[dpdk-dev] [PATCHv2 3/4] Makefiles: Add experimental tag check and warnings to trigger on use

[Bruce Richardson]

On Mon, Dec 11, 2017 at 07:40:43AM -0500, Neil Horman wrote:
> On Mon, Dec 11, 2017 at 11:35:57AM +0000, Bruce Richardson wrote:
> > On Fri, Dec 08, 2017 at 12:14:34PM -0500, Neil Horman wrote:
> > > Add checks during build to ensure that all symbols in the EXPERIMENTAL
> > > version map section have __experimental tags on their definitions, and
> > > enable the warnings needed to announce their use.  Also add a
> > > ALLOW_EXPERIMENTAL_FUNCTIONS variable check to allow for in-tree dpdk
> > > libraries to override those checks.
> > > 
> > > Signed-off-by: Neil Horman <nhorman at tuxdriver.com>
> > > CC: Thomas Monjalon <thomas at monjalon.net>
> > > CC: "Mcnamara, John" <john.mcnamara at intel.com>
> > > ---
> > 
> > Hi Neil,
> > 
> > if I read the patch functionality correctly, the
> > ALLOW_EXPERIMENTAL_FUNCTIONS variable simply suppresses all errors for
> > deprecated functions. However, what we really want is just to suppress
> > the errors for the experimental functions, and not any that really are
> > deprecated. While we may not have any now in DPDK, that doesn't mean it
> > might not be useful to have some in future.
> > 
> Well, they are all deprecated by the stict definition of the term, which is to
> say that their usage is discouraged/disapproved.  What I think you are saying is
> that you would like to differentiate reasons for deprecation (i.e. deprecation
> because an api is experimental, vs deprecation because an api is broken or going
> to be removed).  I'm not sure I see that we will get there anytime soon, but
> yes, that seems like it would be a good ability to add in here.
> 
> > Therefore, would an alternative scheme work where the experimental tag
> > is set to empty if the ALLOW_EXPERIMENTAL_FUNCTIONS define is set when
> > compiling?
> > 
> Yes, I think that could work.  Perhaps what we can do is modify
> ALLOW_EXPERIMENTAL_FUNCTIONS to set a CFLAGS like:
> -DSUPPRESS_EXPERIMENTAL
> 
> And use that to toggle the definition on rte_compat.h between something that
> deprecates the API call and an empty definition
> 

Yes, exactly what I was thinking, but failed to express so clearly.

Also, would the flag be best set globally when building DPDK itself,
rather than changing individual makefiles per library?