On 23/08/2012 22:52, William Swanson wrote: > On Thu, Aug 23, 2012 at 12:49 PM, William Swanson <swanson...@gmail.com> > wrote: >>> Another option is a single inline assembly call for the "|=" if the above >>> code split does not help. >> >> I've had to do this in a few places, like when I need to atomically >> update a hardware flag. > > I just realized something horrible. Code like this is not safe: > > P1IFG &= ~P1_PWR_SW; > > There is no assurance that the "&=" operator will work atomically. > Even if it does compile to the correct "bis.b" instruction, what > happens if another IO pin toggles mid-instruction? Could the > transition be lost? Hopefully the chip designers accounted for this, > but it's still a scary thought. >
There is no guarantee that the compiler will produce a single "bis" instruction for such code (though it normally will) - as I said before, "volatile" gives you very few guarantees according to the standards. ------------------------------------------------------------------------------ Live Security Virtual Conference Exclusive live event will cover all the ways today's security and threat landscape has changed and how IT managers can respond. Discussions will include endpoint security, mobile security and the latest in malware threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ _______________________________________________ Mspgcc-users mailing list Mspgcc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/mspgcc-users
