passing POD by value with const qualifiers. Silly or not?

Andre Wöbbeking Woebbeking at
Wed Feb 20 07:56:59 GMT 2008

On Wednesday 20 February 2008 08:42:26 Thiago Macieira wrote:
> Andre Wöbbeking wrote:
> >On Wednesday 20 February 2008 06:04:24 Matt Rogers wrote:
> >> Hi,
> >>
> >> So, I've been doing some review of decibel and I've seen some stuff
> >> like this (from kdereview/decibel/src/server/contactmanager.h)
> >>
> >> Decibel::ChannelInfo
> >> contactContactUsingAccount(const uint contact_id, const int
> >> account_handle, const int type, const bool suppress_handler);
> >>
> >>
> >> Most of us know that passing POD by value with a const qualifier is
> >> kinda silly, since it has next to zero real effect.
> I agree with Stephan and Andre here. I'll even give you examples from Qt:
> src/xmlpatterns/api - headers do not include const unnecessarily
> src/xmlpatterns/*~api - const is used on PODs
> [That's a zsh extendedglob]
> >It makes sense in the implementation but not in the API. As compromise
> > we could remove the const in the header files but leave them in the
> > source files (that is allowed for PODs).
> No, it's not. Not only that, some compilers mangle the "const" as well, so
> removing it if it was there is binary incompatible.

I'm not speaking about BIC or BC.

> This applies as well to return types:
> 	const int foo();
> That generates a warning in gcc 4.3, but you can't remove it because it's
> binary incompatible in MSVC.

AFAIK it's OK to have parameters without const in the declaration and with 
const in the implementation. Not sure about return values.

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