Re: [PATCH v7 4/4] eal: add nonnull and access function attributes

[David Marchand <david.marchand@redhat.com>]

On Wed, Feb 1, 2023 at 2:16 PM Thomas Monjalon <thomas@monjalon.net> wrote:
> > > I tend to prefer this kind of namespace as well.
> > > Let's compare different naming proposals,
> > > taking into account what we already have for some annotations,
> > > and what is proposed to be added in this patch and David's patch
> > > for lock annotations.
> >
> > David's lock annotations don't use a dedicated naming convention, but simply replaces __attribute__(name(params)) with __rte_name(params), e.g.:
> >
> > #define __rte_guarded_by(...) \
> >       __attribute__((guarded_by(__VA_ARGS__)))
> > #define __rte_exclusive_locks_required(...) \
> >       __attribute__((exclusive_locks_required(__VA_ARGS__)))
> > #define __rte_assert_exclusive_lock(...) \
> >       __attribute__((assert_exclusive_lock(__VA_ARGS__)))
> >
> > This follows the existing convention in rte_common.h, which is easily readable, because they directly translate to GCC attribute names, e.g.:
> >
> > #define __rte_warn_unused_result __attribute__((warn_unused_result))
> > #define __rte_always_inline inline __attribute__((always_inline))
> > #define __rte_noinline __attribute__((noinline))
> > #define __rte_hot __attribute__((hot))
> > #define __rte_cold __attribute__((cold))
> >
> > I could follow this convention too, e.g.:
> >
> > #define __rte_nonnull(...) __attribute__((nonnull(__VA_ARGS__)))
> >
> > #define __rte_access_read_only(...) \
> >       __attribute__((access(read_only, __VA_ARGS__)))
> > #define __rte_access_write_only(...) \
> >       __attribute__((access(write_only, __VA_ARGS__)))
> >
> [...]
> > > Longer macro names may be better for code readers.
> >
> > You have a good point here, Thomas. It will also prevent using the access mode attribute macros incorrectly.
> >
> > Let's proceed with two macros (without and with size parameter) instead of the combined macros (with optional size parameter).
> >
> > Referring to the existing convention in rte_common.h, what do you think about naming the new macros as follows?
> >
> > __rte_access_read_only(ptr_index)
> > __rte_access_read_only_size(ptr_index, size_index)
> >
> > Or just:
> >
> > __rte_read_only(ptr_index)
> > __rte_read_only_size(ptr_index, size_index)
>
> I think we don't need the word "access", so I prefer the second form.
>
> What about the proposal of having "param" in the name?
> We could also have "function" is some macro names.
> Does it bring a benefit?
>
> Please let's have a naming discussion with many opinions.

Thomas, I think naming convention/discussion is the most likely to
never conclude.

Just copying my previous suggestion.
__rte_read_only_params(indexes...)
__rte_write_only_params(indexes...)
__rte_no_access_params(indexes...)

So if we are not going with the existing (kind of) convention to just
prefix with __rte_, I prefer Morten second form too and I have no
better idea.


As for the lock annotations series, if you are not confident with the
form I went with, I don't mind deferring to a later release.
Though it adds more work on my pile like rebasing the vhost library.
Additionnally, we lose the opportunity to catch introduction of new
lock issues in the dpdk tree.


-- 
David Marchand