Re: [dpdk-dev] [PATCH v2 1/4] mk: Remove combined library and related options

[Stefan Puiu <stefan.puiu@gmail.com>]

Hi,

2 cents from a DPDK library user - I make 2 changes to the default
linux+gcc configuration: combine libraries and build shared libraries
(since I want 2 instances of the app, it didn't make sense to me to
link statically). I tried working with the individual libs, but adding
all of them with --start-group/-end-group just seemed so much more
painful than simply linking against one lib. I know there are some
Makefile variables to help with this, but I use scons for building my
app, so that doesn't help much.

Of course, if that can be achieved easily after building all the
libraries, that's fine. But I think combining the libs makes a lot of
sense in many cases.

Thanks,
Stefan.

On Fri, Mar 13, 2015 at 3:17 PM, Neil Horman <nhorman@tuxdriver.com> wrote:
> On Fri, Mar 13, 2015 at 11:48:59AM +0000, Gonzalez Monroy, Sergio wrote:
>> On 13/03/2015 11:34, Kavanagh, Mark B wrote:
>> >>On 13/03/2015 10:49, Kavanagh, Mark B wrote:
>> >>>>---
>> >>>>config/common_bsdapp                        |   6 --
>> >>>>config/common_linuxapp                      |   6 --
>> >>>>config/defconfig_ppc_64-power8-linuxapp-gcc |   2 -
>> >>>>lib/Makefile                                |   1 -
>> >>>>mk/rte.app.mk                               |  12 ----
>> >>>>mk/rte.lib.mk                               |  35 ----------
>> >>>>mk/rte.sdkbuild.mk                          |   3 -
>> >>>>mk/rte.sharelib.mk                          | 101 ----------------------------
>> >>>>mk/rte.vars.mk                              |   9 ---
>> >>>>9 files changed, 175 deletions(-)
>> >>>>delete mode 100644 mk/rte.sharelib.mk
>> >>>>
>> >>>>diff --git a/config/common_bsdapp b/config/common_bsdapp
>> >>>>index 8ff4dc2..7ee5ecf 100644
>> >>>>--- a/config/common_bsdapp
>> >>>>+++ b/config/common_bsdapp
>> >>>>@@ -79,12 +79,6 @@ CONFIG_RTE_FORCE_INTRINSICS=n
>> >>>>CONFIG_RTE_BUILD_SHARED_LIB=n
>> >>>>
>> >>>>#
>> >>>>-# Combine to one single library
>> >>>>-#
>> >>>>-CONFIG_RTE_BUILD_COMBINE_LIBS=n
>> >>>>-CONFIG_RTE_LIBNAME=intel_dpdk
>> >>>Hi Sergio,
>> >>>
>> >>>Removing these options breaks compatibility with OVS. While it may be feasible to link
>> >>to individual static libraries, in our experience, a single combined library provides a
>> >>much more convenient way of linking.
>> >>>Thanks,
>> >>>Mark
>> >>>
>> >>>>-
>> >
>> >(snip)
>> >
>> >
>> >>>>-endif
>> >>>>-
>> >>>>-RTE_LIBNAME := $(CONFIG_RTE_LIBNAME:"%"=%)
>> >>>>-ifeq ($(RTE_LIBNAME),)
>> >>>>-RTE_LIBNAME := intel_dpdk
>> >>>>endif
>> >>>>
>> >>>># RTE_TARGET is deducted from config when we are building the SDK.
>> >>>>--
>> >>>>1.9.3
>> >>Hi Mark,
>> >>
>> >>How does this patch break compatibility with OVS?
>> >>
>> >>Thanks,
>> >>Sergio
>> >Hey Sergio,
>> >
>> >We use the CONFIG_RTE_BUILD_COMBINE_LIBS and CONFIG_RTE_LINBNAME flags to build a single static DPDK library, named 'libintel_dpdk.a', which OVS links against. Removing the combined library option breaks compatibility with any application that links against the combined DPDK library.
>> >
>> >Is there a strong technical motivation for removing these options?
>> >
>> >Thanks,
>> >Mark
>> From a shared library point of view, it just does not make sense to have
>> applications linked against a 'combined' library that may have different
>> features built in it.
>>
>> Removing these options, aside from the obvious 'less build config option',
>> it simplifies maintenance of makefiles as we currently have a separated
>> makefile with specific rules just for combined library.
>>
>> It is pretty straight forward to build a single combined archive out of
>> multiple archives, would it be acceptable to have a script to do this?
>>
>> Thanks,
>> Sergio
>>
> +1
>
> For the static case, its easy to do a post build combination of archives.  For
> the shared library case, its equally easy to simply create a linker scripts call
> <CONFIG_RTE_LIBNAME>.so that pulls in all the individual libraries.
>
> Neil
>