[HarfBuzz] compilation error of 0.9.26 with MinGW

[Werner LEMBERG]

>> hb-common.cc: In function 'hb_language_item_t* lang_find_or_insert(const char*)':
>> hb-atomic-private.hh:61:47: error: expected primary-expression before ')' token
>>  #define hb_atomic_ptr_get(P)  (MemoryBarrier (), (void *) *(P))
>
> Interesting.  Can you try the attached patch?  Looks like a MinGW
> bug to me.

It seems to be a bug in MinGW, see

  https://sourceforge.net/p/mingw/bugs/2131/
  https://sourceforge.net/p/mingw/bugs/2181/

Maybe you can add comments there, if necessary.

Applying the recommended fix from those two bug reports, however,
fails for me; macro expansion then reduces

  hb_language_item_t *first_lang =
    (hb_language_item_t *) hb_atomic_ptr_get (&langs);

to

  hb_language_item_t *first_lang =
    (hb_language_item_t *) (, (void *)&langs)

which the compiler still doesn't like.

Running MinGW natively on a Win7 box, I admit that I have no idea why
MinGW expands to the fallback macro, which is empty – maybe you have
to explicitly define the Windows version (via the _WIN32_WINNT macro)
to be something equal to or newer than Vista?  On the other hand, I
think that the original HarfBuzz code isn't correct either, since it
relies on the fact that `MemoryBarrier' always expands to a function
call, which is obviously not true.

The good news: Your patch works :-)  To avoid warnings, you should
insert

  # undef MemoryBarrier

before (re)defining `MemoryBarrier'.


    Werner