integer overflow yields incorrect results and buffer overflow on 64-bit machines
tg at swox.com
Mon Feb 25 21:24:55 CET 2008
"Patrick Pelissier" <patrick.pelissier at gmail.com> writes:
> Unfortunately, changing the _mp_size and _mp_alloc fields to long
> cannot be done without breaking compatibility (the size of the type
> should not change).
> I am pondering some hairy solutions for GMP 5, stealing bits from the
> _mp_alloc field for use in the _mp_size field, and letting the
> remaining _mp_alloc bits be coded as a little home-brew floating point
Don't forget that gmp.h defines many macro functions which access
_mp_size field directly:
mpz_abs / mpz_fits_uint_p / mpz_get_ui / ...
The idea is to make old compiled-in versions of these work as long as
operands are < 2^37 bits. Greater operands will require recompile.
Do you think that could work?
You can't avoid breaking binary compatibility for GMP 5, I think.
Maybe, but I'll give it a serious thought.
If I fail, I might keep mpz as it is, with the limitations to about
2^37 bits. Then compile the same sources for huge operands, with some
alternative function prefix, such as "mpzzz_".
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