= Toolchains installation =

A cross toolchain is needed to compile on your computer a program for a target (different achitecture). A toolchain is needed to compile on your computer programs for your computer.

All toolchains/cross toolchains only supports x86_64 hosts (32 bits hosts are not supported).

Toolchains have been built with [https://github.com/2rm-robotics/robomap3-rt robomap3] project, based on poky. They package everything you need for flair.

__NOTE__: for sake of simplicity, the word compilation can be used in this documentation for both cross compilation and compilation

== Toolchain for x86_64 (mandatory) ==

You need at least this one, as it used for compiling FlairGCS and other tools.

{{{
$ cd ~
$ wget https://uav.hds.utc.fr/src/toolchain/x86_64-meta-toolchain-flair-x86_64.sh
$ chmod +x x86_64-meta-toolchain-flair-x86_64.sh
$ sudo ./x86_64-meta-toolchain-flair-x86_64.sh
$ rm x86_64-meta-toolchain-flair-x86_64.sh
}}}

== Cross toolchain for armv7a-neon (ardrone2, bebop, hds x8)  ==

{{{
$ cd ~
$ wget https://uav.hds.utc.fr/src/toolchain/x86_64-meta-toolchain-flair-armv7a-neon.sh
$ chmod +x x86_64-meta-toolchain-flair-armv7a-neon.sh
$ sudo ./x86_64-meta-toolchain-flair-armv7a-neon.sh
$ rm x86_64-meta-toolchain-flair-armv7a-neon.sh
}}}

== Cross toolchain for armv5e (mambo)  ==

{{{
$ cd ~
$ wget https://uav.hds.utc.fr/src/toolchain/x86_64-meta-toolchain-flair-armv5e.sh
$ chmod +x x86_64-meta-toolchain-flair-armv5e.sh
$ sudo ./x86_64-meta-toolchain-flair-armv5e.sh
$ rm x86_64-meta-toolchain-flair-armv5e.sh
}}}


== Setup files ==

Each toolchain install 2 important files needed for compilation:
* ''environment-setup-arch-poky-linux-gnueabi'': a script to source if you need to compile something manually, without CMake. For example ''/opt/robomap3/2.1.3/armv5te/environment-setup-armv5e-poky-linux-gnueabi''
* ''toolchain.cmake'': a file used by CMake to get all information needed to compile with this toolchain. For example ''/opt/robomap3/2.1.3/armv5te/toolchain.cmake''

The first one can be used to compile a kernel for example. The second one is needed for each CMake project, but is automatically used by the [wiki:compile_all#Helperscripts helper scripts], so you should not have to bother with it, unless you want to build a CMake project not in the flair build system.

== Environment variable == 

Toolchain installation scripts add variables in ''.bashrc''. If you need to use it directly in the same terminal or an already opened one, reload your ''.bashrc''
{{{
$ source ~/.bashrc
}}}

These variables are:
* ''OECORE_CMAKE_TOOLCHAINS'': a list of installed toolchains (for example ''core2_64 armv7a_neon armv5te'')
* ''OECORE_CMAKE_arch_TOOLCHAIN'': where ''arch'' is from the previous list (for example ''OECORE_CMAKE_CORE2_64_TOOLCHAIN''). Location of the ''toolchain.cmake'' file for a specific architecture
* ''OECORE_HOST_SYSROOT'': used by ground control station to retrieve maps provider plugins (for gps)
* ''OECORE_HOST_NATIVE_SYSROOT'': used to retrieve host's cmake and doxygen tools.

== Installation des drivers graphiques (maybe deprecated) == 

 * Si vous possédez une carte vidéo type nvidia, il faut copier les librairies dans la toolchain:
{{{
$ sudo cp -r /usr/lib/nvidia-340/* /opt/robomap3/1.7.3/core2-64/sysroots/core2-64-poky-linux/usr/lib 
}}}

 * Pour une carte vidéo de type ATI:
{{{
$ sudo cp -r /usr/lib/fglrx/* /opt/robomap3/1.7.3/core2-64/sysroots/core2-64-poky-linux/usr/lib 
}}}

 * For an Intel graphic card, it's a little bit more complicated, due to several versions and path for the libraries.
The idea is that we're using the system video card driver since it's not included in robomap3.

The driver itself (eg: i965_dri.so) should be loaded automatically (from /usr/lib/x86_64-linux-gnu/dri/). But this driver may not succesfully load since it requires some specific library versions that may not match robomap3's.

To debug this you should launch your 3D graphic program (eg: simulator) with the LIBGL_DEBUG environment variable set to verbose. 
For example
{{{
$ LIBGL_DEBUG=verbose ./LineFollower_simulator_nrt -n x4_0 -t x4 -a 127.0.0.1 -p 9000 -x setup_x4.xml (...)
}}}
Notice the line that look like {{{ libstdc++.so.6: version `CXXABI_1.3.9' not found (required by /usr/lib/x86_64-linux-gnu/dri/i965_dri.so) }}}.
This means that the local system driver needs a version of libstdc++.so.6 that defines the symbol CXXABI_1.3.9 (meaning application binary interface version 1.3.9).
The version of libstdc++ included in robomap3 probably doesn't define this symbol. You can make sure with 
{{{
strings /.../robomap3/1.7.3/core2-64/sysroots/core2-64-poky-linux/usr/lib/libstdc++.so.6 | grep CXXABI_ 
}}}
So we need to preload the libstdc++ library of the system to avoid robomap3 one to be loaded. 
To achieve this we need to set the LD_PRELOAD environment variable like this
{{{
LD_PRELOAD=/usr/lib/x86_64-linux-gnu/libstdc++.so.6 ./LineFollower_simulator_nrt ...
}}}


Stopping here may be enough, but you then can see errors like {{{ i965_dri.so: undefined symbol: nouveau_drm_new }}}.

Same problem: the driver needs a version of a library (here libdrm_nouveau.so.2) which defines a specific symbol that doesn't exist in robomap3 version (yet).

Same solution: preload the local system library.
Repeat this until all unresolved symbols are gone.

On ubuntu 16.10 with robomap3 1.7.3, I ended up with the following
{{{
LD_PRELOAD=/usr/lib/x86_64-linux-gnu/libstdc++.so.6:/usr/lib/x86_64-linux-gnu/libdrm_intel.so.1:/usr/lib/x86_64-linux-gnu/libdrm_nouveau.so.2:/usr/lib/x86_64-linux-gnu/libdrm_radeon.so.1  ./LineFollower_simulator_nrt -n x4_0 -t x4 ...
}}}
To avoid setting this variable every time, you can modify the script used to launch the program (usually in build/bin, eg: simulator_xx.sh) and add this line __after__ the first one
{{{
export LD_PRELOAD=/usr/lib/x86_64-linux-gnu/libstdc++.so.6:/usr/lib/x86_64-linux-gnu/libdrm_intel.so.1:/usr/lib/x86_64-linux-gnu/libdrm_nouveau.so.2:/usr/lib/x86_64-linux-gnu/libdrm_radeon.so.1
}}}