Eric Blake <ebl...@redhat.com> writes: > The documentation claims that alternates are useful for > allowing two types, although nothing enforces this. Meanwhile,
"two or more" Can touch up on commit. > it is silent on whether empty unions are allowed. In practice, > the generated code will compile, in part because we have a > 'void *data' branch; but attempting to visit such a type will > cause an abort(). While there's no technical reason that a > degenerate union could not be made to work, it's harder to > justify the time spent in chasing known (the current abort() > during visit) and unknown corner cases, than it would be to > just outlaw them. A future patch will probably take the > approach of forbidding them; in the meantime, we can at least > add testsuite coverage to make it obvious where things stand. > > In addition to adding tests to expose the problems, we also > need to adjust existing tests that are meant to test something > else, but which could fail for the wrong reason if we reject > degenerate alternates/unions. > > Note that empty structs are explicitly supported (for example, > right now they are the only way to specify that one branch of a > flat union adds no additional members), and empty enums are > covered by the testsuite as working (even if they do not seem > to have much use). > > Signed-off-by: Eric Blake <ebl...@redhat.com> > > --- > v6: commit message improved, rebase to earlier added tests Patch is fine.
