[Buildroot] [PATCH v2,1/1] gnuchess: needs -fPIC

Thomas Petazzoni thomas.petazzoni at bootlin.com
Sun Jan 13 13:13:29 UTC 2019


Hello Fabrice,

On Sat, 12 Jan 2019 18:55:05 +0100, Fabrice Fontaine wrote:
> When building with -O2 (or -O3) on ARM cortex-M cpus, link fails on:
> 
> /home/rclinux/rc-buildroot-test/scripts/instance-0/output/host/bin/arm-linux-g++ -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64  -O2 -Wl,-elf2flt -static  -Wl,-elf2flt -static   -Wl,-elf2flt -static -o gnuchess main.o components.o  frontend/libfrontend.a adapter/libadapter.a engine/libengine.a -lreadline -lncurses
> ERROR: reloc type R_ARM_THM_MOVW_ABS_NC unsupported in this context
> ERROR: reloc type R_ARM_THM_MOVT_ABS unsupported in this context
> ERROR: reloc type R_ARM_THM_MOVW_ABS_NC unsupported in this context
> ERROR: reloc type R_ARM_THM_MOVT_ABS unsupported in this context
> ERROR: reloc type R_ARM_THM_MOVW_ABS_NC unsupported in this context
> ERROR: reloc type R_ARM_THM_MOVT_ABS unsupported in this context
> ERROR: reloc type R_ARM_THM_MOVW_ABS_NC unsupported in this context
> 
> To fix this, pas -fPIC unconditionnally
> 
> Fixes:
>  - http://autobuild.buildroot.org/results/7918757b255ed41609609d2083c2d8904ff3136e
> 
> Signed-off-by: Fabrice Fontaine <fontaine.fabrice at gmail.com>

I'm sorry but this doesn't make sense to me. -fPIC is for Position
Independent Code, which is needed when building shared libraries. Here
we are building with -static on Cortex-M which doesn't even have
support for shared libraries. So building with -fPIC doesn't make sense
I believe. It seems to be more a workaround than a real fix.

Perhaps this should be discussed with upstream binutils, or at least a
proper investigation be done about those relocation types ?

Best regards,

Thomas
-- 
Thomas Petazzoni, CTO, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com



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