On Thu, 2007-02-15 at 13:41 +0000, Robert Watson wrote: > Unfortunately, things are a bit more tricky. The problem is not so much the > API, where converting size_t/int is a relative non-event, rather, the ABI. > By > changing the size of a field in a data structure, you may change the layout > of > the structure, and hence the offset of other fields. This offset information > is compiled into binaries that access the structure -- hence being part of > the > ABI. On i386, the change from int to size_t doesn't modify the ABI, as both > int and size_t are 32-bit. However, on 64-bit platforms, int is 32-bit and > size_t is 64-bit: > > sledge:/tmp> uname -a > FreeBSD sledge.freebsd.org 7.0-CURRENT FreeBSD 7.0-CURRENT #898: Wed Feb 14 > 14:20:16 UTC 2007 [EMAIL PROTECTED]:/h/src/sys/amd64/compile/SLEDGE > amd64 > sledge:/tmp> ./size_t > sizeof int: 4 > sizeof size_t: 8 > > In practice, this means that all of the later fields in the data structure > will be offset by 4 bytes. This will affect any application that accesses > later fields in the structure but isn't recompiled. This is why DES and I > have been discussing this change as requiring kernel compatibility code, > which > would provide new system calls working with the new layout, and retain old > system calls working with the old layout. So we'd need to provide a new > shmctl() with the new structure, and an oshmctl() with the old layout. While > doing that, it makes sense to do all the other ABI-related things that we'd > like to get out of the way, such as fixing the types in shm_perm.
I understand ... i'll leave this up to you guys .. you have obviously a lot more hands on experience in these kinds of matters :) -- Pascal Hofstee _______________________________________________ freebsd-hackers@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-hackers To unsubscribe, send any mail to "[EMAIL PROTECTED]"
