libstdc++ and --with-sysroot

[Andrew Haley]

Jon Dufresne wrote:
> On Tue, Nov 18, 2008 at 11:13 AM, Andrew Haley <aph@redhat.com> wrote:
>> Jon Dufresne wrote:
>>
>>> I am creating a cross toolchain using gnu. So far it has been working great.
>>>
>>> However, one problem I noticed is that libstdc++ isn't installed into
>>> the specified sysroot duing "make install".
>>>
>>> After I have binutils, a static gcc, linux-headers, and glibc compiled
>>> this is how I build gcc:
>>>
>>> ${BUILD}/gcc-${GCC_VERSION}/configure \
>>>                       --prefix=${TOOLS} \
>>>                       --build=${HOST} \
>>>                       --host=${HOST} \
>>>                       --target=${TARGET} \
>>>                       --with-sysroot=${ROOTFS} \
>>>                       --enable-languages=c,c++ \
>>>                       --disable-multilib \
>>>                       --disable-nls \
>>>                       --enable-shared \
>>>                       --enable-threads=posix \
>>>                       --enable-__cxa_atexit \
>>>                       --disable-libunwind-exceptions \
>>>                       --enable-c99 \
>>>                       --enable-long-long
>>>
>>> make
>>> make install
>>>
>>> The things to notice are that I use the "--with-sysroot" option and enable c++.
>>>
>>> After the compile finishes libstdc++ is installed to
>>> ${TOOLS}/${TARGET}/lib and I need to manually copy it over to the
>>> ${ROOTFS}/usr/lib. Is this a bug in the gcc Makefile? Should libstdc++
>>> install to the sysroot by default like the c runtime library does? Or
>>> is this preferred behavior?
>> It's doing what it's supposed to do.  All target libs are installed in
>> the prefix, along with the cross-compiler.  The libs have to be there because
>> the cross-compiler needs them.
>>
>> So, you need the target libs in two places: in /usr/lib on the target and
>> in prefix/*lib on the cross compiling host.
> 
> Makes sense, but why doesn't the Makefile install the target libs into
> both places, since that is what is needed?

Because usually the place you have to install the target libs is not the
sysroot but /usr/lib on the target machine: the target machine may be
in another building or even on another planet.  How you get the target
libs to the target is up to you; it may involve burning a CD, an FTP
transfer, or a carrier pigeon.  ;-)

> Copying them manually is
> easy enough, but if they libraries are required in two places, it
> seems the installation should put them in two places.

Sure, but the sysroot isn't the other place!  The sysroot is used when
building the cross-compiler as the source for target libs and headers;
the destination is the prefix.

Andrew.