[Buildroot] Switching to a two stage gcc build

[Thomas Petazzoni <thomas.petazzoni@free-electrons.com>]

Alexey, Anton,

I'm currently working on switching from a three stage gcc build to a
two stage gcc build in Buildroot. Currently, what we do is:

 * host-gcc-initial
 * linux-headers
 * first build of C library, just to install the headers and start files
 * host-gcc-intermediate
 * complete build of C library
 * host-gcc-final

I'm switching to the simpler (and faster) solution which allows to
remove host-gcc-intermediate:

 * host-gcc-initial
 * linux-headers
 * complete build of C library
 * host-gcc-final

The attached patch works fine for ARM, but it doesn't work for ARC. The
problem is that with the two stage gcc build, we build libgcc in
host-gcc-initial instead of host-gcc-intermediate. This means that
libgcc is now built *before* the C library has installed its headers.
Unfortunately, the ARC version of libgcc uses some headers from the C
library, and therefore fails to build:

/home/test/outputs/arc-uclibc/build/host-gcc-initial-arc-2014.08/build/./gcc/xgcc -B/home/test/outputs/arc-uclibc/build/host-gcc-initial-arc-2014.08/build/./gcc/ -B/home/test/outputs/arc-uclibc/host/usr/arc-buildroot-linux-uclibc/bin/ -B/home/test/outputs/arc-uclibc/host/usr/arc-buildroot-linux-uclibc/lib/ -isystem /home/test/outputs/arc-uclibc/host/usr/arc-buildroot-linux-uclibc/include -isystem /home/test/outputs/arc-uclibc/host/usr/arc-buildroot-linux-uclibc/sys-include    -g -Os -O2  -g -Os -DIN_GCC -DCROSS_DIRECTORY_STRUCTURE  -W -Wall -Wwrite-strings -Wcast-qual -Wstrict-prototypes -Wmissing-prototypes -Wold-style-definition  -isystem ./include   -fPIC -g -DIN_LIBGCC2 -fbuilding-libgcc -fno-stack-protector -Dinhibit_libc  -fPIC -I. -I. -I../.././gcc -I../../../libgcc -I../../../libgcc/. -I../../../libgcc/../gcc -I../../../libgcc/../include    -o gmon.o -MT gmon.o -MD -MP -MF gmon.dep -isystem ../../../libgcc/config/arc/gmon -mno-sdata -c ../../../libgcc/config/arc/gmon/
 gmon.c \
        -fno-strict-aliasing \
        -Wno-extra # suppress inane warning about missing initializer.
In file included from ../../../libgcc/config/arc/gmon/mcount.c:40:0:
../../../libgcc/config/arc/gmon/sys/gmon.h:40:23: fatal error: sys/types.h: No such file or directory
 #include <sys/types.h>
                       ^
compilation terminated.
make[3]: *** [mcount.o] Error 1
make[3]: *** Waiting for unfinished jobs....
grep -v 'include.*fp-bit.h' ../../../libgcc/fp-bit.c >> dp-bit.c
In file included from ../../../libgcc/config/arc/gmon/gmon.c:34:0:
../../../libgcc/config/arc/gmon/sys/gmon.h:40:23: fatal error: sys/types.h: No such file or directory
 #include <sys/types.h>
                       ^
compilation terminated.
make[3]: *** [gmon.o] Error 1
make[2]: *** [all-target-libgcc] Error 2
make[1]: *** [/home/test/outputs/arc-uclibc/build/host-gcc-initial-arc-2014.08/.stamp_built] Error 2

You can reproduce this by applying the attached patch, and using the
following defconfig:

BR2_arcle=y
BR2_ENABLE_SSP=y
BR2_TOOLCHAIN_BUILDROOT_LARGEFILE=y
BR2_TOOLCHAIN_BUILDROOT_INET_IPV6=y
BR2_TOOLCHAIN_BUILDROOT_INET_RPC=y
BR2_TOOLCHAIN_BUILDROOT_WCHAR=y
BR2_TOOLCHAIN_BUILDROOT_USE_SSP=y
BR2_TOOLCHAIN_BUILDROOT_CXX=y

It is also worth mentioning that in the latest master (i.e without my
patch), the ARC toolchain builds fine, but it fails to build Busybox:

{standard input}: Assembler messages:
{standard input}:453: Error: operand out of range (128 is not between -128 and 127)
  CC      libbb/xregcomp.o
make[3]: *** [libbb/xfuncs.o] Error 1
make[3]: *** Waiting for unfinished jobs....

Could you help me solve those issues?

Thanks a lot!

Thomas
-- 
Thomas Petazzoni, CTO, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com
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