[fpc-devel] how to get same pthreads code to compile between Linux and FreeBSD

[Graeme Geldenhuys]

Hi,

I initially posted this in the fpc-pascal list, but I think fpc-devel is
maybe more appropriate, because the pthreads include files might need
amendment.


I'm trying to get tiOPF to compile under FreeBSD. It works under Linux
and Windows without problems.

I got compiler errors using FPC 2.6.0 under FreeBSD, saying that the
compiler couldn't decide which version of the sem_* methods to use.

I had code like this in tiOPF:

    {$IFDEF MSWINDOWS}
    FSemaphore: THandle;
    {$ENDIF MSWINDOWS}
    {$IFDEF UNIX}
    FSemaphore: TSemaphore;
    {$ENDIF UNIX}
...

procedure TtiPool.CreatePoolSemaphore;
begin
  {$IFDEF MSWINDOWS}
  if FSemaphore <> 0 then
    CloseHandle(FSemaphore);
  FSemaphore := CreateSemaphore(nil, FMaxPoolSize, FMaxPoolSize, nil);
  {$ENDIF MSWINDOWS}
  {$IFDEF UNIX}
  FillChar(FSemaphore, sizeof(FSemaphore), 0);
  // pShared = 0 means, shared between the threads of a process
  writeln('FMaxPoolSize = ', FMaxPoolSize);
  if sem_init(@FSemaphore, 0, FMaxPoolSize) <> 0 then
    raise EtiOPFInternalException.Create('Failed to initialize the
semaphore');
  {$ENDIF UNIX}
end;

Note the sem_init() call takes a pointer.


As you can see from the quoted code below, FreeBSD has two versions of
the sem_* methods. The compiler couldn't decide which version to use:

  Error: Can't determine which overloaded function to call

To get it to compiler under FreeBSD, I must change the sem_init() line
too the following...

  if sem_init(FSemaphore, 0, FMaxPoolSize) <> 0 then

...but this breaks compiling under Linux again.


1) How do I get the tiOPF code to work under both Linux and FreeBSD
using a single {$IFDEF UNIX}. I don't really want to introduce {$IFDEF
LINUX} and {$IFDEF FREEBSD} in the code.

2) Why does FreeBSD have two versions of these methods and Linux only
one? I had a look at the other pthr*.inc units. Linux and SunOS has a
single version, BSD (which I believe is MacOSX too) and Haiku has two
versions.


----------------[ pthrbsd.inc  freebsd ]-------------------
  function sem_init(__sem:Psem_t;
__pshared:cint;__value:dword):cint;cdecl; external;
  function sem_destroy(__sem:Psem_t):cint;cdecl;external ;
  function sem_close(__sem:Psem_t):cint;cdecl;external ;
  function sem_unlink(__name:Pchar):cint;cdecl;external ;
  function sem_wait(__sem:Psem_t):cint;cdecl;external ;
  function sem_trywait(__sem:Psem_t):cint;cdecl;external ;
  function sem_post(__sem:Psem_t):cint;cdecl;external ;
  function sem_getvalue(__sem:Psem_t; __sval:Pcint):cint;cdecl;external;

  function sem_init(var __sem: sem_t; __pshared:cint;
__value:dword):cint cdecl;external;
  function sem_destroy(var __sem: sem_t):cint;cdecl;external;
  function sem_close(var __sem: sem_t):cint;cdecl;external;
  function sem_wait(var __sem: sem_t):cint;cdecl;external;
  function sem_trywait(var __sem: sem_t):cint;cdecl;external;
  function sem_post(var __sem: sem_t):cint;cdecl;external;
  function sem_getvalue(var __sem: sem_t; var
__sval:cint):cint;cdecl;external;
--------------------[ end ]----------------------

-------------------[ pthrlinux.inc   linux ]---------------------
  function sem_init(__sem:Psem_t; __pshared:cint;
__value:dword):cint;cdecl;external libthreads;
  function sem_destroy(__sem:Psem_t):cint;cdecl;external libthreads;
  function sem_close(__sem:Psem_t):cint;cdecl;external libthreads;
  function sem_unlink(__name:Pchar):cint;cdecl;external libthreads;
  function sem_wait(__sem:Psem_t):cint;cdecl;external libthreads;
  function sem_trywait(__sem:Psem_t):cint;cdecl;external libthreads;
  function sem_post(__sem:Psem_t):cint;cdecl;external libthreads;
  function sem_getvalue(__sem:Psem_t; __sval:pcint):cint;cdecl;external
libthreads;
  function sem_timedwait(__sem: Psem_t; __abstime:
Ptimespec):cint;cdecl; external libthreads;
-------------------[ end ]-----------------------


Attached is a small test project using snippets of code that tiOPF uses.
The current version of this test project will compiler under FreeBSD,
but will not compiler under Linux.


Regards,
  - Graeme -

-- 
fpGUI Toolkit - a cross-platform GUI toolkit using Free Pascal
http://fpgui.sourceforge.net/




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