Difference in malloc's behavior in 6.0

[Mayuresh <mayuresh%acm.org@localhost>]

lang/gprolog had an issue, due to which it was not working on NetBSD 6.0.

I know gprolog worked on NetBSD 4.0.

Have not tried / can't confirm about 5.x.

It worked on Linux.


Daniel Diaz, creator and maintainer of gprolog, fixed the issue and he
informed the following about the issue:

"NetBSD's malloc seems to have changed. In gprolog we use tagged pointers.
So we have to use 3 bits of the pointers. On 32 bits machine, we use
4-bytes alignement so we can use the 2 least significant bits (b1 and b0).
The last bit used is the most significant one (b31). Classically, malloc
(sbrk) does not return data with this bit set to 1 but some implementation
does (it occurs often when malloc relies on mmap to allocate memory). So I
fixed this using the dl_malloc (Doug Lea malloc)."



Can somebody throw some light on this change in behavior of malloc,
whether it was intentional and its purpose etc.

Mayuresh.