lumiwa at gmail.com
Thu Jan 9 13:50:26 UTC 2014
On Wednesday 08 January 2014 19:19:18 Frank Leonhardt wrote:
> On 08/01/2014 18:37, Ajtim wrote:
> > Hi!
> > My system:
> > FreeBSD 10.0-RC4 #0 r260130: Tue Dec 31 17:10:01 UTC 2013 root at snap.freebsd.org:/usr/obj/usr/src/sys/GENERIC amd64
> > I had bellow warnings in mail from version FreeBSD 10.0-ALPHA and it is still on. Do I need to make some settings or..., please?
> > Thank you.
> > +WARNING pid 1752 (python2.7): ioctl sign-extension ioctl ffffffff80087467
> > +WARNING pid 1762 (python2.7): ioctl sign-extension ioctl ffffffff80087467
> I hate snakes!
> As to this, in case no one comes by that knows the answer, this wouldn't
> worry me greatly. ioctl takes values that are unsigned long; generally
> considered to be 32-bit unsigned values except when it's not. gcc
> defaults to 64-bit on AMD64. I have a horrible feeling that CLANG
> doesn't, and that FreeBSD 10 uses CLANG instead of gcc. I haven't been
> brave enough to try it. OpenCL specifies that long will be 64-bit
> regardless of platform, but that doesn't make it true.
> This is obviously bleating about a 64-bit value which looks like a -ve
> 32-bit number (high bit set). Compilers moving a signed integer value
> into a type with more bits WILL sign-extend, which means the high bit is
> propagated through the "new" high-order bits. HOWEVER, when the device
> driver is checking for commands it's not going to worry about the
> high-order bits - if its expecting a 32-bit scalar but the architecture
> gives it 64-bit instead it's not going to matter. It'll either check bit
> 31 (which remains unchanged) or, worst case, test for -ve (in which case
> you want the sign extend). It shouldn't do this, of course, because it's
> not a signed number and therefore can only be +ve. Hence the bleat.
> Methinks there's probably a line in python that's calling ioctl with an
> int instead of a ulong, and I bet CLANG comes in to it somewhere.
> Regards, Frank.
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Thank you very much for explanation. Looks like that is not bad but it is not nice everyday read "WARNINGS".
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