Cross compilation

Kai Ruottu
Fri Nov 10 16:15:00 GMT 2017

Kai Ruottu kirjoitti 10.11.2017 klo 11:21:
> RAVI DEWANGAN kirjoitti 10.11.2017 klo 4:56:
>> Hi GNU Team,
>> Could you please guide me regarding cross compilation.
>> I am trying to cross compile the toolchain for FreeBSD11(target) using
>> Ubuntu16.04(host).
>> The issue is
>> /home/rdewangan/freebsd/gcc-7.2.0/build/./gcc/xgcc
>> -B/home/rdewangan/freebsd/gcc-7.2.0/build/./gcc/
>> -B/opt/freebsd_toolchain/x86_64-pc-freebsd11/bin/
>> -B/opt/freebsd_toolchain/x86_64-pc-freebsd11/lib/ -isystem
>> /opt/freebsd_toolchain/x86_64-pc-freebsd11/include -isystem
>> /opt/freebsd_toolchain/x86_64-pc-freebsd11/sys-include    -g -O2 -O2  -g
>> -O2 -DIN_GCC  -DCROSS_DIRECTORY_STRUCTURE  -W -Wall -Wno-narrowing
>> -Wwrite-strings -Wcast-qual -Wstrict-prototypes -Wmissing-prototypes
>> -Wold-style-definition  -isystem ./include   -fpic -pthread -g 
>> -fbuilding-libgcc -fno-stack-protector -Dinhibit_libc  -fpic -pthread 
>> -I.
>> -I. -I../.././gcc -I../../../libgcc -I../../../libgcc/.
>> -I../../../libgcc/../gcc -I../../../libgcc/../include -DHAVE_CC_TLS  -o
>> _muldi3.o -MT _muldi3.o -MD -MP -MF _muldi3.dep -DL_muldi3 -c
>> ../../../libgcc/libgcc2.c -fvisibility=hidden -DHIDE_EXPORTS
>> In file included from ../../../libgcc/../gcc/tsystem.h:44:0,
>>                   from ../../../libgcc/libgcc2.c:27:
>> /home/rdewangan/freebsd/gcc-7.2.0/build/gcc/include/stddef.h:56:10: 
>> fatal
>> error: sys/_types.h: No such file or directory
>>   #include <sys/_types.h>
>>            ^~~~~~~~~~~~~~
>> compilation terminated.
>> Makefile:491: recipe for target '_muldi3.o' failed
> For a "working compiler" one needs also the target C library. Prebuilt 
> and pretested
> in your case when your FreeBSD system is already made.  There isn't 
> much difference
> between a native and a cross compiler in this issue, both require the 
> target C library
> during the GCC build when the extra libraries : libgcc, libstdc++, 
> libssp etc will be built.
> A cross compiler needs also the binutils made for the "host-to-target" 
> use but a native
> build usually already has also them prebuilt, sometimes as non-GNU 
> "native ones".
> Furthermore the target C library must be put into a separate $SYSROOT 
> on the host.
> Not in it's "native" place (usually '/lib*', '/usr/include' and 
> '/usr/lib*' like in Linux) but
> in a sysroot like '/opt/freebsd_toolchain/sysroot' in your case, the 
> native FreeBSD
> sysroot '/' being replaced with this.

Just for a fun I tried a gcc-7.2.0 based crosscompiler for FreeBSD 
11.1/amd64. First built
binutils-2.24.51 for it, then unpacked the 'base.txz' and 'lib32.txz' 
into my chosen sysroot.
Then configured the GCC sources and used 'make'.  A problem was seen in 
the libstdc++
build :

libtool: compile:  /home/src-old/gcc-7.2.0/build/./gcc/xgcc 
-shared-libgcc -B/home/src-old/gcc-7.2.0/build/./gcc -nostdinc++ 
-B/opt/cross/x86_64-freebsd11.1/lib/ -isystem 
/opt/cross/x86_64-freebsd11.1/include -isystem 
-I/home/src-old/gcc-7.2.0/libstdc++-v3/libsupc++ -D_GLIBCXX_SHARED 
-fno-implicit-templates -Wall -Wextra -Wwrite-strings -Wcast-qual -Wabi 
-fdiagnostics-show-location=once -ffunction-sections -fdata-sections 
-frandom-seed=new_opa.lo -g -O2 -std=gnu++1z -c 
../../../../libstdc++-v3/libsupc++/  -fPIC -DPIC 
-D_GLIBCXX_SHARED -o new_opa.o
../../../../libstdc++-v3/libsupc++/ In function 'void* 
aligned_alloc(std::size_t, std::size_t)':
../../../../libstdc++-v3/libsupc++/ error: 'void* 
aligned_alloc(std::size_t, std::size_t)' was declared 'extern' and later 
'static' [-fpermissive]
  aligned_alloc (std::size_t al, std::size_t sz)
In file included from 
                  from ../../../../libstdc++-v3/libsupc++/
/home/src-old/gcc-7.2.0/build/gcc/include-fixed/stdlib.h:178:8: note: 
previous declaration of 'void* aligned_alloc(size_t, size_t)'
  void * aligned_alloc(size_t, size_t) __malloc_like __alloc_align(1)
make[4]: *** [new_opa.lo] Virhe 1
make[4]: Poistutaan hakemistosta 
make[3]: *** [all-recursive] Virhe 1

Seemingly the same problem was with the x86_64-freebsd10.1 target which 
I tried first after updating the
earlier gcc-4.9.2 to gcc-4.9.3 with it. No problems in that build. Will 
check the FreeBSD 11.1 with gcc-4.9.3
Probably this problem with gcc-7.2.0 is easy to fix but now Ravi knows 
what to expect :)

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