[MacPorts] #20531: gdal build fails if pthsem is installed

[Rainer Müller]

On 2009-08-08 02:18 , Sean Fulton wrote:
> One solution from the gdal perspective is to have a variant for  
> pthreads and requite pth.  In most cases I would accept that a variant  
> is appropriate but here I'm not so sure.  pthreads is the standard  
> library for threads, I think, in the vast majority of OSS and pthsem  
> shouldn't be overriding it.  On the other hand, the gdal port is  
> probably picking up the native OS X pthreads without being asked to.

pthreads is an essential interface on modern systems. On Mac OS X it is
directly implemented in libSystem against which most binaries have to
link anyway for the usual BSD library functions.

If I read the description for pth correctly, it is purely implemented in
user-mode and does not make use of kernel scheduling. Without using the
kernel scheduler such a library cannot take advantage of multiple
CPUs/cores. Therefore I would strongly recommend the Mac OS X provided
pthreads interface.

Rainer