Make clean solves problem ---> here's why...

[Manor Askenazi]

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* Actually, I did a `make clean' this morning and it seems to be working. *
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Hi David!

This proves that the trouble you were having is of the form alluded to 
by Ginger in her message:

  David,
      Since I'm not good about keeping my Makefile scrupulously correct,
  I often get whacked errors when I add to a class.  Deleting all binaries 
  and re-making is my first step.  Just a thought.

  Ciao, 
      Ginger

It's worth understanding exactly what this problem is about because
it is bound to trip you more than once ----> I remember one similar 
incident which almost cost the Institute a keyboard or a screen :-)

In any case, here's a slightly longer explanation of what Ginger is 
referring to:

Imagine that you have two classes A and B, where B inherits from A.
Assume also, that initially you compile your program and everything 
works great...

Now imagine that you edit the source for class A and recompile it.
Well, it is very likely that your makefile will not force the 
recompilation of class B (unless you were very careful to specify 
that B.o depends on A.h). 

This error tends to go unnoticed because, in general, editing class 
A will not affect class B unless you screw around with the size of 
A or the layout of A's instance variables (basically by declaring 
new variables or removing old variables or by changing the type of 
a variable).

Note that even if you *are* careful to ensure that in your makefile, 
B.o depends on (changes in) A.h (which is where its instance variables 
are declared), you could still get screwed -- this can happen if you 
have A is the superclass of B is the superclass of C. Now, even if you 
ensure that B will be re-compiled if A is re-compiled, C will not get
re-compiled because B.h was not changed! 

My guess is that to ensure a truly 100% correct compilation one would 
have to specify a dependency from C.o to B.o and from B.o to A.o... 

But I have never seen such a Makefile. 

Does anybody out there do this???

Who knows... :-)

Manor.

PS> A grown-up environment/compiler would automatically track all this 
    sort of shit for you...