Re: [boost] Re: Problematic inclusion of "pthread.h".

From: Christoph Ludwig (cludwig_at_[hidden])
Date: 2004-10-05 11:22:39

On Tue, Oct 05, 2004 at 06:05:54PM +0200, Markus Schöpflin wrote:
> John Maddock wrote:
> 
[...]
> >I think on some platforms <pthread.h> doesn't compile unless _REENTRANT 
> >or some similar compiler-specific magic symbol is defined: in other 
> >words it's an assert that the compiler is indeed in thread safe mode.
> 
> Yes, it's true. _REENTRANT has to be defined, there is an explicit check in 
> "pthread.h" for this.
> 
> >It looks to me as though BOOST_HAS_THREADS is getting set 
> >unconditionally for gcc on this platform, and presumably we should only 
> >set it when _REENTRANT is defined (I'm assuming that's the symbol that 
> >gets defined when the -thread option is used - can you check?).
> >
> >Hold on... checked the output from config_info and looks as though 
> >_REENTRANT *is* defined, so I'm mystified.  I also note that the 
> >platform is detected as "generic unix".  Do you know what macros gcc 
> >defines to identify this platform?
> 
> Attached is the output of "gcc -ansi -dM". I hope it contains enough 
> information to answer your questions. Note also that _REENTRANT is not 
> defined here, therefore its source must be somewhere outside of gcc.

_REENTRANT is most likely be set by libstdc++-v3. 

IIRC, the standard library that ships with gcc 3.4.x defines it, e.g.,
in (some file included by) string.h, no matter whether you provided
`-pthread' (or `-thread' on your platform) or not. 

string.h is included by config_info.cpp whence config_info reports
_REENTRANT as set.

Regards

Christoph

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