From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thomas Petazzoni Date: Sun, 18 Oct 2015 22:02:01 +0200 Subject: [Buildroot] [PATCH 1/1] package/libdcadec: Add -fPIC to static build, enable shared build In-Reply-To: References: <1445184515-6049-1-git-send-email-bernd.kuhls@t-online.de> <20151018210520.0c6971da@free-electrons.com> Message-ID: <20151018220201.077078ae@free-electrons.com> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: buildroot@busybox.net Hello, On Sun, 18 Oct 2015 21:52:38 +0200, Samuel Martin wrote: > > None of these configurations have BR2_STATIC_LIBS=y, so I fail to see > > why adding -fPIC when BR2_STATIC_LIBS=y would fix those issues. > > > > Moreover, using -fPIC for statically linked configurations generally > > doesn't make sense: the point of PIC code is to be Position > > Independent, which is needed for shared libraries. But not for > > statically linked programs. > > AFAI understand these build failures, the problem comes from the > static library libdcadec.a that is unconditionnally built. > When the config has BR2_SHARED_LIBS=y, this static library got built > without -fPIC, then is used by ffmpeg to be linked against for some > shared objects libraries (e.g. libavcodec.so). That's right here that > error occurs. This, I'm OK with. > >> The upstream Makefile also allows building a shared library if > >> CONFIG_SHARED=1 is added to _BUILD_CMDS. > > > > This probably fixes the problem however. > > To fix this the options are: > 1) build libdcadec as a shared library, if it is supported; > 2) or, add -fPIC when BR2_SHARED_LIBS=y; > 3) or, unconditionally add -fPIC. > > My preference is option 1). Obviously, (1) is the right solution here. > > So, can you explain the addition of -fPIC for BR2_STATIC_LIBS=y > > configurations? > > IIRC, -fPIC on static libs does not have any harmful consequences, > only a slight overhead at some point due to some indirection. Correct. But it doesn't make sense to explicitly add -fPIC when BR2_STATIC_LIBS=y. Thomas -- Thomas Petazzoni, CTO, Free Electrons Embedded Linux, Kernel and Android engineering http://free-electrons.com