On Tuesday, LLVM announced that starting from LLVM 7, the packages libc++, libc++abi, and OpenMP are integrated into llvm-toolchain. Integration of these libraries was a project proposed in the Google Summer of Code 2018.
Warnings and usage of the libc++* and OpenMP packages
libc++* packages
The libc++ and libc++abi packages that are currently present in Debian and Ubuntu repositories will not be affected, but they will be removed in the later versions. Also, the newly integrated libcxx* packages are not co-installable with them.
To keep the library usage same as before, symlinks are provided from the original locations. For example, from /usr/lib/x86_64-linux-gnu/libc++.so.1.0 to /usr/lib/llvm-7/lib/libc++.so.1.0.
The usage of libc++ is as follows:
$ clang++-7 -std=c++11 -stdlib=libc++ foo.cpp
$ ldd ./a.out|grep libc++
libc++.so.1 => /usr/lib/x86_64-linux-gnu/libc++.so.1 (0x00007f62a1a90000)
libc++abi.so.1 => /usr/lib/x86_64-linux-gnu/libc++abi.so.1 (0x00007f62a1a59000)OpenMP packages
Though OpenMP has been a part of Debian and Ubuntu archives, only one version was supported on the system. To address this, OpenMP is integrated with the llvm-toolchain.
Similar to libc++, to keep the current usage same, the newly integrated package creates a symlink from /usr/lib/libomp.so.5 to /usr/lib/llvm-7/lib/libomp.so.5.
It can be used with clang through -fopenmp flag:
$ clang -fopenmp foo.cThe dependency packages that provide the default libc++* and OpenMP package are also integrated into llvm-defaults. Using the following command you will able to install the current version of all these packages:
$ apt-get install libc++-dev libc++abi-dev libomp-devTo get more clarity on the integration of libc++* and OpenMP in llvm-toolchain, check out their announcement on LLVM’s site.
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