Re: [dpdk-dev] [PATCH v2 02/10] meson: add BUILDING_RTE_SDK

[Bruce Richardson <bruce.richardson@intel.com>]

On Wed, Jun 19, 2019 at 02:34:43PM -0400, Neil Horman wrote:
> On Wed, Jun 19, 2019 at 11:46:12AM +0100, Bruce Richardson wrote:
> > On Wed, Jun 19, 2019 at 06:39:00AM -0400, Neil Horman wrote:
> > > On Thu, Jun 13, 2019 at 03:44:02PM +0100, Bruce Richardson wrote:
> > > > On Thu, Jun 13, 2019 at 10:23:36AM -0400, Neil Horman wrote:
> > > > > The __rte_internal macro is defined dependent on the value of the build
> > > > > environment variable BUILDING_RTE_SDK.  This variable was set in the
> > > > > Makefile environment but not the meson environment, so lets reconcile
> > > > > the two by defining it for meson in the lib and drivers directories, but
> > > > > not the examples/apps directories, which should be treated as they are
> > > > > not part of the core DPDK library
> > > > > 
> > > > > Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
> > > > > CC: Jerin Jacob Kollanukkaran <jerinj@marvell.com>
> > > > > CC: Bruce Richardson <bruce.richardson@intel.com>
> > > > > CC: Thomas Monjalon <thomas@monjalon.net>
> > > > > ---
> > > > >  drivers/meson.build | 1 +
> > > > >  lib/meson.build     | 1 +
> > > > >  2 files changed, 2 insertions(+)
> > > > > 
> > > > > diff --git a/drivers/meson.build b/drivers/meson.build
> > > > > index 4c444f495..a312277d1 100644
> > > > > --- a/drivers/meson.build
> > > > > +++ b/drivers/meson.build
> > > > > @@ -23,6 +23,7 @@ endif
> > > > >  
> > > > >  # specify -D_GNU_SOURCE unconditionally
> > > > >  default_cflags += '-D_GNU_SOURCE'
> > > > > +default_cflags += '-DBUILDING_RTE_SDK'
> > > > >  
> > > > >  foreach class:dpdk_driver_classes
> > > > >  	drivers = []
> > > > > diff --git a/lib/meson.build b/lib/meson.build
> > > > > index e067ce5ea..0e398d534 100644
> > > > > --- a/lib/meson.build
> > > > > +++ b/lib/meson.build
> > > > > @@ -35,6 +35,7 @@ if is_windows
> > > > >  endif
> > > > >  
> > > > >  default_cflags = machine_args
> > > > > +default_cflags += '-DBUILDING_RTE_SDK'
> > > > >  if cc.has_argument('-Wno-format-truncation')
> > > > >  	default_cflags += '-Wno-format-truncation'
> > > > >  endif
> > > > 
> > > > While this will work, it's not something that individual components should
> > > > ever need to override so I think using "add_project_arguments()" function
> > > > is a better way to add this to the C builds.
> > > > 
> > > That sounds like it makes sense to me, but reading the documentation for meson,
> > > I'm not sure I see the behavioral difference.  Can you elaborate on how
> > > add_project_arguments behaves differently here?
> > > 
> > The end result should be the same. The key differences are:
> > 1. Only ever needs to be set in one place
> > 2. Cannot be overridden by the individual objects in the build.
> > 
> > So it's just slightly cleaner. If you prefer your existing approach, I'm ok
> > with that.
> > 
> 
> No, I like the aspect of item 2, though, just for clarification, do we really
> only need to set it at the top level?  I ask because it seems that
> BUILDING_RTE_SDK should be set for the lib and drivers subtrees, but not the app
> subtree, as that tree, being the location of our example code, should be treated
> as non-core dpdk libraries, and so should throw an error if any code there
> attempts to use a dpdk internal only function.  Or is there some other magic
> afoot in that subtree?
> 
Good point. Keep your original patch as-is so.

/Bruce