code><code>##

> perl -Mblib -MMath::GMPz -MDevel::Peek -wle "$x = Math::GMPz->new(1234); $x++;print $x; $x += 15; print $x; Dump($x);"
1235
Use of uninitialized value $x in print at -e line 1.

SV = PVIV(0x1abd93865e0) at 0x1abdad3ae48
  REFCNT = 1
  FLAGS = ()
  IV = 1837594613288
  PV = 0

##</code><code>##

> perl -Mblib -MMath::GMPz -MDevel::Peek -wle "$x = Math::GMPz->new(1234); $x++; print $x; Math::GMPz::overload_add_eq($x, 15, 0); print $x;"
1235
1250

##</code><code>##

> perl -Mblib -MMath::GMPz -MDevel::Peek -wle "$x = Math::GMPz->new(1234); $x++;print $x; $x += 15; print $x; Dump($x);"
1235
1250
SV = IV(0x2bfffa61b78) at 0x2bfffa61b88
  REFCNT = 1
  FLAGS = (ROK)
  RV = 0x2bfff38aac8
  SV = PVMG(0x2bfffa24a58) at 0x2bfff38aac8
    REFCNT = 1
    FLAGS = (OBJECT,IOK,READONLY,pIOK)
    IV = 3023652457216
    NV = 0
    PV = 0
    STASH = 0x2bfffa5e5e8       "Math::GMPz"