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From: Boris on 13 Apr 2010 00:52
Hi,

Background: Let's say, there's a DLL - A.DLL (native code) that exports
function Foo(). Foo() calls some C-runtime library functions. Some other
native code (for example, in an EXE) calls Foo() from multiple threads.
There're 2 requirements to prevent multi-threading related problems inside
CRT:

1. A.DLL should be built using multi-threaded version of CRT;
2. Threads that call Foo() must be started via _beginthread/_beginthreadex,
but not via CreateThread().

I have a question on calling Foo() inside A.DLL from C# code: would calling
CRT functions by Foo() be still thread safe, if A.DLL was compiled/linked
with multi-threaded version of CRT and the below C# caller code was used?

public class SomeClass
{
...
[System.Runtime.InteropServices.DllImport("A.DLL")]
public static extern void Foo();
...
private void MyThreadFunc()
{
Foo();
}
private Thread m_thread;
...
static void Main()
{
...
m_thread = new Thread(new ThreadStart(this.MyThreadFunc));
...
}
}


Thanks,
Boris

From: Jeroen Mostert on 13 Apr 2010 01:02
On 2010-04-13 6:52, Boris wrote:
> Background: Let's say, there's a DLL - A.DLL (native code) that exports
> function Foo(). Foo() calls some C-runtime library functions. Some other
> native code (for example, in an EXE) calls Foo() from multiple threads.
> There're 2 requirements to prevent multi-threading related problems
> inside CRT:
>
> 1. A.DLL should be built using multi-threaded version of CRT;
> 2. Threads that call Foo() must be started via
> _beginthread/_beginthreadex, but not via CreateThread().
>
Requirement 2 is no longer really a requirement. See
http://support.microsoft.com/kb/104641/. Not using _beginthread*() causes a
small memory leak, but there are no threading problems. This is a good thing
too, because there would be no way for the CLR to call the "correct" CRT
version of _beginthread*() -- DLLs containing unmanaged code are not loaded
until functions in them are invoked, and by that point it's too late to call
_beginthread*().

--
J.
From: Boris on 13 Apr 2010 08:12
Thanks a lot!

"Jeroen Mostert" <jmostert(a)xs4all.nl> wrote in message
news:4bc3faef$0$22935$e4fe514c(a)news.xs4all.nl...
> On 2010-04-13 6:52, Boris wrote:
>> Background: Let's say, there's a DLL - A.DLL (native code) that exports
>> function Foo(). Foo() calls some C-runtime library functions. Some other
>> native code (for example, in an EXE) calls Foo() from multiple threads.
>> There're 2 requirements to prevent multi-threading related problems
>> inside CRT:
>>
>> 1. A.DLL should be built using multi-threaded version of CRT;
>> 2. Threads that call Foo() must be started via
>> _beginthread/_beginthreadex, but not via CreateThread().
>>
> Requirement 2 is no longer really a requirement. See
> http://support.microsoft.com/kb/104641/. Not using _beginthread*() causes
> a small memory leak, but there are no threading problems. This is a good
> thing too, because there would be no way for the CLR to call the "correct"
> CRT version of _beginthread*() -- DLLs containing unmanaged code are not
> loaded until functions in them are invoked, and by that point it's too
> late to call _beginthread*().
>
> --
> J.

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