Re: Ada compared to C++

[dewar@cs.nyu.edu (Robert Dewar)]

Of course the key here is not out-of-date, but inconsistent, and indeed
Ed's arguments would be clearer with this modification.

Make is, as I have found out, having used it for GNAT for some time now,
totally inadequate. The fundamental problem is that the comparison of
greater than on time stamps just doesn't work. If you go back to a previous
version of the source with an old time stamp, then make thinks it's up to
date. Of course in the GNAT case, the binder complains, so you can't actually
build the inconsistent application that make thinks is just fine (but of
course you could in C or C++).

Now of course I realize that there are much more sophisticated tools than
make for ensuring consistency (e.g. clearcase from SGI, recently mentioned
in this newsgroup). If someone will promise me that all C++ applications
are built with such tools, and no one uses make or worse still, nothing at
all, then all would be well, but you know perfectly well this is not the
case (or perhaps I should say not the clearcase :-)

With Ada on the other hand, I know that everyone is using tools to ensure
consistency because you can't get around them (without doing something
very deliberate).

Note that there is nothing to stop the Ada approach from being grafted into
C++. An interesting project in the GCC world would be to make g++ share the
same consistency mechanisms that are used by GNAT. However, it is clear that
there is a real advantage in having these mechanisms clear at the language
level.

Going back to GNAT, we will continue to use make files indefinitely (unless
someone follows the GCC thoughts in the previous paragraph), since GNAT is
a mixed C/Ada application, and we need the make for the C part (and in any
case we use make for higher level control like building distributions and
running bootstraps).

However, the explicit list of dependencies in the GNAT makefile for the
compiler Ada sources is very irritating. For one thing, it is always one
step out of date, it is yesterdays dependencies, not todays. The solution
of course is a decent make program, and we are now working on one (its
actually quite simple to do) called gnatmake, and then the make file will
simply call gnatmake.