From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: <dev-bounces@dpdk.org> Received: from dpdk.org (dpdk.org [92.243.14.124]) by inbox.dpdk.org (Postfix) with ESMTP id 123FDA0350; Wed, 1 Jul 2020 17:45:20 +0200 (CEST) Received: from [92.243.14.124] (localhost [127.0.0.1]) by dpdk.org (Postfix) with ESMTP id 7E7721D172; Wed, 1 Jul 2020 17:45:19 +0200 (CEST) Received: from mga05.intel.com (mga05.intel.com [192.55.52.43]) by dpdk.org (Postfix) with ESMTP id A72F61D161 for <dev@dpdk.org>; Wed, 1 Jul 2020 17:45:18 +0200 (CEST) IronPort-SDR: SMXA58madM2wGYpfsujkVdbJ83bNYlhm5M22SNOvkA9MP0cYiPXKmDgrGCWalDClpyM/P+0e+f piGhIVLPYklg== X-IronPort-AV: E=McAfee;i="6000,8403,9669"; a="231477838" X-IronPort-AV: E=Sophos;i="5.75,300,1589266800"; d="scan'208";a="231477838" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga005.jf.intel.com ([10.7.209.41]) by fmsmga105.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 01 Jul 2020 08:45:17 -0700 IronPort-SDR: aK5qFc51KwGlG7KNheCCof16bjeGRMmGw79U8VAo5hAl0Y8NKX96bd1oxabkVpIghW1p0xRv3p T6coUI1KGa/w== X-IronPort-AV: E=Sophos;i="5.75,300,1589266800"; d="scan'208";a="455146896" Received: from bricha3-mobl.ger.corp.intel.com ([10.251.80.77]) by orsmga005-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-SHA; 01 Jul 2020 08:45:15 -0700 Date: Wed, 1 Jul 2020 16:45:12 +0100 From: Bruce Richardson <bruce.richardson@intel.com> To: Thomas Monjalon <thomas@monjalon.net> Cc: dev@dpdk.org, david.marchand@redhat.com, ktraynor@redhat.com, bluca@debian.org, sunil.pai.g@intel.com Message-ID: <20200701154512.GH595@bricha3-MOBL.ger.corp.intel.com> References: <20200429100831.398-1-bruce.richardson@intel.com> <7587667.Wdl7rU7Jnr@thomas> <20200701151651.GG595@bricha3-MOBL.ger.corp.intel.com> <5534902.P14CUFCJsY@thomas> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5534902.P14CUFCJsY@thomas> Subject: Re: [dpdk-dev] [PATCH v3 5/7] build/pkg-config: output driver libs first for static build X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: DPDK patches and discussions <dev.dpdk.org> List-Unsubscribe: <https://mails.dpdk.org/options/dev>, <mailto:dev-request@dpdk.org?subject=unsubscribe> List-Archive: <http://mails.dpdk.org/archives/dev/> List-Post: <mailto:dev@dpdk.org> List-Help: <mailto:dev-request@dpdk.org?subject=help> List-Subscribe: <https://mails.dpdk.org/listinfo/dev>, <mailto:dev-request@dpdk.org?subject=subscribe> Errors-To: dev-bounces@dpdk.org Sender: "dev" <dev-bounces@dpdk.org> On Wed, Jul 01, 2020 at 05:36:07PM +0200, Thomas Monjalon wrote: > 01/07/2020 17:16, Bruce Richardson: > > On Wed, Jul 01, 2020 at 04:42:33PM +0200, Thomas Monjalon wrote: > > > 30/06/2020 16:14, Bruce Richardson: > > > > When calling pkg-config --static --libs, pkg-config will always output the > > > > regular libs first, and then the extra libs from libraries.private field, > > > > > > s/libraries.private/Libs.private/ > > > > > > > since the assumption is that those are additional dependencies for building > > > > statically that the .a files depend upon. > > > > > > > > However, for DPDK, we only link the driver files for static builds, and > > > > those need to come *before* the regular libraries. To get this result, we > > > > need two pkgconfig files for DPDK, one for the shared libs, and a second > > > > for the static libs and drivers, which depends upon the first. Using a > > > > dependency means that the shared libs are printed only after the > > > > libraries.private field rather than before. > > > > > > s/libraries.private/Libs.private/ > > > > > > > Without this patch, the linking works in DPDK because in all cases we > > > > specify the libraries after the drivers in the Libs.private line, ensuring > > > > that the references to the libs from the drivers can be resolved. The > > > > current output is therefore of the form, "(shared)libs, drivers, > > > > (static)libs", while after this patch the output is, "drivers, > > > > (static)libs, (shared)libs". The former case will not work if we use the > > > > --whole-archive flag on the static libs as it will lead to duplicate > > > > definitions due to some references having been previously resolved from the > > > > shared libraries. By ensuring the shared libraries come last in the link > > > > link, this issue does not occur, as duplicate references when linking the > > > > shared libs will be ignored. > > > > > > > > Signed-off-by: Bruce Richardson <bruce.richardson@intel.com> > > > > Acked-by: Luca Boccassi <bluca@debian.org> > > > > Acked-by: Sunil Pai G <sunil.pai.g@intel.com> > > > > --- > > > > +# When calling pkg-config --static --libs, pkg-config will always output the > > > > +# regular libs first, and then the extra libs from libraries.private field, > > > > +# since the assumption is that those are additional dependencies for building > > > > +# statically that the .a files depend upon. However, for DPDK, we only link > > > > +# the driver files for static builds, and those need to come *before* the > > > > +# regular libraries. To get this result, we need two pkgconfig files for DPDK, > > > > +# one for the shared libs, and a second for the static libs and drivers, which > > > > +# depends upon the first. Using a dependency means that the shared libs are > > > > +# printed only after the libraries.private field rather than before. > > > > > > This is not obvious. In order to avoid messing it up in future, > > > I suggest this longer reword: > > > > > > # When calling pkg-config --static --libs, pkg-config will always output the > > > # regular libs first, and then the extra libs from Libs.private field, > > > # since the assumption is that those are additional dependencies for building > > > # statically that the .a files depend upon. The output order of .pc fields is: > > > # Cflags Libs Libs.private Requires Requires.private > > > # The fields Requires* are for package names. > > > # The flags of the DPDK libraries must be defined in Libs* fields. > > > # However, the DPDK drivers are linked only in static builds (Libs.private), > > > # and those need to come *before* the regular libraries (Libs field). > > > # This requirement is satisfied by moving the regular libs in a separate file > > > # included in the field Requires (after Libs.private). > > > # Another requirement is to allow linking dependencies as shared libraries, > > > # while linking static DPDK libraries and drivers. It is satisfied by > > > # listing the static files in Libs.private with the explicit syntax -l:libfoo.a. > > > # As a consequence, the regular DPDK libraries are already listed as static > > > # in the field Libs.private. The second occurences of DPDK libraries, > > > # included from Requires and used for shared library linkage case, > > > # are skipped in the case of static linkage thanks to the flag --as-needed. > > > > > > # Link order summary: > > > # libdpdk.Libs.private: whole-archive(static drivers/libs), drivers deps flags > > > # libdpdk.Requires: libdpdk-libs package > > > # libdpdk-libs.Libs: as-needed(shared libs) > > > # libdpdk-libs.Libs.private: libs deps flags > > > # libdpdk.pc.Requires.private: deps packages > > > > > > > > > If you agree, I could change this comment while merging. > > > I would add my Signed-off ;) > > > > > > > This seems generally ok, but probably should just be added as part of patch > > #7 when all parts of the above have been applied. > > > > Couple of comments: > > * One small nit is that cflags are not output as part of the --libs call, so > > you can remove them from the list on line 5 of the comment. They aren't > > really relevant to this comment/essay. > > Yes, I will remove Cflags. > > > * I find the link-order summary to actually be more confusing than helpful. > > I think the text block is explanatory enough. It just confuses things > > introducing the extra details of what goes in the requires-private or > > libs-private of the libdpdk.pc file. That's just regular stuff, unrelated > > to the changes or to DPDK special-case of needing private libs first. > > The intent of this summary was to help navigating > for future changes in this area. > Personnaly it helps me, but it is maybe more a developer note > that can be deduced from the rest. > I can remove it. > Ok thanks. If you are happy to make these comment changes on apply, please feel free to do so, thanks. [BTW: I think the shebang line on the new python script needs a "python" changed to "python3" also. I missed that in the latest revision, sorry!]