On Wed, Sep 13, 2006 at 01:34:34PM -0700, walt wrote: > The basic problem is whether an OS uses libpthread or libc_r > for the threading library. Unfortunately, I have no idea why > developers choose one over the other -- maybe someone here could > 'splain it to us? I get the feeling that there is a lot of > history involved in this story.
The basic problem you should be aware of is that loading a thread library as dependency only works during the initial linking. This is quite easy to understand when looking e.g. at the stdio locking inside libc, which is reduced to a nop otherwise. FreeBSD 4 originally shipped libc_r with included libc and we inherited that until it was fixed shortly after 1.2 (I think, haven't verified). For the very same reason, libtool explicitly drops libc_r from shared object creation calls. -pthread is handled slightly different -- it is recorded, but doesn't directly affect the linkage. A library can be used without linking the main program with -pthread as long as they don't call pthread_create. The patch replaces the hard-coded detection magic with a test for the *known* values in pkgsrc, but that's of course not portable and upstream ready. Testing for -pthread as thread linkage option is a good thing in general though, since it works on a lot of systems. Joerg
