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Re: how to use volatile key word?

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Am 26.06.2012 18:10, schrieb 伏虎:
> how to use volatile key word?
> 
> Assume I have a global variable shared by two or more tasks.  Do I
> need to declare it as volatile?
> 
> When will a non-volatile global variable be written back to memory
> from a register copy? Before a function call? Or before the return
> statement?

Using it in such a context is not sufficient. Even with volatile there
would be no guarantee that the compiler would load a consistent value
from memory. E.g in extreme cases it could load the upper half of a
variable in one load and and the lower half with another. Your program
then could see a mix of two different values.

The feature that you would be needing is C11's _Atomic and not
volatile. Many compilers already provide similar features as
extensions. P99 supports part of the C11 syntax on top of gcc and
cousins.

Jens

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how to use volatile key word? 伏虎 <fuhu314@hotmail.com> - 2012-06-26 09:10 -0700
  Re: how to use volatile key word? Xavier Roche <xroche@free.fr.NOSPAM.invalid> - 2012-06-26 18:56 +0200
  Re: how to use volatile key word? Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-06-26 12:57 -0400
  Re: how to use volatile key word? Jens Gustedt <jens.gustedt@loria.fr> - 2012-06-26 21:06 +0200
  Re: how to use volatile key word? David Brown <david@westcontrol.removethisbit.com> - 2012-06-27 09:08 +0200
    Re: how to use volatile key word? Tim Wescott <tim@seemywebsite.com> - 2012-06-27 11:10 -0500
  Re: how to use volatile key word? Tim Rentsch <txr@alumni.caltech.edu> - 2012-06-27 10:28 -0700

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