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[2a01:cb0c:5:a600:3456:36f7:e65e:d1a0]) by smtp.gmail.com with ESMTPSA id e27sm11309150wrc.9.2020.11.26.08.32.27 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 26 Nov 2020 08:32:27 -0800 (PST) Date: Thu, 26 Nov 2020 17:32:26 +0100 From: Olivier Matz To: Bruce Richardson Cc: dev@dpdk.org, Harry van Haaren , Keith Wiles , Luca Boccassi , stable@dpdk.org Message-ID: <20201126163226.GZ1898@platinum> References: <20201126142042.24741-1-olivier.matz@6wind.com> <20201126152846.GD1340@bricha3-MOBL.ger.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201126152846.GD1340@bricha3-MOBL.ger.corp.intel.com> User-Agent: Mutt/1.10.1 (2018-07-13) Subject: Re: [dpdk-dev] [PATCH] app: fix plugin load on static builds X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" Hi Bruce, Thanks for the feedback. On Thu, Nov 26, 2020 at 03:28:46PM +0000, Bruce Richardson wrote: > On Thu, Nov 26, 2020 at 03:20:42PM +0100, Olivier Matz wrote: > > When dpdk is compiled as static libraries, it is not possible > > to load a plugin from an application. We get the following error: > > > > EAL: librte_pmd_xxxx.so: undefined symbol: per_lcore__rte_errno > > > > This happens because the dpdk symbols are not exported. Add them to the > > dynamic symbol table by using '-Wl,--export-dynamic'. This option was > > previously present when compiled with Makefiles, it was introduced in > > commit f9a08f650211 ("eal: add support for shared object drivers") > > > > Fixes: 16ade738fd0d ("app/testpmd: build with meson") > > Fixes: 89f0711f9ddf ("examples: build some samples with meson") > > Cc: stable@dpdk.org > > > > Signed-off-by: Olivier Matz > > --- > > > > Hi, > > > > Maybe the patch can be improved: I suppose that --export-dynamic > > should only be added in case we are linking in static mode. Any > > help about how to do that is welcome. > > get_option('default_library') == 'static' > > However, if the flag is harmless in shared linking mode, I don't think we > need bother with this. ok > > > > There is probably a better place to define the default ldflags for > > all applications (to factorize between app and example). > > > > Also, should this flag be advertised in pkg-config? > > > Perhaps. However, I'm not sure how common it would be for people to static > link their own apps with DPDK and then want to plug in extra drivers after > the fact? Are there any possible negative impacts to making that change? I don't know if it is common, but this is something we do :) > If we weren't right before the release deadline I'd definitely suggest > adding it to the pkg-config files. At this late stage in release, I'm more > cautious. Yes, it is too late for 20.11. Maybe even for this patch without updating pkg-config. > > > Thanks, > > Olivier > > > > > > app/meson.build | 3 +++ > > examples/meson.build | 4 +++- > > 2 files changed, 6 insertions(+), 1 deletion(-) > > > > diff --git a/app/meson.build b/app/meson.build > > index eb74f215a3..92479c7729 100644 > > --- a/app/meson.build > > +++ b/app/meson.build > > @@ -25,6 +25,7 @@ apps = [ > > lib_execinfo = cc.find_library('execinfo', required: false) > > > > default_cflags = machine_args + ['-DALLOW_EXPERIMENTAL_API'] > > +default_ldflags = ['-Wl,--export-dynamic'] > > > > foreach app:apps > > build = true > > @@ -32,6 +33,7 @@ foreach app:apps > > sources = [] > > includes = [] > > cflags = default_cflags > > + ldflags = default_ldflags > > objs = [] # other object files to link against, used e.g. for > > # instruction-set optimized versions of code > > > > @@ -58,6 +60,7 @@ foreach app:apps > > executable('dpdk-' + name, > > sources, > > c_args: cflags, > > + link_args: ldflags, > > link_whole: link_libs, > > dependencies: dep_objs, > > install_rpath: join_paths(get_option('prefix'), > > diff --git a/examples/meson.build b/examples/meson.build > > index 46ec80919e..def4540e8f 100644 > > --- a/examples/meson.build > > +++ b/examples/meson.build > > @@ -63,6 +63,7 @@ default_cflags = machine_args > > if cc.has_argument('-Wno-format-truncation') > > default_cflags += '-Wno-format-truncation' > > endif > > +default_ldflags = ['-Wl,--export-dynamic'] + dpdk_extra_ldflags > > > > foreach example: examples > > name = example.split('/')[-1] > > @@ -70,6 +71,7 @@ foreach example: examples > > sources = [] > > allow_experimental_apis = false > > cflags = default_cflags > > + ldflags = default_ldflags > > > > ext_deps = [execinfo] > > includes = [include_directories(example)] > > @@ -91,7 +93,7 @@ foreach example: examples > > executable('dpdk-' + name, sources, > > include_directories: includes, > > link_whole: link_whole_libs, > > - link_args: dpdk_extra_ldflags, > > + link_args: ldflags, > > c_args: cflags, > > dependencies: dep_objs) > > elif not allow_skips > > -- > > 2.25.1 > > > > Patch looks reasonable to me. In terms of other approaches, we have: > > 1. Add "add_project_link_arguments('-Wl,--export-dynamic', language: 'c')" > to "config/meson.build". This has the advantage of being a lot shorter, but > it would apply to all .so's too, so not sure if there is any impact there. I will check if there is any impact on .so with this approach. > 2. If there is no reason why any particular app would want to not provide > this flag, you can skip defining a new ldflags variable and just add the > flag into the existing link_args line for each app and example. However, > your approach here, though longer, is more in keeping with the style of > what is already there.