How much should I cleanup?

[Andrew Cagney]

> When is it important to make sure that I have cleanups in place?  My
> understanding is that it's important if I have control of a block of
> memory that I want to xfree() after doing some work, but where that
> xfree() might not be reached because of exceptional circumstances.

Just assume the exception is the norm - you're going to need to do a 
clean-up.  The internals doco suggests several conventions.

> So, if that's correct: what are 'exceptional circumstances'?  I assume
> error() and related functions count.  I don't know exactly what QUIT
> does; do I have to be careful if there are QUIT's in between the
> xmalloc() and the xfree()?  (Are those the only places where GDB pays
> attention to ^C's?)  Any other situations?

Failed memory read, no frame.

> Sigh.  C has its benefits, but ease of memory management isn't one of
> them.  Every time I have to write a cleanup function, every time I
> have to think about whether to alloca() memory for a string or to
> xmalloc() it (and every time I can't alloca() it because I'm returning
> the string in question), I get another grey hair.  (Though the grey
> hair falls out soon thereafter, for better or for worse.)

Ah, yes.  C++ `is the answer' :-^

> David Carlton
> carlton@math.stanford.edu

Andrew