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

[Thomas Monjalon <thomas.monjalon-pdR9zngts4EAvxtiuMwx3w@public.gmane.org>]

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-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org> 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-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
> >>>>>> 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.

> 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?

Yes good idea, thanks.