[Libguestfs] [PATCH libnbd v3 0/6] Additional non-NULL warnings, checks and docs

v2: https://listman.redhat.com/archives/libguestfs/2022-September/030014.html I didn't think this would need a v3, but here we are. The first patch (also a new patch) appears to fix a bug in Eric's earlier series to do with meta queries. It's not possible to call the new APIs with queries == NULL, and this becomes obvious when you use attribute((nonnull)) and enable GCC warnings. I tried to fix this, but two tests still fail for reasons I'm not clear about: FAIL: opt-list-meta-queries FAIL: opt-set-meta-queries The third patch is also new, and extends attribute((nonnull)) annotations to many internal functions. No actual errors found by this, but it seems worth it to avoid future problems, assuming that GCC won't start adding undefined behaviour. I wonder aloud if we should only enable attribute((nonnull)) for developer builds, ie. tie it to ./configure --enable-gcc-warnings somehow. (This series does not do this.) I added comments as suggested by Laszlo to patch 2, and picked up his R-b's and Acks. Rich.