[Saga-devel] saga SVN commit 3324: /trunk/saga/saga/adaptors/utils/

[Hartmut Kaiser]

> User: amerzky
> Date: 2009/01/17 10:37 AM
> 
> Modified:
>  /trunk/saga/saga/adaptors/utils/
>   utils.cpp
> 
> Log:
>  don't optimize - C++ static initialization and threads  don't go
>  along very well it seems

Thread safe initializations of statics is complex in any language. It's
definitely not a C++ problem. C suffers from the same subtleties. All global
data needs to be protected in multithreaded environments. And initialization
of globals in multi threaded environments is tricky to say the best.

But it is possible, you just have to know how to make it happen. Joao wrote
a nice helper class based on Boosts init_once facility for doing exactly
this
(saga/external/boost/spirit/boost/spirit/core/non_terminal/impl/static.hpp).

Regards Hartmut

BTW: you don't need the 'bool have_localhosts' anymore. As every invocation
of this functions get's its own copy of the vector anyways.


>  A
> 
> File Changes:
> 
> Directory: /trunk/saga/saga/adaptors/utils/
> ===========================================
> 
> File [modified]: utils.cpp
> Delta lines: +2 -6
> ===================================================================
> --- trunk/saga/saga/adaptors/utils/utils.cpp	2009-01-17 16:08:08 UTC
> (rev 3323)
> +++ trunk/saga/saga/adaptors/utils/utils.cpp	2009-01-17 16:37:19 UTC
> (rev 3324)
> @@ -177,14 +177,10 @@
>        // a '.' in its name.
>        std::vector <std::string> get_localhosts (void)
>        {
> -        // scoped lock, to protect the static variables
> -        boost::recursive_mutex              mtx_;
> -        boost::recursive_mutex::scoped_lock lock (mtx_);
> -
>          // optimization: build this list only once - we assume that
> host names
>          // do not change during the runtime of the SAGA application.
> -        static std::vector <std::string> localhosts;
> -        static bool have_localhosts = false;
> +        std::vector <std::string> localhosts;
> +        bool have_localhosts = false;
> 
> 
>          std::set    <std::string> initial_names;
> 
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