Question

I’m trying to cross-compile the OpenCV library for using it on an embedded system running Montavista Linux(the system has an ARM926 processor). I’ve managed to configure and generate the makefiles; the sources are built OK, including the 3rd party libraries. The trouble comes at link time. For some reason libtool picks some libraries from the host system (libjpeg, libtiff, libpng) and tries to link them against the ARM9 object files(which evidently is wrong). The error I get is

/usr/lib/libpng12.so: could not read symbols: File in wrong format.

I couldn’t and I still can’t figure out what exactly is wrong with my setup(I even tried to build the library directly on the ARM9 system but unfortunately it has a very small amount of RAM and gcc chokes). I also modified the LD_LIBRARY_PATH envvar to contain the target’s system libraries and exported it before running configure and make.
Below is what I pass to configure:

LDFLAGS="-L/opt/Montavista/pro/devkit/arm/v5t_le/target/usr/lib" CFLAGS="-I/opt
/Montavista/pro/devkit/arm/v5t_le/target/usr/include -fsigned-char -march=armv5te
-mtune=arm926ej-s -ffast-math -fomit-frame-pointer -funroll-loops" CC=/opt/Montavista
/pro/devkit/arm/v5t_le/bin/arm_v5t_le-gcc CXXFLAGS="-fsigned-char -march=armv5te 
-mtune=arm926ej-s -ffast-math -fomit-frame-pointer -funroll-loops" CXX=/opt/Montavista
/pro/devkit/arm/v5t_le/bin/arm_v5t_le-g++ ./configure --host=armv5tl-montavista-linux-
gnueabi --without-gtk --without-v4l --without-carbon --without-quicktime --without-
1394libs --without-ffmpeg --without-imageio --without-python --without-swig --enable-
static --enable-shared --disable-apps --prefix=/home/dev/Development/lib

I found this question on SO but unfortunately it does not provide a solution for me.

I’m using gcc version 4.2.0 (MontaVista 4.2.0-16.0.32.0801914 2008-08-30) on Montavista Linux for ARM(Leopard board powered by a TI DM365), OpenCV 2.0.0. My host system is Ubuntu 10.4.
Any pointers on how to tackle this issue would be of very much help.

Thanks

[UPDATE][SOLVED]: The autotools based method of generating the makefiles for OpenCV 2.0.0 seems to be broken when trying cross-compiling(or for some odd reason it did not work for me). I used the CMake GUI and specified a proper toolchain.cmake file and everything went smooth. See the answer below.

Answer 1

Procedure for cross-compiling OpenCV 2.0 for ARM using CMake GUI

Requirements

• OpenCV 2.0 source tarball
• CodeSourcery ARM cross-compiler v2009q1 or v2010.09(both tested)
• Ubuntu 10.10/11.04 host machine
• CMake >= v2.6 with CMake GUI

Steps

• Unpack somewhere on your host machine the OpenCV tarball; cd to that location and create a build directory

• Open the CMake GUI. Select:

  • Where is the source code:==path to the folder you unpacked the OpenCV tarball
  • Where to build the binaries:==path to the build folder you created in the first step

• Add a new entry named COMPILER_ROOT as a path entry and set its value to the path of your cross compiler e.g. /opt/CodeSourcery/Sourcery_G++_Lite/bin

• Set CMAKE_TOOLCHAIN_FILE to the path of your toolchain file on your host machine; example toolchain.cmake:

  # this one is important
  SET(CMAKE_SYSTEM_NAME Linux)
  #this one not so much
  SET(CMAKE_SYSTEM_VERSION 1)
  
  # specify the cross compiler
  set(COMPILER_ROOT /opt/CodeSourcery/Sourcery_G++_Lite/bin)
  set(CMAKE_C_COMPILER ${COMPILER_ROOT}/arm-none-linux-gnueabi-gcc)
  set(CMAKE_CXX_COMPILER ${COMPILER_ROOT}/arm-none-linux-gnueabi-g++)
  
  # specify how to set the CMake compilation flags
  # CPP
  SET(CMAKE_CXX_FLAGS $ENV{CXX_FLAGS} CACHE FORCE "")
  SET(CMAKE_CXX_FLAGS_DEBUG $ENV{CXX_FLAGS_DEBUG} CACHE FORCE "")
  SET(CMAKE_CXX_FLAGS_RELEASE $ENV{CXX_FLAGS_RELEASE} CACHE FORCE "")
  SET(CMAKE_CXX_FLAGS_RELWITHDEBINFO $ENV{CXX_FLAGS_RELWITHDEBINFO} CACHE FORCE "")
  
  SET(CMAKE_CXX_LINK_FLAGS $ENV{CMAKE_EXE_LINKER_FLAGS} CACHE FORCE "")
  SET(CMAKE_C_LINK_FLAGS $ENV{CMAKE_EXE_LINKER_FLAGS} CACHE FORCE "")
  SET(CMAKE_CXX_LINK_FLAGS_RELEASE $ENV{CMAKE_EXE_LINKER_FLAGS} CACHE FORCE "")
  SET(CMAKE_CXX_LINK_FLAGS_DEBUG $ENV{CMAKE_EXE_LINKER_FLAGS} CACHE FORCE "")
  
  # C
  #SET(CMAKE_C_FLAGS $ENV{C_FLAGS} CACHE FORCE "")
  SET(CMAKE_C_FLAGS_DEBUG $ENV{C_FLAGS_DEBUG} CACHE FORCE "")
  SET(CMAKE_C_FLAGS_RELEASE $ENV{C_FLAGS_RELEASE} CACHE FORCE "")
  SET(CMAKE_C_FLAGS_RELWITHDEBINFO $ENV{C_FLAGS_RELWITHDEBINFO} CACHE FORCE "")
  
  # where is the target environment 
  SET(CMAKE_FIND_ROOT_PATH ${COMPILER_ROOT})
  
  # search for programs in the build host directories
  SET(CMAKE_FIND_ROOT_PATH_MODE_PROGRAM NEVER)
  # for libraries and headers in the target directories
  SET(CMAKE_FIND_ROOT_PATH_MODE_LIBRARY ONLY)
  SET(CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ONLY)
  

• Tweak other settings to your needs e.g.EXECUTABLE_OUTPUT_PATH LIBRARY_OUTPUT_PATH CMAKE_BUILD_TYPE CMAKE_CFLAGS_DEBUG CMAKE_CFLAGS_RELEASE, third party libraries you want to build with etc.

• Press Configure then Generate; check for eventual errors(everything should run smoothly but you never know)
• If everything went OK in the generation phase then cd to the build folder, type make then sit back and relax until the build process is done