Re: Compiled C vs C++
Hello,
Ulrich Hobelmann wrote:
If you want to program against binary code you need an ABI
(application binary interface), defining what can be expected from
binary code. If some implementation detail requires two variants of a
constructor to be available, which in general are different, then
both variants will be produced so they are available at link time.
Probably they will be produced consistently for all classes, because
it is an ABI.
Ok, that'd be a valid reason.
Then it is valid, because it is the reason.
Then try the general case, find an example, where the other variant
is called. AFAIK gcc needs the second to implement inheritance, and
other C++ compilers are similar. After 20+ years there should be
agreement on the best way to implement something that basic.
But having a class BAR that inherits from class FOO is nothing
different from having a struct BAR including a struct FOO and
implementing the same functions, delegating to FOO's function as
needed.
That's what you think, but an object at an address and a subobject of an
object at an address are two different things. I think, there are many
ways to get all issues done, calculating offsets, handling exceptions,
and whatever, and one way requires two variants of every constructor by
default, which might be equal, but are not in the general case. To get
a stable ABI both versions are produced by default, although it might
seem stupid to do so in the special case.
I don't need a second constructor. super() should simply call the
*usual* FOO constructor, I think.
You will have to try to solve the whole package of problems implementing
a C++ compiler to understand. Try to find a not so minimal example
spread across some translation units, where both variants of the
constructors are used, and try to understand why, or what would be more
difficult to achieve if another way had been chosen. I think the
example will have to include virtual functions to show anything
interesting, possibly even virtual inheritance. I do not know all the
details myself, but that's what I would try.
C++ has to offer quite some advantages, and it does so in a
architectured way, somehow using design patterns known before the times
of C++. If you read about design patterns, you will find the statement,
that architecture is about wasting at the right place. You are
objecting about a small wasted piece of a doghouse. The same idea
leading to a comparable piece in a skyscraper might save lots of
effort. I think you should find yourself a small house showing at least
a little bit of saving by that idea, instead of insisting on the
suboptimal doghouse. This group has seen lots of tries of proving C++
bad by doghouse examples. This is why you got so many responses you
don't like.
I think it is possible to fill several chapters introducing different
C++ implementations and comparing them. Basically this is what you are
asking for. Perhaps there is a book telling the story. (Design and
evolution of C++?). You simply cannot expect the whole deep story in a
newsgroup posting.
Bernd Strieder