CRT thread-safe when called from C-Sharp
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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. |