[reSIProcate] [reSIProcate-commit] resiprocate 8871 sgodin: -fixed potential multi-threading issues with static member variable initialization

[Scott Godin]

Hi Kennard,

Static member variables are constructed the first time the function is
called.  If multiple threads call a particular member function (that
contains a static variable) for the first time at the exact same time (ie.
thread preempts in the middle of object construction), then both threads can
end up trying to construct the same static object.  I was seeing this
behaviour under Visual Studio 2008, it possible that this problem does not
exist on other compilers.  Moving the static variables outside of the member
function causes them to be created when the application is initialized, thus
avoiding this race.

Scott

On Wed, Dec 1, 2010 at 1:00 PM, Kennard White <kennard_white at logitech.com>wrote:

> Hi Scott,
>
> There is some intricacy of C++ that I don't understand. Could you explain
> the thread safety issue below? Is there a difference in when the
> constructors/destructors are called?
>
> Thanks,
> Kennard
>
> +static const Data errorContextData("Contents");
>  const Data&
>  Contents::errorContext() const
>  {
> -   static const Data context("Contents");
> -   return context;
> +   return errorContextData;
>  }
>
>
> On Sat, Nov 27, 2010 at 7:37 AM, <svn at resiprocate.org> wrote:
>
>>  Projectresiprocate New Revision8871<http://svn.resiprocate.org/viewsvn/resiprocate?view=rev&rev=8871>
>> Committersgodin (Scott Godin) Date2010-11-27 09:37:49 -0600 (Sat, 27 Nov
>> 2010) Log
>>
>>  -fixed potential multi-threading issues with static member variable initialization
>>  -expose resip local logger id to applications
>>
>>
>>
>>
>> Modified:
>>
>>    - main/resip/dum/UserProfile.cxx
>>    <http://svn.resiprocate.org/viewsvn/resiprocate/main/resip/dum/UserProfile.cxx?r1=8870&r2=8871&diff_format=l>
>>    - main/resip/stack/Contents.cxx
>>    <http://svn.resiprocate.org/viewsvn/resiprocate/main/resip/stack/Contents.cxx?r1=8870&r2=8871&diff_format=l>
>>    - main/resip/stack/DnsInterface.cxx
>>    <http://svn.resiprocate.org/viewsvn/resiprocate/main/resip/stack/DnsInterface.cxx?r1=8870&r2=8871&diff_format=l>
>>    - main/resip/stack/DnsResult.cxx
>>    <http://svn.resiprocate.org/viewsvn/resiprocate/main/resip/stack/DnsResult.cxx?r1=8870&r2=8871&diff_format=l>
>>    - main/resip/stack/SdpContents.cxx
>>    <http://svn.resiprocate.org/viewsvn/resiprocate/main/resip/stack/SdpContents.cxx?r1=8870&r2=8871&diff_format=l>
>>    - main/resip/stack/SipMessage.cxx
>>    <http://svn.resiprocate.org/viewsvn/resiprocate/main/resip/stack/SipMessage.cxx?r1=8870&r2=8871&diff_format=l>
>>    - main/resip/stack/Tuple.cxx
>>    <http://svn.resiprocate.org/viewsvn/resiprocate/main/resip/stack/Tuple.cxx?r1=8870&r2=8871&diff_format=l>
>>    - main/resip/stack/Uri.cxx
>>    <http://svn.resiprocate.org/viewsvn/resiprocate/main/resip/stack/Uri.cxx?r1=8870&r2=8871&diff_format=l>
>>    - main/resip/stack/XMLCursor.cxx
>>    <http://svn.resiprocate.org/viewsvn/resiprocate/main/resip/stack/XMLCursor.cxx?r1=8870&r2=8871&diff_format=l>
>>    - main/resip/stack/ssl/Security.cxx
>>    <http://svn.resiprocate.org/viewsvn/resiprocate/main/resip/stack/ssl/Security.cxx?r1=8870&r2=8871&diff_format=l>
>>    - main/resip/stack/ssl/WinSecurity.cxx
>>    <http://svn.resiprocate.org/viewsvn/resiprocate/main/resip/stack/ssl/WinSecurity.cxx?r1=8870&r2=8871&diff_format=l>
>>    - main/rutil/Log.hxx
>>    <http://svn.resiprocate.org/viewsvn/resiprocate/main/rutil/Log.hxx?r1=8870&r2=8871&diff_format=l>
>>
>>
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>>
>
>
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