C++ is very confusing at first, and I have found the errors are often
stubbornly unhelpful until you gain some experience with them.
I am not convinced that automatic casting is as risky as you think it is.
In my experience, C++ compilers do a very good job at balking if they
encounter any ambiguity whatsoever. That said, the error messages sometimes
don't help much. (See the previous paragraph.)
On Sun, Apr 26, 2015 at 6:15 AM, Jim Newton <[email protected]> wrote:
> Hi Jojo, I’m trying to figure out how to dump the warnings from xcode
> where I can post them to you. It will take me some
> time to figure this out.
>
>
> On the other hand, the other topic about casts making things confusing. I
> think there are probably lots of subtle implications of these automatic
> casts in C++ which programmers don’t realize. I know that some times cast
> automatically like you mentioned with certain numeric types. But I also
> understand that the programmer can overload casting operations between his
> own types. In addition the programmer can create template multiple
> argument functions which the compiler promises to use if the function gets
> called with particular combinations of types. It should be pretty easy to
> set up multiple ways to describe the casting. E.g., if there are
> overloaded casting operators transforming A->X, A->Y, X->B and Y->B, and
> there is a template defined on B and you call the template with A, I don’t
> know what will happen. Maybe this case is specified and everyone
> understands it. But certainly when you mix in multiple inheritance and
> functions of multiple arguments and lots of casting overloading, it will
> become difficult for the human being to figure out what is going to
> happen. And my suspicion is that not all compilers will handle some
> situations the same way.
>
> One thing that makes C++ powerful as it is used today, is that libraries
> set up so many intuitive operator overloadings and generic templates, that
> the naive beginner such as myself can easily write code which compiles and
> works or at least seems to work, but might be horribly inefficient or might
> fail under obscure conditions. I’ve noticed that somethings just work, and
> other things which should work (in my opinion) don’t.
>
> The case I found recently was that if I declare a variable as a set of
> objects of my class. I can call container.find(obj). but if I redefine to
> use deque rather than set, container.find(obj) fails, and on the mac it
> fails with a strange compiler error. I talked to a C++ expert about this
> and in his opinion it was obvious, but to me it just seemed inconsistent
> and strange.
>
>
> Jim
>
>
> > On 25 Apr 2015, at 14:20, Jojo-Schmitz [via MuseScore Developer] <
> [email protected]> wrote:
> >
> > Hi Jim
> >
> > What you call auto-casting, is really called default argument promotion.
> So
> > an function/method expecting a double would happily accept a float, a
> > function/method expecting a long would also take an int or short, and
> > without the need on any explicit cast. And this isn't even C++, but
> plain C.
> >
> > Casts in C++ come in different flavours, see e.g.
> >
> http://stackoverflow.com/questions/28002/regular-cast-vs-static-cast-vs-dyna
> <
> http://stackoverflow.com/questions/28002/regular-cast-vs-static-cast-vs-dyna
> >
> > mic-cast
> >
> > I'm continuously trying to make sure the code compiles without any
> warning
> > under Windows (as seen on my machine) as well as Linux (as seen on
> Travis),
> > and also occasionally did some work to fix some warnings in Mac (I
> usually
> > don't get to see those), but the vast majority of warnings in Mac are
> just
> > bogus, at least to my understanding.
> > Would be really nice to somehow get them fixed or silenced, as to not
> miss
> > tree the tree (of a valid warning) in the forest (of bogus ones)...
> >
> > Bye, Jojo
> >
> > -----Original Message-----
> > From: Jim Newton [mailto:[hidden email]
> <x-msg://14/user/SendEmail.jtp?type=node&node=7579210&i=0>]
> > Sent: Saturday, April 25, 2015 11:33 AM
> > To: [hidden email]
> <x-msg://14/user/SendEmail.jtp?type=node&node=7579210&i=1>
> > Subject: Re: [Mscore-developer] running tests on mac via xcode
> >
> > I also don't understand the C++ concept of casting. Of course I have a
> very
> > high level conceptual understanding. But the whole system seems to get
> > confusing at the extremes. I.e., if there are many different methods
> none
> > of which exactly match, and lots of ways to auto-cast the arguments.
> Which
> > one has priority, and do we know whether this decision happens the same
> way
> > on every version of every compiler on every architecture, independent of
> in
> > which order the files were compiled etc.
> >
> > I am very new to C++. I'm using xcode on the mac. When I compile
> > musescore, it compiles with no errors, but nevertheless with lots of
> > warnings. I'm afraid to fix any of the warnings because they are in
> code I
> > don't understand. It would be great if we (the collective developers)
> could
> > eliminate all the warnings. Not sure if that is even possible, as
> perhaps
> > some of the warnings are just plain wrong? Not sure.
> >
> >
> >
> >
> >
> >
> >
> > --
> > View this message in context:
> >
> http://dev-list.musescore.org/running-tests-on-mac-via-xcode-tp7579199p75792
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> http://dev-list.musescore.org/running-tests-on-mac-via-xcode-tp7579199p75792
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> > 09.html
> > Sent from the MuseScore Developer mailing list archive at Nabble.com.
> >
> >
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