[ale] OT: dummy C++/threads question

[John Mills]

Alexander -

Thanks for the note, clear explanations, and example.

On Wed, 23 Jul 2003, Alexander Barton wrote:

> o Functions are _not_ member functions.  From your code snippet it looks 
> like you don't get the distinction.

I certainly didn't see its importance here. I am patching an example from 
MsVC++ and learning to use threads at the same time. Obviously VC++ is 
much more tolerant of loose typing (and I don't mean keystrokes!) and 
other glosses I find hazardous to robustness. I'ld rather know about the 
distinction and handle it explicitly.

> Since pthread's C function pointer can't be a C++ function or method, 
> you need the help of an intermediate launcher function.

I'll do it this way.

> extern "C" {
> //  This is a first-stage function with C linkage that calls
> //  an object's member function.
> //  ptr is a pointer to an object of class CMyClass that we're
> //  gonna invoke MyFunction() on.
> //
> static void launcher(void *ptr)
> {
>      try {
>          CMyClass *objectptr = dynamic_cast<CMyClass *>(ptr);
>          if (NULL == objectptr)
>              /* ...handle error.... */ ;
>          objectpre->MyFunction();
>      }
>      catch (...)
>      {
>          /* ...handle exception.... */ ;
>          //  Don't let exceptions unwind through launcher()
>      }
> }
> }

> //  Invoke with:
> CMyClass foo;
> foo.setArgs(....);
> int result = pthread_create(&thread, &attrs, launcher, &foo);

> PS: Don't futz around with pthread_mutex.  Go get BOOST's object 
> oriented wrappers for the pthreads library and save yourself much much 
> grief.

I'll have a look.

Best Regards, and thanks again for the tutorial comments.

 John Mills
 john.m.mills at alum.mit.edu

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