[dpdk-dev] [PATCH v5 04/17] build: define _GNU_SOURCE globally

[Thomas Monjalon]

26/02/2021 10:46, Bruce Richardson:
> On Fri, Feb 26, 2021 at 10:40:32AM +0100, Thomas Monjalon wrote:
> > 26/02/2021 10:08, Bruce Richardson:
> > > On Thu, Feb 25, 2021 at 07:22:37PM +0100, Thomas Monjalon wrote:
> > > > There was an intent to define _GNU_SOURCE globally,
> > > > but it was not set in pkg-config for external applications.
> > > > 
> > > Is this something that we really want to do, to force all external apps to
> > > use _GNU_SOURCE when compiling? Do some of our header files rely on
> > > definitions only available with _GNU_SOURCE? If so, we should probably look
> > > to remove that dependency rather than mandating the define.
> > 
> > From patch 5:
> > In musl libc, cpu_set_t is defined only if _GNU_SOURCE is defined.
> > 
> > If we avoid mandating _GNU_SOURCE,
> > we must #ifdef functions relying on rte_cpuset_t in the headers:
> > 	- rte_lcore_cpuset
> > 	- rte_thread_set_affinity
> > 	- rte_thread_get_affinity
> > 	- rte_telemetry_init (internal)
> > Or a different trick in linux/include/rte_os.h could be:
> > 	typedef void rte_cpuset_t;
> > so it allows including files, but not using above functions of course.
> > 
> Can we just define _GNU_SOURCE in the header file with rte_cpuset_t?

That would be the simplest solution yes :)
I don't really like defining such flag in a header file because
it impacts all code coming after the include.
It would mean all includes done after DPDK ones behave differently.

I vote for the trick:
#ifdef _GNU_SOURCE
	typedef cpu_set_t rte_cpuset_t;
#else
	typedef void rte_cpuset_t;
#endif

Opinions?