Re: [boost] New Book: Introduction to the C++ Boost Libraries, Volume I - Foundations

Subject: Re: [boost] New Book: Introduction to the C++ Boost Libraries, Volume I - Foundations
From: Artyom (artyomtnk_at_[hidden])
Date: 2010-09-22 08:13:56

> > Part: 18.13 Volatile Variables
> 
> > >  In order  to rectify this situation we declare variables to be volatile
> > >   in order to disable register optimisations:
> > >
> > >   //  Shared variable
> > >   volatile int i2;
> > >   // The  same functions as above but use a volatile variable.
> > >   // Not  optimised anymore so results are always correct.
> > >   void FV1()  { while (true) i2++; }
> > >   void FV2() { while (true)  cout<<i2<<endl; }
> >
> > This is so wrong!
> 
> Please  explain why this is wrong. Is the code wrong? Is the example wrong? 
>Please note  that this is a snippet from the full test program where two 
>different threads  are started to execute FV1() and FV2().
> 

In addition to what was told, read following.

Read this: http://en.wikipedia.org/wiki/Volatile_variable#In_C_and_C.2B.2B
And this:  http://kernel.org/doc/Documentation/volatile-considered-harmful.txt

Artyom