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

[Neil Horman <nhorman@tuxdriver.com>]

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