Multithreaded Windows service in MingW

Question

I am trying to build a Windows service with MingW. It need thread safe exceptions, so I added the linker flag -mthreads. The application works fine from the command-line, but when I try to start it from services.msc, the 1054 error ("The service did not respond to the start or control request in a timely fashion") is raised. The service starts if I re-build it without the -mthreads flag. How can I get this working with -mthreads?

Answer 1

I suspect -mthreads is bringing in a dependency on a DLL, and that DLL is not on the path when it's running as a service. In my cygwin environment, if I compile a trivial program with "-mno-cygwin -mthreads", I get a dependency on MINGWM10.DLL, which certainly wouldn't be on the path when running as a service. If I try running it with no PATH set, it crashes as it starts to load (and leaves a turd in the Application event log).

I'd be bringing up your exe in Dependency Walker (http://www.dependencywalker.com) to see what you're loading at load-time, and check your Windows Event Log to see if there are any hints there. You're probably going to need to put a copy of the DLLs it needs alongside the executable.

Answer 2

You need mingwm10.dll in the working directory or in [edit: system, not per user] PATH, because C++ programs compiled with -mthread option have that dependency. If you're pretty sure exception will never be thrown by your code nor propogate through your stack, use -fno-exception instead of -mthread to resolve the dependency.

Answer 3

I wonder if you can debug it when it runs as a service. There must be something spooking your program when service host runs it. Perhaps try to attach a debugger to svchost.exe, at least you can see what modules are loaded and maybe which exception causes the crash.