On Wed, Dec 21, 2011 at 12:25:18PM -0500, John Baldwin wrote: > On Wednesday, December 21, 2011 11:13:10 am Kostik Belousov wrote: > > On Wed, Dec 21, 2011 at 10:31:11AM -0500, John Baldwin wrote: > > > On Tuesday, December 20, 2011 5:18:58 pm m...@freebsd.org wrote: > > > > On Tue, Dec 20, 2011 at 1:49 PM, John Baldwin <j...@freebsd.org> wrote: > > > > > Hmm, if these functions are expected to operate like 'write(2)' and > > > > > are > > > > > supposed to return the number of bytes written, shouldn't their > > > > > return value > > > > > be 'ssize_t' instead of 'int'? It looks like the system calls > > > > > themselves > > > > > already do the right thing in setting td_retval[] (they assign a > > > > > ssize_t to it > > > > > and td_retval[0] can hold a ssize_t on all of our current platforms). > > > > > It > > > > > would seem that the only change would be to the header and probably > > > > > syscalls.master. I guess this would require a symver bump to fix > > > > > though. > > > > > > > > An extended attribute larger than 2GB is a programming abuse, though. > > > > Technically int may not be 32 bits but it is on all supported > > > > platforms now. > > > > > > Today it is an abuse. In the 90's a 64-bit off_t was considered an abuse > > > by > > > some. :) > > > > > > The type should match the documented behavior. On OS X the set operation > > > doesn't return a size but instead returns a simple success/failure (0 or > > > -1) > > > for which an int is appropriate. However, the FreeBSD API documents that > > > it > > > operates like write and consumes the buffer. Note that the size of the > > > buffer passed to the 'set' and 'get' operations is a size_t, not an int, > > > and > > > the 'get' operations already return a ssize_t, not an int. > > > > Note that read(2)/write(2) do return int. I still have WIP patch to fix > > this, but after some conversations with Bruce I am not sure it is worth > > finishing. > > The manpages and /usr/include/unistd.h claim they return ssize_t. Is this > related to the changes to make uio_resid a size_t (I thought that went into > the tree)? If the problem is that the values read/write return may fall into > the range of only an int even on 64-bit platforms, that is different from the > return type which is part of the ABI. Yes, it is related. The type change for uio was done in advance.
Take a look at the first statement of sys_read() and sys_write():
if (uap->nbyte > INT_MAX)
return (EINVAL);
and at the copyinio(), which is used by scatter/gather versions of i/o
syscalls to copy in uiovec:
if (iov->iov_len > INT_MAX - uio->uio_resid) {
free(uio, M_IOV);
return (EINVAL);
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