Re: Bug when cross-compiling for ppc

[Simon Marchi <simon.marchi@polymtl.ca>]

On 9/13/23 22:25, Simon Marchi via Gdb wrote:
> On 9/12/23 12:42, Vincent Fortier via Gdb wrote:
>> As introduction, I part of SynoCommunity who maintains free software
>> packages that can be installed on synology NAS.  Multiple archs are
>> supported from armv5, v7, v8, ppc, i686 and x64.  I am able to build
>> gdb for all archs with exception of ppc, more specifically qoriq arch
>> using gcc-4.9.3 from Synology provided toolchain.
>>
>> github PR available here: https://github.com/SynoCommunity/spksrc/pull/5879
>>
>> I was finally able to figure out why (now needs to know how to fix it)
>> gdb fails to cross-compile for ppc.  I am able to reproduce this
>> problem on both gdb-7.12.1 and latest 13.2.
>>
>> Basically, when it goes into the configure script under sim/ppc at a
>> certain point it tests the "build" c compiler:
>>
>> checking for i686-pc-linux-gcc... gcc
>> checking whether the C compiler works... no
>> configure: error: in
>> `/home/spksrc/qoriq-debug/spksrc/cross/gdb-latest/work-qoriq-6.2.4/gdb-13.2/sim/ppc/build.4119280':
>> configure: error: C compiler cannot create executables
>> See `config.log' for more details
>> mv: cannot stat 'config.h': No such file or directory
>>
>> The end-result way later on is that build-config.h is then missing:
>>
>> fatal error: build-config.h: No such file or directory
>>    23 | #include "build-config.h"
>>       |          ^~~~~~~~~~~~~~~~
>> compilation terminated.
>>
>> As at the end of sim/ppc/configure it does a mv config.h
>> ../build-config.h but config.h was not generated in the first place.
>>
>> What I ended-up doing is commenting out the tmpdir removal from that
>> configure script:
>>
>>   CFLAGS="${saved_CFLAGS}"
>>   mv config.h ../build-config.h
>>   cd ..
>>   ###rm -rf $tempdir
>>
>> Which allowed me to keep track of the real error happening in background:
>>
>> configure:2482: checking whether the C compiler works
>> configure:2504: gcc -g -O
>> -I/home/spksrc/qoriq-debug/spksrc/toolchain/syno-qoriq-6.2.4/work/powerpc-e500v2-linux-gnuspe/powerpc-e500v2-linux-gnuspe/sysroot/usr/include
>> -mcpu=8548 -mhard-float -mfloat-gprs=double
>> -I/home/spksrc/qoriq-debug/spksrc/cross/gdb-latest/work-qoriq-6.2.4/install/usr/local/gdb/include
>>   conftest.c  >&5
>> gcc: warning: '-mcpu=' is deprecated; use '-mtune=' or '-march=' instead
>> gcc: error: unrecognized command-line option '-mfloat-gprs=double'
>> configure:2508: $? = 1
>> configure:2546: result: no
>>
>> When testing the "build" compiler it includes the "target" flags which
>> includes -mcpu=8548 -mhard-float -mfloat-gprs=double. In turns these
>> flags should never get used on with "build" compiler making it to
>> fail.
>>
>> Now the question is, how to fix that?  Help would be much welcomed :)
> 
> Not a way to fix it but to circumvent it.  Do you need sim support (it's
> a simulator hosted inside GDB)?  If not, you can configure with
> --disable-sim, it will skip configuring/building the sim directory.

Also, what does you full configure line looks like?

Simon