From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thomas Petazzoni Date: Sun, 22 Apr 2018 10:28:28 +0200 Subject: [Buildroot] [PATCH v2] lz4: improve static only build support In-Reply-To: <20180421210510.v4zwz6y57z7stryx@tarshish> References: <20180420084143.3b20bd3a@windsurf.numericable.fr> <20180421210510.v4zwz6y57z7stryx@tarshish> Message-ID: <20180422102828.01dd1455@windsurf> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: buildroot@busybox.net Hello Baruch, On Sun, 22 Apr 2018 00:05:10 +0300, Baruch Siach wrote: > > Admittedly, it isn't a huge improvement, but for consistency it would > > be good to do that. > > Many other packages build both shared and static libraries when > BR2_SHARED_LIBS=y. Yes, I know. I don't know how strict we want to be about this. Probably not too much because it doesn't matter that much. > This particular case is easy enough to fix, though. Yes, that's the point: for this package, it's super easy to fix, so it's nice to do it. > Is there any advantage to not building the static library when > BR2_SHARED_LIBS=y other than the small build time reduction? In some cases there is more than a "small build time reduction". The object files that go in a shared library must be built with -fPIC. Such object files can also be used in a static library, but the code is not as optimized as it could be, and therefore object files that go in a static library should ideally not be built with -fPIC. I believe some packages (but not many) do build their object files twice, once with -fPIC for the shared library, once without -fPIC for the static library. This creates more than a "small build time reduction". >From the commit log of commit f1d3e09895b245da9d54bbaef36e5de95269034e: For example, a static+shared build of libglib2 takes 1 minutes and 59 seconds, with a final build directory of 96 MB. A shared-only build of libglib2 takes only 1 minutes and 31 seconds (almost a 25% reduction of the build time), and the final build directory weights 89 MB (a reduction of almost 8%). Best regards, Thomas -- Thomas Petazzoni, CTO, Bootlin (formerly Free Electrons) Embedded Linux and Kernel engineering https://bootlin.com