Re: [boost] boost.filesystem on HPUX

From: Toon Knapen (toon.knapen_at_[hidden])
Date: 2005-06-21 07:12:52

S G Ganesh wrote:

> 
>>>Yes that seems eminently reasonable (that readdir_r only be
>>>prototyped/available if -mt is supplied).
> 
> Yes, since readdir_r is specifically for multithreaded code.
> 

but it is guarded with the code below

> 
>>>Well, there is code in libs/filesystem/src/operations_posix_windows.cpp that
> 
> attempts to
> 
>>>detect if it is being compiled with multi-threading enabled:
>>>
>>>#     if defined(_POSIX_THREAD_SAFE_FUNCTIONS) \
>>>      && defined(_SC_THREAD_SAFE_FUNCTIONS) \
>>>      && (_POSIX_THREAD_SAFE_FUNCTIONS+0 >= 0)
>>>Presumably aCC sets these macros incorrectly, or this code is not
>>>correct.  Maybe the check should be for >0?
> 
> 
> They are defined in <sys/unistd.h> (but the check will fail if the header
> file is not included).

The problem seems to be that the header unistd.h is included. Apparantly 
unistd.h always defines the above tokens, even if the '-mt' flag is not 
passed on to the compiler.

I tested this in a small test-program:

<tt.cpp>
#include <unistd.h>
#include <iostream
int main() {
   std::cout << _POSIX_THREAD_SAFE_FUNCTIONS << std::endl ;
   std::cout << _SC_THREAD_SAFE_FUNCTIONS    << std::endl ;
   std::cout << _POSIX_THREAD_SAFE_FUNCTIONS << std::endl ;
   return 0 ;
}
</tt.cpp>

And 'aCC -AA tt.cpp ; ./a.out' gives :

<cout>
1
441
1
</cout>

Next 'aCC -AA -mt tt.cpp ; ./a.out' gives exactly the same output.

So it's clear that the current testing of _POSIX_THREAD_SAFE_FUNCTIONS, 
_SC_THREAD_SAFE_FUNCTIONS and _POSIX_THREAD_SAFE_FUNCTIONS does not 
suffice. Thus I still think it's best to expand the #if test to:

#     if defined(_POSIX_THREAD_SAFE_FUNCTIONS) \
         && defined(_SC_THREAD_SAFE_FUNCTIONS) \
         && (_POSIX_THREAD_SAFE_FUNCTIONS+0 >= 0) \
         && ( !defined(__HP_aCC) \
              || ( (defined(__HP_aCC) && defined(_REENTRANT) )

to make sure that, in case we're compiling with HP-aCC, we also check 
that the token _REENTRANT is defined.