Hello Tom!

21 Jan 96 02:01, Tom Brown wrote to All:

 TB> I have been using C++ for some time now.  As a long-time C
 TB> programmer,
 TB> I don't use the object oriented features as much as I might.  It
 TB> seems as though a simple program with no templates, OpenClass
 TB> objects or containers comes out much larger than it ought to.

Ah... but it does come out that big, and you're lookin' for reasons, right? :-)

 TB> What I like most about the language is the way it lends itself to
 TB> grouping related functions.  My code looks like C code except I
 TB> do use cout and cerr all of the time.  I've often wondered why a
 TB> simple program with a main() and one object with four methods
 TB> (functions to me) needs to be 40K when the same thing in C comes
 TB> in at 14K.  I don't mean a similar thing in C.  If you take the
 TB> C++ object and simply break it down into the four functions and
 TB> compile the whole works as C code, it comes in a bunch smaller.
 TB> The size increase with C++ starts with larger .OBJs and more
 TB> run-time code is linked in, as well.

C++ has more runtime checking.  Objects also use more runtime checking than
non-objects, ESPECIALLY once you put a single 'virtual' function in!  It
has much checking of the pointers to figure out if this is a base object,
or a derived object, and how many derivations it has gone through and...
well... this happens at link time sometimes, and runtime other times.

 TB> I know that with C, I need to keep each function in it's own
 TB> source file so that the linker can link in only the functions
 TB> that it needs. I'm talking about object libraries specifically.
 TB> C++ seems to get out of hand if you put each method into it's own
 TB> source file.  I've got some pretty big objects (all in one source
 TB> file -> a .CPP and a .HPP),
 TB> so I'm guessing that if I instantiate one of these bad boys I get
 TB> the whole thing regardless of what methods are called in my
 TB> application.

I was under the opposite impression, since I know not all of the main C
libraries are compiled into my executables... :-/

 TB> Curiously, I find the performance of C++ to be very near C when I
 TB> don't use C++ specific features, even though the .EXEs are
 TB> larger.  I
 TB> don't care about hard disk space, but I would like to code as
 TB> efficiently as I can.

When speed becomes a problem, concentrate on that area.  If you find a
function eating way too  much time, first try getting it into another
thread.  If it is still killing your CPU, or you cannot change threads
(such as anything I write - I haven't figured out all the proper stuff yet
), hand-tune the routine via inline assemebly.  Otherwise, don't
worry about it... :-)  We all have 33 million cycles every second or more,
so another 100 isn't going to kill anyone.

BTW, this is more of a C++ question, and maybe should be taken to C_PLUSPLUS instead.

Darin McBride

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