[Boost-users] [thread] variables in thread examples require 'volatile'?

Subject: [Boost-users] [thread] variables in thread examples require 'volatile'?
From: Gabriel Redner (gredner_at_[hidden])
Date: 2009-12-07 18:59:28

Dear Boosters,

I'm involved in a bit of a dispute in which a colleague is claiming
that 'volatile' is necessary to make certain synchronization patterns
correct.  As part of my response I pointed out that the boost.thread
examples don't use it, but he maintains his position - saying that the
examples are flawed.  I'm frankly somewhat out of my element here, and
I'd like to get input from people who have presumably thought about
this stuff a good deal.

The example in question is here, under "synopsis":
http://www.boost.org/doc/libs/1_41_0/doc/html/thread/synchronization.html#thread.synchronization.condvar_ref

The claim is that 'volatile' is needed on the boolean, otherwise the
compiler might cache the boolean in a register, and the loop would
never exit.  He cites for support two articles:

http://www.ddj.com/cpp/184403766
https://www.securecoding.cert.org/confluence/display/seccode/DCL17-C.+Beware+of+miscompiled+volatile-qualified+variables

Who's right?

Thanks,
-Gabe