armv7, building p7zip and -fPIC

[Ian Lepore]

On Sat, 2017-10-07 at 21:59 +0300, Guy Yur wrote:
> On 7 October 2017 at 21:40, Warner Losh <imp at bsdimp.com> wrote:
> > 
> > 
> > 
> > On Sat, Oct 7, 2017 at 11:24 AM, Guy Yur <guyyur at gmail.com> wrote:
> > > 
> > > 
> > > Hi,
> > > 
> > > Does armv7 need -fPIC when compiling?
> > > 
> > > Building archivers/p7zip fails with:
> > > /usr/bin/ld: 7zEncode.o(.text+0x2d04): unresolvable R_ARM_MOVW_ABS_NC
> > > relocation against symbol `_ZTIi@@CXXABI_1.3'
> > > /usr/bin/ld: final link failed: Nonrepresentable section on output
> > > c++: error: linker command failed with exit code 1 (use -v to see
> > > invocation)
> > > *** [../../../../bin/7z.so] Error code 1
> > > 
> > > make[3]: stopped in
> > > 
> > > /usr/wrkdir/usr/ports/archivers/p7zip/work/p7zip_16.02/CPP/7zip/Bundles/Format7zFree
> > > 1 error
> > > 
> > > If I add "CFLAGS_armv7= -fPIC" in the port Makefile it builds fine.
> > > The port has -fPIC for aarch64, amd64, powerpc and sparc64.
> > > 
> > > Is it a difference from armv6?
> > > When I previously built for armv6 it worked without the option.
> > 
> > armv7 is new in FreeBSD (two days old), and maybe you are tripping over
> > something inside the port that optimized for it? Is there a
> > CFLAGS+armv6=-fPIC? I don't see it with a quick grep, but you never know...
> > If that's what it takes to fix it, maybe you should submit that to the port
> > maintainer?
> > 
> > Warner
> Hi,
> 
> Seems to indeed be a difference between armv6 and armv7,
> found this: https://bugs.launchpad.net/ubuntu/+source/gcc-4.4/+bug/503448
> 
> I will submit a patch to the port maintainer to add CFLAGS for armv7.
> 
> Thanks,
> Guy

This is really not just an armv7-only thing, the -fPIC flag should
always be used.  On armv6 (and some other non-arm arches) it will
accidentally work without that flag, but that doesn't make it right.

--- Ian