Wow, that's a hard line you've drawn there. I'm not sure I agree. The only reason this matters is if you're going to be changing the implementation and don't want to recompile the code that uses the header. For users compilation time matters as well. Users who don't use
Anthony Williams wrote: precompiled headers have to recompile a header only library over and over.
For boost users, the implementation only changes if they change boost versions, and in that case I would expect people to recompile anyway --- I wouldn't trust something compiled against boost 1.37 to link against a 1.38 lib, for example.
In any case, after further thought I remembered the reason I didn't do this before. If the exceptions are header-only then they cannot be thrown from a DLL and caught outside the DLL, since the type-ids won't match. This would mean that any exceptions thrown by the DLL version of boost.thread wouldn't be able to be caught in user code other than by catching std::exception or with catch(...). This is the case for MSVC/Windows anyway --- I'm not sure about other compilers/platforms.
I could change the code so that if you're linking against the static library then the exception functions are inline, since they can't be thrown across DLL boundaries anyway in this case. That would mean that if you were static linking against boost.thread then you wouldn't actually need the lib in some cases (e.g. if all you used was boost::mutex).
Anthony