Re: mt questions

[Pascal J. B. <pj...@in...>]

shashank <sha...@gm...> writes:

>>> 5.  In [xthread.d, line 99,152] what does #define
> THREADPROC_SIGNATURE do?
>> This is just a syntax sugar to hide win32/posix thread function
> return type.
> Can you elaborate more?


Use: M-x grep RET C-a C-k grep -nH THREADPROC_SIGNATURE *.d RET

It is defined in two #ifdef:

    #if defined(POSIX_THREADS)
    // ...
    #define THREADPROC_SIGNATURE void *
    // ...
    #endif  /* POSIX*_THREADS */

    #if defined(WIN32_THREADS)
    // ...
    #define THREADPROC_SIGNATURE unsigned WINAPI
    // ...
    #endif  /* WIN32_THREADS */



It is used in two functions:

    local THREADPROC_SIGNATURE thread_stub(void *arg)
    local THREADPROC_SIGNATURE mt_main_actions (void *param)


So when we use POSIX_THREADS, those two functions will have the
signature:

    local void * thread_stub(void *arg)
    local void * mt_main_actions (void *param)

returning a pointer, 

but when we use WIN32_THREADS, they will have the signature:

    local unsigned WINAPI thread_stub(void *arg)
    local unsigned WINAPI mt_main_actions (void *param)

returning a unsigned.

This is the basic substitution mechanism of C pre-processor macros.


What we've done here, is to conditionnalize the return type depending on
the kind of threads we use.


Similarly, the other xthread_* macros are defined differently depending
on the kind of thread we use, so that we can write a single source text,
that will be processed and produce a different source program depending
on the kind of thread we use.


-- 
__Pascal Bourguignon__
http://www.informatimago.com/
"Le mercure monte ?  C'est le moment d'acheter !"