gnulibs

Generate tarballs for GNU C++ and support libraries for many targets.

What is this?

This script uses crosstool-ng to generate a basic GCC cross-compiler, and uses this to compile:

libstdc++
libgcc
libatomic

It then packages the generated artifacts, removes unnecessary files, and generates a tarball with only the libraries and GNU STL headers.

Why?

The intended use-case is with zig cc. The Zig compiler ships with enough sources to compile LLVM's libc++ and compiler_rt on-demand for the given target, which is extremely useful. However, in cases where linking with pre-compiled shared libraries that use the GNU STL ABI is required, this is not sufficient. zig cc does not support Clang's -stdlib=libstdc++ flag, because there is no reasonable way to support it with the way zig cc works ( "Building libstdc++ separately from the rest of GCC is not supported.")

Doing -nostdinc++ -nostdlib++ -I... -L... -lstdc++ works; however, it:

Adds system dependencies to your build (zig cc is mostly-hermetic)
Does not work when cross-compiling to other targets

The use-case I am trying to solve involves using hermetic_cc_toolchain together with Bazel to cross-compile a project. However, since there are pre-existing binaries with the GNU STL ABI as mentioned above, this becomes impossible. This project is intended to solve this.

Requirements

You need the following on your system:

bash
coreutils (GNU coreutils tested)
wget or curl
Either Clang or GCC (in essence, a C/C++ compiler that can compile GCC)

Usage

Just running ./build.sh should be sufficient. Currently, tarballs for the following targets are built:

aarch64-linux-gnu
x86_64-linux-gnu

To use these libraries, you will need the following compile flags:

-nostdinc++ -nostdlib++ -nodefaultlibs (prevent your compiler from automatically linking in your system libraries)
Include paths:
- -isystem path/to/gnulibs/include
- -isystem path/to/gnulibs/include/backward
- -isystem path/to/gnulibs/include/target (This is renamed to be target-independent)

You also need these link flags:

-nostdinc++ -nostdlib++ -nodefaultlibs
Library path: -Lpath/to/gnulibs/lib
The libraries you need: -lc -lgcc -lstdc++ -latomic
- Might make sense to use -Wl,--as-needed to reduce the amount you have to link.
When linking shared objects/dynamic executables, add -lgcc_s
When linking a static binary, add -lgcc_eh

TODO: Add documentation on how to use this together with zig cc (requires further testing)

License

The contents of the generated tarballs are under the same license as libstdc++ (GNU General Public License version 3, with the GCC Runtime Library Exception version 3.1).