[PPL-devel] Re: Feature request: optionally compile with support for exceptions

[Niels Möller]

Roberto Bagnara <bagnara at cs.unipr.it> writes:

> Not only I expect all allocations that may fail to be done through the
> custom allocation functions;  I also expect GMP not to leave inconsistent
> objects around in case of allocation failures.  And it would also be
> very desirable that no memory is leaked in that cases (this is harder
> to achieve and can be left as a desideratum).

I'm also a little confused. There are at least two ways to do it:
Either have the allocation functions return NULL, and then the GMP
functions allocating memory must check for that and set gmp_error to
GMP_ALLOCATE. But from my reading of the source (e.g. mpz/init.c),
there are no such checks. (In fact, it seems gmp_errno is only ever
set by the randomness functions. And I wouldn't miss it if it was
purged from the code; using global variables for error reporting is
ugly).

The other alternative is to expect the allocation function to longjmp
out on failure (and C++ exceptions is about the same thing, from GMP:s
point of view). Then GMP has to be careful not to leak any memory when
such jumps happen.

/Niels