Re: Initialization of local statics
Paavo Helde wrote:
Marcel M?ller <news.5.maazl@spamgourmet.org> wrote in news:4c9f442d$0
$6974$9b4e6d93@newsspool4.arcor-online.net:
static const A& foo()
{ puts("foo()");
static const A var;
return var;
}
[...]
If this is not thread safe one could never store non POD constants in
local statics in a multi threaded application, even if the underlying
object type provides thread safety for const methods, isn't it?
For making this thread-safe there is a simple approach not involving any
locking: just make sure that any such function is called at least once in
the beginning of main(), before any extra threads are created. This
assumes of course that no threads are created directly or indirectly
from constructors of static objects.
Well, it might be not that simple to call a member function deep in the
business logic without even having an object of the appropriate type.
Furthermore if there is no need for delayed initialization, you could
simply move the static object outside the method implementation in the
compilation unit to achieve the same automatically. But then we are
talking about the static initialization hell.
Note that there is a similar rule for program shutdown: one should take
care that all created threads are properly joined before program exit, so
the statics are destroyed in single-threaded mode.
Never heard of that. But of course, it is straight forward to do so.
Calling exit() with several active threads makes no sense anyway.
Depending on the platform the result is completely different. WinXX
AFAIK ends the application not before the last thread died. OS/2
implicitly cancels all threads unconditional if thread 1 dies.
Marcel