Re: [gentoo-embedded] toolchain.eclass and cross-compiling gcc [SOLVED]

[Christopher Friedt]

Hi, sorry it took me so long to reply!

I was doing something that I probably should have realized was a bad 
idea right from the start.

While cross-compiling gcc (build=i686,host=arm,target=arm) I had CFLAGS 
and CXXFLAGS set - Doh!!

It has nothing(?) to do with --enable-serial (which I guess I 
interpreted incorrectly anyway)

Cross-compiling gcc kept failing at libiberty saying "cannot compute 
suffix of object files". And I was seeing that libiberty was being 
configured for build=i686 _and_ host=i686.

What I didn't realize at first was that libiberty is configured twice 
when cross-compiling gcc. The first time for the host machine and the 
second time for the build machine. The host libiberty files are located 
in gcc-build/libiberty. The build libiberty files are located in 
gcc-build/build-i686-pc-linux-gnu/libiberty.

I assumed at first it was only necessary to configure libiberty once - 
even when cross compiling gcc. When I saw it configured for the second 
time, with build=i686 and host=i686, i thought "hey a secondary stage of 
the configure process isn't realizing that i said 
host=arm-softfloat-inux-gnu the fist time!"

That's why i assumed --enable-serial-host,build,target would fix my problem.

Just so other people hopefully find this on Google and don't waste as 
much of their time as i did, I'm going to append all of my values below.

INCORRECT:

=======================================================================
$ CXXFLAGS="-O2 -mcpu=arm920t" CFLAGS="-O2 -mcpu=arm920t" 
../gcc-4.1.2/configure ${MY_ECONF_OPTS} --build=i686-pc-linux-gnu 
--target=arm-softfloat-linux-gnu --host=arm-softfloat-linux-gnu 
--disable-checking --disable-werror --enable-secureplt 
--disable-libunwind-exceptions --disable-nls --with-float=soft 
--with-cpu=arm920t 
--with-gxx-include-dir=/usr/lib/gcc/arm-softfloat-linux-gnu/4.1.2/include/g++-v4 
--enable-languages=c,c++,java
=======================================================================

CORRECT:

=======================================================================
$ ../gcc-4.1.2/configure ${MY_ECONF_OPTS} --build=i686-pc-linux-gnu 
--target=arm-softfloat-linux-gnu --host=arm-softfloat-linux-gnu 
--disable-checking --disable-werror --enable-secureplt 
--disable-libunwind-exceptions --disable-nls --with-float=soft 
--with-cpu=arm920t 
--with-gxx-include-dir=/usr/lib/gcc/arm-softfloat-linux-gnu/4.1.2/include/g++-v4 
--enable-languages=c,c++,java
=======================================================================

For those interested, MY_ECONF_OPTS was from 'man 5 ebuild' (under 
econf), and the rest came from /usr/portage/eclass/toolchain.eclass.
I removed --with-system-zlib because it caused a cross-compile error.

The error that I ran into when i mistakenly issued CFLAGS as an 
environment variable was:

=======================================================================
$ make
(everything works normally until getting to libiberty [Edit:2nd time])
...
Configuring in build-i686-pc-linux-gnu/libiberty
configure: creating cache ../config.cache
checking whether to enable maintainer-specific portions of Makefiles... no
checking for makeinfo... makeinfo --split-size=5000000
checking for perl... perl
checking build system type... i686-pc-linux-gnu
checking host system type... i686-pc-linux-gnu
checking for i686-pc-linux-gnu-ar... i686-pc-linux-gnu-ar
checking for i686-pc-linux-gnu-ranlib... i686-pc-linux-gnu-ranlib
checking for i686-pc-linux-gnu-gcc... gcc
checking for suffix of object files... configure: error: cannot compute 
suffix of object files: cannot compile
See `config.log' for more details.
make[1]: *** [configure-build-libiberty] Error 1
=======================================================================

With config.log saying:

=======================================================================
configure:2251: checking for suffix of object files
configure:2272: gcc -c -O2 -mcpu=arm920t   conftest.c >&5
`-mcpu=' is deprecated. Use `-mtune=' or '-march=' instead.
conftest.c:1: error: bad value (arm920t) for -mtune= switch
configure:2275: $? = 1
=======================================================================

Note to self: do not set a CFLAGS environment variable when 
cross-compiling gcc, if CFLAGS is to have _any_ architecture dependent 
flags!

It's too bad that gcc doesn't use BUILD_CFLAGS and HOST_CFLAGS. I think 
Python does that, no?

At least now I understand why libiberty is compiled twice though. I've 
been doing this stuff for years, and I still am finding out really 
crucially important things today!

Thanks for the replies - sorry if I've confused anyone.

~/Chris


Mike Frysinger wrote:
> On Saturday 01 September 2007, Peter Stuge wrote:
>> On Thu, Aug 30, 2007 at 06:03:58PM -0400, Mike Frysinger wrote:
>>> is_crosscompile is used to detect whether we're building a
>>> cross-compiler, not whether we're cross-compiling the compiler
>> Suggest name change to is_crosscompiler
>
> makes sense
>
>>>> The point is though, that even for straight cross-compiles it's
>>>> usually more dependent on CHOST being set to a different
>>>> architecture than CTARGET.
>>> in the normal case, CTARGET is never set ... however, for all
>>> toolchain based packages, the three tuples (CBUILD CHOST CTARGET)
>>> are made sure to be set to the correct value
>> What about those --enable-serial-* though? Is there a better
>> solution for the author's problem?
>
> i really dont have an idea of what the problem is.  i build cross-compilers
> and cross-compile native compilers and cross-compile cross-compilers and have
> yet to hit any problems (which are not fixed in the current tree).
> -mike
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