[GD-General] Assertions, pre/post-conditions and call tracing

[Brian H. <bri...@py...>]

I've gotten into the habit of making tons of function pre-conditions and 
post-conditions that can optionally be compiled away.  This is a Eiffel 
habit picked up second-hand from a former coworker of mine.

In Eiffel, you can set up a bunch of safeguards to do basic sanity 
checking.  The safeguards are pre-conditions (validate state and parameters 
before a method/"feature" is executed); post-conditions (validate state and 
parameters after a "feature" is executed); and class-invariants (check the 
integrity of the object after ANY "feature" is executed).

Eiffel does this with "require" and "ensure" clauses that are analogous to 
assert() expressions in C++, but are a bit more readable.  In addition, the 
"ensure" clause is guaranteed to be evaluated no matter how the function is 
exited (so you don't have to do a "goto ensure" all over your code to make 
sure you exit out the same place).

I don't believe there's any clean way to do a class-invariant in C++, but I 
may be wrong on that count.  The closest thing I can think of is making 
each class declare an InvarianceChecker class that is instanced at the 
beginning of each method and whose constructor/destructor pair do verification.

Related to this is the ability to halt the debugger when a verification 
fails (which I assume can be done portably by * ( int * ) 0 = 0 ), and 
bring up a dialog box with A/R/F a la Microsoft.  Finally, having a stack 
trace available so that I can see what function call list was causing the 
problem would be nice.

I can do a lot of this with assert(), but I'm hoping there's a better way 
to do all this.  I'm sure there might be some magic with exception handling 
that could be done but, as usual, I fear anything new in C++ that might not 
be portable.

Anyway, I'm interested to hear what other types of infrastructure people 
have devised for this type of stuff.

-Brian