Re: [Sdcc-user] Erroneous compiler warning

[Mary-Ann J. <Mar...@di...>]

Yes, I want the compiler to optimise it away, but I'd like it to do so
without complaining about the "timeout" variable.  The following code
has similar problems:

void func(void)
{
  return;

  {
    int timeout;
    timeout =3D 0xFFFF;
    while (timeout--);
  }
}

Mary-Ann


Ken Jackson wrote:
> I don't know the answer, though I offer an observation.
>=20
> Most compilers will optimize away the delay that you are
> trying to implement.  Therefore you should declare timeout this way:
>=20
>   volatile int timeout;
>=20
> Also, when I do it that way, I don't get the warning.
>=20
> -Ken Jackson
>=20
> Mary-Ann Johnson writes:
> > If I compile the following code (SDCC 2.7.0):
> >
> > ------------------------------------------------ =20
> > void func(void)
> > {
> >   int timeout;
> >
> >   return;
> >
> >   timeout =3D 0xFFFF;
> >   while (timeout--);
> > }
> > ------------------------------------------------
> >
> > SDCC produces the following warnings:
> > "src/test.c:8: warning 84: 'auto' variable 'timeout' may
> > be used before initialization =20
> > src/test.c:8: warning 84: 'auto' variable 'timeout' may be
> > be used before initialization =20
> > src/test.c:8: warning 84: 'auto' variable 'timeout' may be
> > used before initialization"
> >
> > Any idea why?
> >
> > And before someone says "Don't call 'return' there!" -
> > this scenario happens when a macro is set to "return" to
> > eliminate the 2nd half of a function.
> >
> > Thanks,
> > Mary-Ann