Re: [dpdk-dev] [PATCH v2 00/19] ensure headers have correct includes

[Thomas Monjalon <thomas@monjalon.net>]

21/01/2021 16:15, Bruce Richardson:
> On Thu, Jan 21, 2021 at 10:36:18AM +0100, Thomas Monjalon wrote:
> > 21/01/2021 10:33, Bruce Richardson:
> > > On Thu, Jan 21, 2021 at 10:25:07AM +0100, David Marchand wrote:
> > > > Is rte_byteorder.h inclusion in rte_mbuf.h still necessary?
> > > >
> > > Good question. The checks I was doing were only for missing headers.
> > > Checking for superfluous headers is more complicated and not something I've
> > > looked at. I know it was previously suggested to use the
> > > "include-what-you-use" tool on DPDK, if anyone wants to attempt that.
> > 
> > I would love having an integration of include-what-you-use in our build system.
> > I don't know whether it's trivial or difficult with meson.
> > 
> 
> Did some initial investigation here, and here are some basic instructions
> based on how I got it running on my Ubuntu 20.10 system. The positive is
> that "iwyu_tool" can run on DPDK build dirs without any extra work on our
> part.

I had looked at it recently but didn't try thinking meson was not compatible.
Thank you, it works :)

> 1. Install iwyu from Ubuntu packaging.
> 2. Install clang-9 package:
> 	* This is not a dependency of iwyu, but probably should be
> 	* The version of clang installed *must* match that used to build iwyu
> 	  [I had clang-10 installed which didn't work for this]
> 	* If you get errors about missing standard headers e.g. stddef.h,
> 	  the version mismatch is likely the issue.
> 3. Configure a clang build of DPDK:
> 	* CC=clang meson <args> build-clang
> 4. "iwyu_tool" supports the build database format used by meson, so just
>    run: "iwyu_tool -p build-clang"
> 
> Be warned, this runs really slowly and produces lots of output!

We need to filter only reports of useless includes
and do the cleaning...

The difficult part is that some includes may be useless on Linux
but required on FreeBSD.