libstdc++.so: error adding symbols: File in wrong format - linux

Question

I'm trying to build my own library. It worked on x86 linux so I wanna build for MIPS Linux (Little endian.)
I'm using sourcery codebench in Mento Graphics and buildroot and CMake.
I configured build_all.sh like below.
#!/bin/bash -ev
export TARGETROOT="/usr/mipsel-buildroot-linux-gnu/sysroot"
mkdir -p mips_build
cd mips_build
cmake -DCMAKE_SYSTEM_NAME="Linux" \
-DCMAKE_C_COMPILER="${CROSS_COMPILE}gcc" \
-DCMAKE_CXX_COMPILER="${CROSS_COMPILE}g++" \
-DCMAKE_AR="${CROSS_COMPILE}ar" \
-DCMAKE_C_FLAGS="-EL -c -g -O2 -fPIC --sysroot=$TARGETROOT " \
-DCMAKE_CXX_FLAGS="-EL -c -g -O2 -fPIC --sysroot=$TARGETROOT " \
../
make
cd ..
Where $CROSS_COMPILE=/home/vagrant/bd1/mips-2014.05/bin/mips-linux-gnu-
And CMakeFiles.txt is like below.
make_minimum_required (VERSION 2.6)
set(EMSG_INCLUDE_DIR ${CMAKE_CURRENT_SOURCE_DIR}/../../src/eagle_msg/include )
set(EMSG_LIB_DIR ${CMAKE_CURRENT_SOURCE_DIR}/../../lib )
set (PROJECT_SOURCE_DIR ${CMAKE_CURRENT_SOURCE_DIR}/src)
set (PROJECT_INCLUDE_DIR ${CMAKE_CURRENT_SOURCE_DIR}/include)
set (PROJECT_LIB_DIR ${CMAKE_CURRENT_SOURCE_DIR}/lib)
set(LIBRARIES
libemsg.a
libzmq.a
libprotobuf.a
libprotobuf-c.a
libpthread.a
libstdc++.a
)
#For controller : Client
SET(EXECUTABLE test_controller)
project (${EXECUTABLE})
include_directories(
${PROJECT_INCLUDE_DIR}
${EMSG_INCLUDE_DIR}
$ENV{TARGETROOT}/usr/include
)
link_directories(
${PROJECT_LIB_DIR}
${EMSG_LIB_DIR}
$ENV{TARGETROOT}/usr/lib
)
set(SRCS
test_controller.cpp
)
add_executable( ${EXECUTABLE} ${SRCS})
target_link_libraries( ${EXECUTABLE} ${LIBRARIES} )
Then it makes the error like below.
[ 40%] Built target emsg
Linking CXX executable ../../../bin/test_controller
/usr/mipsel-buildroot-linux-gnu/sysroot/usr/lib/libstdc++.so: error adding symbols: File in wrong format
collect2: error: ld returned 1 exit status
make[2]: *** [../bin/test_controller] Error 1
make[1]: *** [test/emsg_test/CMakeFiles/test_controller.dir/all] Error 2
So I checked the format of libstdc++.so. Then it's ELF 32-bit LSB shared object, MIPS, MIPS32. That's the right version. Then what can I do to solve?
/usr/mipsel-buildroot-linux-gnu/sysroot# file /usr/mipsel-buildroot-linux-gnu/sysroot/usr/lib/libstdc++.*
/usr/mipsel-buildroot-linux-gnu/sysroot/usr/lib/libstdc++.a: current ar archive
/usr/mipsel-buildroot-linux-gnu/sysroot/usr/lib/libstdc++.so: symbolic link to `libstdc++.so.6.0.19'
/usr/mipsel-buildroot-linux-gnu/sysroot/usr/lib/libstdc++.so.6: symbolic link to `libstdc++.so.6.0.19'
/usr/mipsel-buildroot-linux-gnu/sysroot/usr/lib/libstdc++.so.6.0.19: ELF 32-bit LSB shared object, MIPS, MIPS32 rel2 version 1 (SYSV), dynamically linked, with unknown capability 0xf41 = 0x756e6700, not stripped
New information
It seems to be the problem of buildroot. I checked the sysroot value of mips-linux-gnu-gcc.
This is the result before installing buildroot.
$ mips-linux-gnu-gcc --print-sysroot
/home/vagrant/bd1/mips-2014.05/bin/../mips-linux-gnu/libc
This is the result after installing buildroot.
$ mips-linux-gnu-gcc --print-sysroot
/usr/usr/mipsel-buildroot-linux-gnu/sysroot/soft-float/el
I also found the post about similar problem. But it's old issue.

Answer 1

Please use the CMake toolchain file provided by Buildroot. It is generated in $(HOST_DIR)/usr/share/buildroot/toolchainfile.cmake. Use it this way:
cmake -DCMAKE_TOOLCHAIN_FILE=/path/to/host/usr/share/buildroot/toolchainfile.cmake
And then you can remove all your other -DCMAKE_ variable, since the toolchain file indicates to CMake which compiler to use, which flags, etc.

Answer 2

I found the reason. The main reason is sysroot path. Buildroot organizes all toolchain into $BUILDROOT/output/host/. So you should change the PATH environment like below.
HOST_BINARY="$BUILDROOT/output/host/usr/bin"
PATH="${PATH}:${HOST_BINARY}"
Where $BUILDROOT is the folder where buildroot is extracted.
You should use toolchain below $BUILDROOT/output/host/usr/bin.