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

[Sean Fulton]

On 7 Aug, 2009, at 7:35 PM, Ryan Schmidt wrote:

>
> On Aug 7, 2009, at 08:50, Sean Fulton wrote:
>
>> On Sun, Aug 2, 2009 at 10:24 PM, MacPorts wrote:
>>
>>> #20531: gdal build fails if pthsem is installed
>>
>> Does pthsem replace pth entirely?
>
> I have no idea what pthsem even is. I just happened to have it  
> installed due to some previous port testing, and then noticed gdal  
> failed to build.
>


pthsem is pth + semaphores.  Semaphores are used is parallel  
programming.   The gdal port builds with pthreads  if they are  
available but doesn't explicitly check for pth or pthsem.  gdal  
doesn't really have any knowledge of pthsem.  pthsem usually is  
installed alongside pth and only used if the compiler asks for it.  If  
pthsem is overriding pth, that could be a problem with pthsem.

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.

Should a port that wants threading stick to explicitly requesting  
MacPorts pth?  How much can/should a port take in the OS  libraries?

   Sean