Re: [Boost-users] [thread] safe portable static mutex initialization

Subject: Re: [Boost-users] [thread] safe portable static mutex initialization
From: Dave Abrahams (dave_at_[hidden])
Date: 2012-04-20 09:41:43

on Fri Apr 20 2012, Will Mason <willchido-AT-gmail.com> wrote:

> Hello,
>
> On Fri, Apr 20, 2012 at 8:04 AM, Juan Ramírez <juanantonio.ram_at_[hidden]> wrote:
>
>     It's not related to the user type, neither to mutex initialization,
>     it's related to variable initialization in general.
>     
>     A global static variable is guaranteed to be initialized before usage.

If you truly mean "static," such that it's not visible outside its
translation unit, that is correct.

>     But the initialization of static variables declared inside a function
>     is not guaranteed to be thread safe. So you could easily end up
>     calling it's constructor twice.
>
> That's something that boost::call_once is good at preventing.

Correct, for C++03.  I could be mis-remembering but IIRC in C++11
function-local static variables have been given automatic threadsafe
initialization.

-- 
Dave Abrahams
BoostPro Computing
http://www.boostpro.com