Floating point exceptions with -pthread

Marc Olzheim marcolz at stack.nl
Wed May 4 14:58:50 PDT 2005

On Wed, May 04, 2005 at 05:25:04PM -0400, Daniel Eischen wrote:
> floorf() seems to fiddle with the FP control word.  The kernel
> and libpthread use fxsave and fxrstor respectively.  These
> save and restore the control word, but something may not be
> working correctly.

Hmm, as does ceilf. But trunf() the only other doing this, does not
get the sigFPE:

fstcw, then:

floorf()     ceilf()      truncf()
or  0x0400   or  0x0800   or 0x0c00
and 0xf7ff   and 0xfbff

and fldcw the modified version.

Then why is truncf() different... ? All abuse the 0x0c00 bits of the
control word.

-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 187 bytes
Desc: not available
Url : http://lists.freebsd.org/pipermail/freebsd-threads/attachments/20050504/ea33d7ba/attachment.bin

More information about the freebsd-threads mailing list