Clangd is a language server for C++/C etc. On CentOS 7, I try to use clangd 12 for code auto-completion. Clangd can be easily installed via its binary release.
My failed attempt to use clang binary release
When I run
clangd --version, I see the following error:
clangd_12.0.0/bin/clangd: /lib64/libc.so.6: version `GLIBC_2.18' not found (required by clangd_12.0.0/bin/clangd)
The reason is that the shared library
libc.so is too old for clangd to run.
We need to use a newer version of glibc (at least glibc-2.18).
I tried to clone glibc and build version 2.20 from scratch:
git clone https://mirrors.tuna.tsinghua.edu.cn/git/glibc.git cd glibc git checkout glibc-2.20 cd .. # Note that glibc requires out-source building, i.e., we are forbidden to build glibc inside its source directory. mkdir glibc-build ../glibc/configure --prefix=$HOME/local make -j 16 make install
LD_LIBRARY_PATH. Then things go badly wrong. Every
executable I use segfaults immediately. For example, when I use
ls, it will
zsh: segmentation fault (core dumped) ls -F –color=auto
According to this post, this is caused by version mismatch: the glibc version requried to run the executable is different from what is provided right now.
I tried the glibc-6.18 release tar downloaed from here. The same errors happens when I add
LD_LIBRARY_PATH and run
Build clangd from source
Maybe we need to build llvm project to use clangd. Here is how to compile llvm from source:
git clone --depth=1 https://github.com/llvm/llvm-project.git cd llvm-project mkdir build && cd build cmake -G "Unix Makefiles" -DLLVM_ENABLE_PROJECTS="clang;clang-tools-extra" -DCMAKE_INSTALL_PREFIX=~/tools/llvm -DCMAKE_BUILD_TYPE=Release ../llvm make -j 16 make install
Some explanation about the options used:
-DLLVM_ENABLE_PROJECTS="clang;clang-tools-extra": it specifies which project we want to build. To use
clang-tools-extrais a must.
-DCMAKE_INSTALL_PREFIX=~/tools/llvm: it specifies where we want to install llvm.
-DCMAKE_BUILD_TYPE=Release: it specifies the build type.
Releasetype is smaller than
For more detail on Cmake options when building llvm, check here.
Since llvm is a huge project, it may take a long time to build. It takes 37m to build on my server with 16 concurrent processes.
This time, clangd works without errors. After installing llvm, do not forget to
add llvm binary to your
How to use clangd
According to clangd documentation, you can either generate a
file for your project or use
For simple project, using
compile_flags.txt is sufficient. Your compile flags
are written one per line. A sample
compile_flags.txt looks like this:
-Wall -std=c++11 -L/usr/local/lib -I/usr/local/include -lfmt
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