Re: [dpdk-dev] [PATCH v3 1/5] mk: remove combined library and related options

[Neil Horman <nhorman@tuxdriver.com>]

On Mon, Apr 13, 2015 at 01:04:52PM +0200, Thomas Monjalon wrote:
> 2015-04-13 10:52, Gonzalez Monroy, Sergio:
> > On 09/04/2015 21:34, Neil Horman wrote:
> > > On Thu, Apr 09, 2015 at 08:00:26PM +0300, Avi Kivity wrote:
> > >> On 04/09/2015 02:19 PM, Neil Horman wrote:
> > >>> On Thu, Apr 09, 2015 at 12:06:47PM +0300, Avi Kivity wrote:
> > >>>> On 04/09/2015 11:33 AM, Gonzalez Monroy, Sergio wrote:
> > >>>>> On 08/04/2015 19:26, Stephen Hemminger wrote:
> > >>>>>> On Wed,  8 Apr 2015 16:07:21 +0100
> > >>>>>> Sergio Gonzalez Monroy <sergio.gonzalez.monroy@intel.com> wrote:
> > >>>>>>
> > >>>>>>> Currently, the target/rules to build combined libraries is different
> > >>>>>>> than the one to build individual libraries.
> > >>>>>>>
> > >>>>>>> By removing the combined library option as a build configuration option
> > >>>>>>> we simplify the build pocess by having a single point for
> > >>>>>>> linking/archiving
> > >>>>>>> libraries in DPDK.
> > >>>>>>>
> > >>>>>>> This patch removes CONFIG_RTE_BUILD_COMBINE_LIB build config option and
> > >>>>>>> removes the makefiles associated with building a combined library.
> > >>>>>>>
> > >>>>>>> The CONFIG_RTE_LIBNAME config option is kept as it will be use to
> > >>>>>>> always generate a linker script that acts as a single combined library.
> > >>>>>>>
> > >>>>>>> Signed-off-by: Sergio Gonzalez Monroy
> > >>>>>>> <sergio.gonzalez.monroy@intel.com>
> > >>>>>> No. We use combined library and it greatly simplfies the application
> > >>>>>> linking process.
> > >>>>>>
> > >>>>> After all the opposition this patch had in v2, I did explain the current
> > >>>>> issues
> > >>>>> (see http://dpdk.org/ml/archives/dev/2015-March/015366.html ) and this was
> > >>>>> the agreed solution.
> > >>>>>
> > >>>>> As I mention in the cover letter (also see patch 2/5), building DPDK
> > >>>>> (after applying this patch series) will always generate a very simple
> > >>>>> linker script that behaves as a combined library.
> > >>>>> I encourage you to apply this patch series and try to build your app
> > >>>>> (which links against combined lib).
> > >>>>> Your app should build without problem unless I messed up somewhere and it
> > >>>>> needs fixing.
> > >>>> Is it possible to generate a pkgconfig file (dpdk.pc) that contains all of
> > >>>> the setting needed to compile and link with dpdk?  That will greatly
> > >>>> simplify usage.
> > >>>>
> > >>>> A linker script is just too esoteric.
> > >>>>
> > >>> Why esoteric?  We're not talking about a linker script in the sense of a binary
> > >>> layout file, we're talking about a prewritten/generated libdpdk_core.so that
> > >>> contains linker directives to include the appropriate libraries.  You link it
> > >>> just like you do any other library, but it lets you ignore how they are broken
> > >>> up.
> > >> You mean DT_NEEDED?  That's great, but it shouldn't be called a linker
> > >> script.
> > >>
> > > no, I don't mean DT_NEEDED, I mean a linker script, because thats what what
> > > sergio wrote is.
> > >
> > >>> We could certainly do a pkg-config file, but I don't think thats any more
> > >>> adventageous than this solution.
> > >> It solves more problems -- cflags etc.  Of course having the right DT_NEEDED
> > >> is a good thing regardless.
> > >>
> > > Thats a good point, pkgconfig doesn't provide that additionally.  Perhaps having
> > > both is the best solution.  As for the DT_NEEDED issues, the earlier threads
> > > ennumerated all the problems that were being found with the way the libraries
> > > were organized (circular dependencies).
> > >
> > > Neil
> > I am not entirely sure of the conclusion of this thread.
> > 
> > Are we happy with the current linker script solution as a replacement of 
> > the combined lib?
> > Do we want to provide pkg-config file in addition or instead of linker 
> > script?
> 
> Yes pkg-config should be an addition on top of shared/static split/combined
> libraries (or linker script). It should be an alternative to mk/rte.app.mk.
> 

Adding a pkg-config file I think makes lots of sense.

> > I think I will split the series as there seems to be no objections to 
> > the patches related to DT_NEEDED entries.
> > I'll post a series for DT_NEEDED entries and another series for dealing 
> > with the combined lib (once we get to an agreement).
> > 
> > Does it sound reasonable?
> 
yup
>