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nerves-toolchain

This project contains the configuration and scripts used to build the cross-compilers for the Nerves project. While pre-built toolchains exist for various hosts and targets, they don't seem to exist for the combination supported by Nerves. This project fills that gap.

See the GitHub Releases tab to download the toolchain. The naming for toolchains is:

nerves-toolchain-<gcc tuple>-<host OS>-<host architecture>-<version>.tar.xz

The gcc tuple is a standard way of describing a target. The most important parts are the architecture (e.g., arm) and the C Library and ABI (e.g., gnueabihf). You will receive an error from Nerves if you mix toolchains. The easy way to decide which toolchain you need is the following:

  • Raspberry Pi Model A+, B, or B+ - armv6-nerves-linux-gnueabihf
  • Raspberry Pi 2, BBB, and most other ARM boards - armv7-nerves-linux-gnueabihf

The host OS and host architecture describe your system. If you're running on a Mac, this is Darwin-x86_64 or Darwin-arm64.

When in doubt, use the glibc library toolchains. Almost all code works with the glibc C library. If you desire the smallest possible target binaries, the musl toolchain is the way to go. Nerves has been lightly tested against it, but it is an experimental feature and not built by default due to issues on OSX.

Linux

Install the following packages:

sudo apt install build-essential bison flex gperf libncurses5-dev texinfo help2man libssl-dev gawk libtool-bin automake lzip unzip python3 wget curl ca-certificates

Run build_release.sh and wait.

OSX

Install the following packages:

brew update
brew install gawk binutils xz wget automake gnu-tar help2man bash make ncurses libtool autoconf gnu-sed mpfr gmp gcc bison lzip python3 grep coreutils texinfo

Run build_release.sh and wait.

Windows

Windows toolchains are not supported yet

Install Chocolatey. Then, from a command prompt with administrative privileges (not the same one that you installed Chocolatey), run:

choco install cyg-get
cyg-get autoconf make gcc-g++ gperf bison flex texinfo awk wget curl patch libtool automake diffutils libncurses-devel help2man libssl-dev ca-certificates
cyg-get mingw64-i686-gcc-g++ mingw64-x86_64-gcc-g++ #??

Enable case-sensitive filesystem support on NTFS using the registry: (https://cygwin.com/cygwin-ug-net/using-specialnames.html)

HKLM\SYSTEM\CurrentControlSet\Control\Session Manager\kernel\obcaseinsensitive=0

Then tell Cygwin to mount your cygdrive as case sensitive. In a Cygwin64 terminal, edit /etc/fstab and set posix=1 in the mount options. For example:

none /cygdrive cygdrive binary,posix=1,user 0 0

Something didn't work for me when downloading the ca-certificates. This will cause https downloads to fail. To fix, here's what I did:

rm /usr/ssl/certs/ca-bundle.crt
ln -s /etc/pki/ca-trust/extracted/pem/tls-ca-bundle.pem /usr/ssl/certs/ca-bundle.crt
echo "ca_directory = /usr/ssl/certs" > ~/.wgetrc

Reboot to make the registry change take effect.

NOTE: Windows is a work in progress. The link step segfaults. The following doc may provide some help.

Updating ctng config files

You may need to update the ctng configurations if gcc needs to be upgraded or the C library needs to change. The small defconfigs are stored in the configs directory and expanded automatically by build.sh to work-.../build/.config. In that directory, you can run make menuconfig to change the ctng configuration. When you're done, run make savedefconfig and copy the result to the configs directory.

Toolchain configuration notes

Hard float vs. soft float

When possible hard float ABI (eabihf) toolchains are preferred. This appears to be the prevaling preference for ARM toolchains, so in the offchance that we need to run code from a binary blob, this provides the best chance of success. For ARM processors that don't have hardware floating point instructions, use the eabi versions of the ARM toolchain.

Glibc 2.22 / Raspberry Pi userland

Glibc 2.22 has a #define change that breaks the Raspberry Pi userland (rpi-userland) package. You'll get an error that EAI_AGAIN and some other defines are missing due to a #ifdef that changed from __USE_POSIX to _USE_XOPEN2K. Do NOT select glibc 2.22 until rpi-userland is fixed.

See https://bugs.busybox.net/show_bug.cgi?id=8446 for more details.

Case insensitive filesystems

By default, the filesystems used on OSX are case insensitive. To get around this, we create a case-sensitive filesystem and build the cross-compilers in it. The build products also require a case-sensitive filesystem IF the user wants to use the Linux netfilter module. This is currently not a common use case for Nerves so the header file conflicts are removed in the OSX tarball version. See build.sh for details.

License

For the most part this code contains configurations and automates calls to other projects, notably crosstool-ng. The build.sh script is licensed under the Apache 2 License. Please see the numerous integrated projects for their licenses.

scripts/apply-patches.sh is from the Buildroot project and is released under the GNU General Public License, version 2 or later.