Re: [dpdk-dev] [PATCH v3] compat: merge compat library into EAL

[Neil Horman <nhorman@tuxdriver.com>]

On Wed, Feb 06, 2019 at 02:17:45PM +0000, Bruce Richardson wrote:
> On Wed, Feb 06, 2019 at 07:22:54AM -0500, Neil Horman wrote:
> > On Wed, Feb 06, 2019 at 11:01:30AM +0000, Bruce Richardson wrote:
> > > Since compat library is only a single header, we can easily move it into
> > > the EAL common headers instead of tracking it separately. The downside of
> > > this is that it becomes a little more difficult to have any libs that are
> > > built before EAL depend on it. Thankfully, this is not a major problem as
> > > the only library which uses rte_compat.h and is built before EAL (kvargs)
> > > already has the path to the compat.h header file explicitly called out as
> > > an include path.
> > > 
> > > However, to ensure that we don't hit problems later with this, we can add
> > > EAL common headers folder to the global include list in the meson build
> > > which means that all common headers can be safely used by all libraries, no
> > > matter what their build order.
> > > 
> > This assumes that the compat lib will always just be a header though, no?  Will
> > this work in the event that someone wants to add some compatibility code that
> > requires its own C compilation unit?
> > 
> 
> No, it probably won't work, you'll hit an issue with any libraries that
> don't depend on EAL and need that functionality. The question is whether
> this is likely to be an issue in the future for us. I'd say the possiblity
> is fairly remote, but I'm open to input on it.
> 
Im afraid I don't have any more visibility on that than anyone else.  The fact
that it hasn't been needed yet is likely a good sign, but I am concerned at the
notion that this change enjoins us from having that flexibility.

> > > As a side-effect, this patch also fixes an issue with building on BSD using
> > > meson, due to compat lib no longer needing to be listed as a dependency.
> > > 
> > Can you elaborate here a bit please?  listing a lib as a dependency seems like a
> > fundamental function of a build system, was there a bug with meson in this
> > capacity?
> > 
> 
> It was a bug in DPDK. There was already a dependency on the compat
> library from libeal from linux, but not from BSD, so when a further
> dependency was added globally, the BSD build broke, but the linux one
> didn't.
> 
Do you have a link to the breakage details?  I'd like to look at it to see if
there is a way around this without enjoining us from adding compat C files in
the future.

Thanks
Neil

> /Bruce
>