Re: [dpdk-dev] Impossible to build external application if user build DPDK with "make config"

[Thomas Monjalon <thomas@monjalon.net>]

27/03/2020 16:53, Tom Barbette:
> Le 27/03/2020 à 16:06, Thomas Monjalon a écrit :
> > 27/03/2020 15:24, Tom Barbette:
> >> Le 27/03/2020 à 14:55, Thomas Monjalon a écrit :
> >>> 27/03/2020 13:35, Tom Barbette:
> >>>> Le 27/03/2020 à 11:35, Thomas Monjalon a écrit :
> >>>>> 27/03/2020 10:14, Tom Barbette:
> >>>>>> CC'ing original participants as I don't see a way out of this.
> >>>>>>
> >>>>>> Le 12/03/2020 à 13:04, Tom Barbette a écrit :
> >>>>>>> Hi all,
> >>>>>>>
> >>>>>>> If the user follows the quick guide
> >>>>>>> (http://core.dpdk.org/doc/quick-start/) DPDK will be compiled in the
> >>>>>>> "build" folder.
> >>>>>>>
> >>>>>>> However, external applications will always fail to build because
> >>>>>>> RTE_SDK_BIN is strictly defined as $RTE_SDK/$RTE_TARGET, and
> >>>>>>> mk/internal/rte.extvars.mk needs to find .config in $RTE_SDK_BIN.
> >>>>>>>
> >>>>>>> Therefore please apply the patch at:
> >>>>>>> http://patchwork.dpdk.org/patch/9991/ that allows external apps to
> >>>>>>> override $RTE_SDK_BIN.
> >>>>>>>
> >>>>>>> Or (less preferable) modify the quick start guide to use something more
> >>>>>>> standard that allows to build with external apps (eg use the menu or
> >>>>>>> propose "make config T=x86_64-native-linuxapp-gcc
> >>>>>>> O=x86_64-native-linuxapp-gcc" instead). It's much easier for external
> >>>>>>> apps maintainer to refer to the DPDK tutorial for DPDK installation.
> >>>>>
> >>>>> I don't understand the issue.
> >>>>> First of all, the external application should link an installed DPDK.
> >>>>> Then you should be able to set $RTE_SDK and $RTE_TARGET to fit
> >>>>> the installation directories.
> >>>>>
> >>>>> Just checked doc/guides/linux_gsg/build_dpdk.rst
> >>>>> I see the whole build process with make is not correctly documented.
> >>>>> It should be:
> >>>>>
> >>>>> 1/
> >>>>> 	make defconfig
> >>>>> 	or
> >>>>> 	make config T=x86_64-native-linux-gcc O=mybuild
> >>>>>
> >>>>> 2/	make -j4 O=mybuild
> >>>>>
> >>>>> 3/	make install O=mybuild DESTDIR=myinstall prefix=
> >>>>>
> >>>>> 4/	RTE_SDK=$(pwd)/myinstall/share/dpdk RTE_TARGET=x86_64-native-linux-gcc make -C myapp
> >>>>>
> >>>>> Please can you confirm it works?
> >>>>>
> >>>>>
> >>>>
> >>>> I don't think it is usual to link against an "installed" DPDK, actually.
> >>>> I've only seen people explaining "build DPDK with 1 & 2", which is
> >>>> probably why the quick start also use only that and the usertools menu
> >>>> also only builds in the usual folder SDK/TARGET.
> >>>>
> >>>> Then also using the install method you propose, I'm missing a few
> >>>> libraries, eg -lethdev which I would have to find using
> >>>> -L$RTE_SDK/../../lib which does not sound great. But adding a link to
> >>>> ../../lib under share fixes the problem, and the install script could do it.
> >>>
> >>> Why are you trying to link a library in RTE_SDK?
> >>> You should set the installed library directory with LD_LIBRARY_PATH.
> >>
> >> I don't want DPDK to be installed system-wide. I have a lot of versions,
> >> modified for different projects from different people, that has
> >> different compatibility level. And even, different versions compiled for
> >> different CPU architectures among our cluster.
> >>
> >> I prefer to only rely $RTE_SDK to know where "everything is". I could
> >> tell to my users to add something in their LD_LIBRARY_PATH, but I would
> >> prefer to stick to only the standard RTE_SDK and RTE_TARGET.
> > 
> > You can install inside RTE_SDK.
> > This is what the command I gave you to test do.
> > Installation is just organizing files in a directory so it can be consumed.
> > Did you read the commands I sent? It is installing in $(pwd)/myinstall.
> 
> Yes yes and I tried it as I said, leading to this lib problem. Still 
> needs to ask the user to modify LD_LIBRARY_PATH to basically point it to 
> $RTE_SDK/../../lib. I would have wanted to avoid that third one, but okay.

I understand.
LD_LIBRARY_PATH requirement is standard when linking with a library
which is not in a standard directory.

> > After install, RTE_SDK becomes $(pwd)/myinstall/share/dpdk.
> > 
> >>>> Making RTE_SDK_BIN a ?= instead of a := would allow us to fix the
> >>>> non-installed, but built-in-a-funny-folder installation path easily.
> >>>>
> >>>> So I would recommend doing the lib link, but still the change proposed
> >>>> because I'm really not sure people "install" DPDK...
> >>>
> >>> The correct method is installing the library and using standard environment variables.
> >>> The only change I am OK to do is improving the documentation.
> >>
> >> You know best... I still think make install is unnecessary in most cases
> >> so I would not change the doc either...
> > 
> > I say "make install" is a must and there is no reason no to do it.
> Ok. Maybe add it to the quick steps then? Also the menu does not install 
> "with T defined and DESTDIR undefined" and I always used that, which may 
> have led me to believe make install was not really part of the process.

"make install T=" is an old method for compiling.
The real install process does not involve T=.
I will try to make all these steps more clear.

> > Please check the steps I wrote for you.