Help needed building gcc on Arm

[Tim Janes]

On 24/06/2019 11:52, Jonathan Wakely wrote:
> On Sun, 23 Jun 2019 at 19:44, Tim Janes <twjanes@gmail.com> wrote:
>> I am attempting to build gcc 9.1.0 on an Arm7 (Raspberry Pi) running
>> piCore Linux distribution, but i wish it to be build to also run on Arm6
>> (older Pi).
>>
>> My build script looks like this
>>
>> export CFLAGS="-O2 -pipe -march=armv6zk -mtune=arm1176jzf-s
>> -mcpu=arm1176jzf-s -mfpu=vfp -mfloat-abi=hard-fuse-ld=gold"
>> export CXXFLAGS="-O2 -pipe -fno-exceptions -march=armv6zk
>> -mtune=arm1176jzf-s -mcpu=arm1176jzf-s -mfpu=vfp -mfloat-abi=hard
>> -fuse-ld=gold"
>> export LDFLAGS="-L/usr/local/lib"
>>
>>    ../gcc-9.1.0/configure \
>>       --libdir=/usr/lib \
>>       --enable-shared \
>>       --enable-threads=posix \
>>       --enable-__cxa_atexit \
>>       --enable-c99 \
>>       --enable-long-long \
>>       --enable-clocale=gnu \
>>       --enable-languages=c,c++ \
>>       --disable-multilib \
>>       --disable-libstdcxx-pch \
>>       --enable-cloog-backend=isl \
>>       --with-isl=/usr \
>>       --with-system-zlib \
>>       --enable-frame-pointer \
>>       --disable-bootstrap \
>>       --enable-lto \
>>       --with-pkgversion=piCore \
>>       --with-arch=armv6zk \
>>       --with-tune=arm1176jzf-s \
>>       --with-fpu=vfp \
>>       --with-float=hard \
>>       --with-gxx-include-dir=/usr/include/c++/9.1.0
>>
>> but this fails with
>>
>> libtool: compile:
>> /mnt/sda1/piCore/10.x/armv7/tcz/src/gcc/build/./gcc/xgcc
>> -B/mnt/sda1/piCore/10.x/armv7/tcz/src/gcc/build/./gcc/
>> -B/usr/local/armv7l-unknown-linux-gnueabihf/bin/
>> -B/usr/local/armv7l-unknown-linux-gnueabihf/lib/ -isystem
>> /usr/local/armv7l-unknown-linux-gnueabihf/include -isystem
>> /usr/local/armv7l-unknown-linux-gnueabihf/sys-include -DHAVE_CONFIG_H
>> -I../../../gcc-9.1.0/libatomic/config/arm
>> -I../../../gcc-9.1.0/libatomic/config/linux/arm
>> -I../../../gcc-9.1.0/libatomic/config/posix
>> -I../../../gcc-9.1.0/libatomic -I. -Wall -Werror -pthread -g -O2 -pipe
>> -march=armv6zk -mtune=arm1176jzf-s -mcpu=arm1176jzf-s -mfpu=vfp
>> -mfloat-abi=hard -fuse-ld=gold -MT load_1_1_.lo -MD -MP -MF
>> .deps/load_1_1_.lo.Ppo -DN=1 -DIFUNC_ALT=1 -march=armv7-a+fp -c
>> ../../../gcc-9.1.0/libatomic/config/linux/arm/load_n.c  -fPIC -DPIC -o
>> .libs/load_1_1_.o
>> cc1: error: switch '-mcpu=arm1176jzf-s' conflicts with '-march=armv7-a'
>> switch [-Werror]
>> cc1: all warnings being treated as errors
>> make[4]: *** [Makefile:854: load_1_1_.lo] Error 1
>>
>> How do I stop it picking up march=armv7-a - presumably it is getting
>> that from the machine I am running on.?
>>
>> I have tried adding --with-cpu=arm1176jzf-s to the configuration, with
>> this I had to remove with-arch and with-tune, but the build gives
>> exactly the same error.
>>
>> Any help or suggestuions would be welcome.
> GCC assumes you want to build a compiler that runs on the system it's
> being built. To run on a different system you need to build a
> cross-compiler, so I think you should use something like:
>
> --host=armv6zk-unknown-linux-gnueabihf
>
> in the configure arguments.
Thanks I will try that and let you know if that fixes it.

I am however even more confused, last night I dug out an old arm6 
system, and stared afresh, after 18hours running it has failed with the 
same error, we are running on an arm6 so how is it picking up arm7-a?

cc1: error: switch '-mcpu=arm1176jzf-s' conflicts with '-march=armv7-a'

Tim.