Re: Idle Thought - Compiling with C++

["martin.r.mathieson" <martin.r.mathieson () googlemail com>]

I am not sure about starting to make use of C++ features, but what I do find useful is maintaining a g++ build for a 
fairly large codebase I maintain. I have never even tried to run the resulting binary, but it catches certain errors 
that the C compiler does not. The most useful one is that C++ treats enums as proper types, so it catches assignments 
and comparisons that don't match the declared type. Also it is strict about pointer assignments, so you must add casts 
in many cases and I think this makes the code clearer.

Martin 




Sent from Samsung tabletDonald White <donald-white () cox net> wrote:On 2/9/2013 3:24 PM, Evan Huus wrote:
> On Sat, Feb 9, 2013 at 1:50 PM, Guy Harris <guy () alum mit edu> wrote:
> > (Subject line changed to match what you presumably intended.)
> Yes, thank you.
>
> > On Feb 9, 2013, at 6:41 AM, Evan Huus <eapache () gmail com> wrote:
> > > This just occurred to me as I was reading an article on GCC (which has
> > > recently migrated to using a C++ compiler, despite still being mostly
> > > written in C). I haven't given it a great deal of thought yet, but I
> > > figured I'd bring it up and see what general opinion was.
> > >
> > > At a first glance, building Wireshark with C++ compilers would give us
> > > two major benefits:
> >           ...
> >
> > > - Built-in exceptions. This would be additional migration work, but it
> > > would permit us to drop a non-trivial amount of code that we currently
> > > own in order to do our own exceptions.
> > >
> > > Note that I'm not suggesting we start writing Wireshark in C++ (that's
> > > an entirely different debate), but that we could compile using C++
> > > compilers, and then potentially sneak in a few C++ constructs where we
> > > used to roll our own.
> > Presumably by "start writing Wireshark in C++" you mean "rearchitecting Wireshark as a C++ program", as once you've 
> > snuck in one C++ construct you're writing in C++. :-)
> Fair point.
>
> > Note that some of Wireshark, i.e. the Qt GUI part, is already written in C++, and at least one third-party Wireshark 
> > plugin, i.e. the WSGD packet description language plugin:
> >
> >           http://wsgd.free.fr
> >
> > is written in C++.
> I was aware of the QT GUI, but not of the extension. As far as I'm
> aware, Gerald's been doing the vast majority of the QT work, so I
> didn't want to take that as indicative of a general interest.
>
> > See also
> >
> >           http://hub.opensolaris.org/bin/view/User+Group+rs-osug/evan-adams
> >
> > The Old Man and the C
> > Evan Adams
> > Sun Microsystems
> >
> > Abstract
> >
> > "You can't teach an old dog new tricks" goes the old proverb. This is a story about a pack of old dogs (C 
> > programmers) and their odyssey of trying to learn new tricks (C++ programming).
> >
> > C++ is a large, complex language which can easily be abused, but also includes many features to help programmers 
> > more quickly write higher quality code. The TeamWare group consciously decided which C++ features to use and, just 
> > as importantly, which features not to use. We also incrementally adopted those features we chose to use. This 
> > resulted in a successful C++ experience.
> Very interesting article - I agree with most of it. I personally have
> some C++ experience (though less than I do pure C), but I have no idea
> what kind of experience with it others have. I do think that slowly
> and carefully adopting certain limited features of it would make our
> lives easier, though honestly the primary reason I suggested it was
> because of how fed up I am with MSVC :)
>
> Evan
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I haven't done any Wireshark development recently, and all of the 
dissectors I have written were proprietary and not submitted.

That said, I have some experience with C to C++ transitions.  Twice in 
my career, the team I was with was given the job of maintaining legacy 
products written in C (several 100K lines of code) to maintain and 
enhance.  In both cases, our first step was to recompile with a C++ 
compiler.  This was done as a quick and intense effort without 
introducing any C++ language features.  We would just get the code to 
compile, link and pass its regression tests.  Only later did we replace 
#defines with consts, macros with inline functions and such.  I judged 
these efforts as being very beneficial in improving code quality.

As fixing and enhancing could not stop, a small special team was 
assigned the work.  They basically kept recompiling, transitioning and 
merging until they a had C++ equivalent code base.  Then, the whole team 
switched to the new code base.

Don
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