Re: [paho-dev] Using C++ with the Paho C client library

[Ian Craggs <icraggs@xxxxxxxxxxxxxxxxxxxxxxx>]

Well, that is a different logic/purpose to Frank's (provide guidance on 
which parameters are not changed).  And to part of mine, which would be 
to help the writer and maintainer of the C API in preventing accidental 
alteration of const parameters.

I'd rather make all the changes at once, rather than have someone else 
question the lack of const on other parameters or structures at a later 
date.  But all updates have to allow non-const C code to work unchanged.

Ian

On 18/05/13 16:50, Roger Light wrote:
> Hi Ian,
>
> I was suggesting the pragmatic approach that would allow people using
> C++ to use the Paho C library with string literals without requiring a
> cast to (char *).
>
> Declaring all arguments as const where appropriate is a good goal, but
> it's not as much of a problem as the above.
>
> Cheers,
>
> Roger
>
> On Fri, May 17, 2013 at 12:01 PM, Ian Craggs
> <icraggs@xxxxxxxxxxxxxxxxxxxxxxx> wrote:
> > Hi Roger,
> >
> > I don't see why it should be unimportant that a member of a structure is not
> > const while the structure is const.  If the purpose is to help the writer of
> > a function using the data not to inadvertently modify caller data, then they
> > are both important.
> >
> > Maybe I misunderstand the purpose of the suggestion of adding const to these
> > fields.  What do we hope to achieve by doing so, if not the reason I stated
> > above?  And in that case what principle would we be following in deciding
> > which fields to apply const to, and which not?
> >
> > Ian
> >
> >
> > On 17/05/13 11:43, Roger Light wrote:
> > > Hi Ian,
> > >
> > > > what about the elements of the connectOptions, willOptions and SSLOptions
> > > > structures, for instance?
> > > Neither SSLOptions nor willOptions are directly exposed in the
> > > external API because they are only used as members of connectOptions.
> > > connectOptions itself can be const because none of its members are
> > > modified. My understanding is that it is not important that, for
> > > example, the username member of connectOptions is not const even
> > > though connectOptions may be. Username is mutable but connectOptions
> > > is not.
> > >
> > > Regards,
> > >
> > > Roger
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