Sebastian Redl wrote:
Jens Seidel wrote:
On Thu, Apr 24, 2008 at 12:37:09PM +0200, Sebastian Redl wrote:
Any application that uses a precompiled Boost component probably uses other Boost components, too. As such, the
OK.
likelihood is high that upgrading Boost means recompiling the application.
Please explain this! Probably you mean that beside Boost libraries also parts of Boost are used which are provided in headers only? Now you assume that one has to recompile to gain from the header only parts? This is right but you forgot (if my assumptions are true) that there is a much more likely case:
Every Linux or *BSD distribution (and probably also Cygwin and Fink) contains Boost and applications linked against it. Now assume the Boost maintainer in this distribution wants to update Boost. With a stable ABI the maintainer just uploads a new version of Boost and that's all. Without a stable ABI the maintainer either has to keep the old Boost library (or better librar*ies* in this case) and provide just another version or the upload of a new Boost version requires a coordinated upload with all recompiled programs and libraries which depend on Boost. This is a very big mess!!!!
What I'm saying is that I believe it to be very dangerous to have your own application use Boost header-only libraries of one version and precompiled libraries that link against other versions of the header-only libraries. If components from the header-only version (say, a shared_ptr or an any) are somehow transferred between the main executable and the library, you're in great danger of crashing.
This is not anything specific to header-only libraries. Classes that are in the public API, regardless of whether the actual implementation is defined inline, or compiled in a separate object file, should not change their layout in point releases, in my opinion. - Volodya