Re: [Libguestfs] [PATCH nbdkit filters-v2 2/5] Introduce filters.

On 01/19/2018 09:23 AM, Richard W.M. Jones wrote: Should we stick the useful functions in a new header <nbdkit-common.h> that both nbdkit-plugin.h and nbdkit-filter.h include? I'm worried that the games we play with NBDKIT_API_VERSION in nbdkit-plugin.h for maintaining back-compat there may someday have awkward interactions in this file. On the other hand, you're setting NBDKIT_FILTER_API_VERSION separately from NBDKIT_API_VERSION (for plugins), as we could bump one but not the other in a given nbdkit release (and if so, it makes for our next release to have PLUGIN version 2 but FILTER version 1, once filters and FUA flags settle, where the highest version in each file shares the same backend semantics). Does it ever make sense for a single .so file to call both NBDKIT_REGISTER_PLUGIN() and NBDKIT_REGISTER_FILTER() in the same library? If not, one benefit of having the common code in a separate nbdkit-common.h is that we could do things like: nbdkit-common.h: #if !defined NBDKIT_PLUGIN_H || !defined NBDKIT_FILTER_H #error this file should not be directly included #endif nbdkit-plugin.h: #ifdef NBDKIT_FILTER_H #error cannot mix filter and plugin in one code base #endif nbdkit-filter.h: #ifdef NBDKIT_PLUGIN_H #error cannot mix filter and plugin in one code base #endif and a common header would be a nicer place for things like NBDKIT_CXX_LANG_C, rather than having to repeat our #ifndef definitions in two files. -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3266 Virtualization: qemu.org | libvirt.org