Clangd is a language server for C++/C etc. I try to use clangd 12 for C++ code auto-completion on CentOS 7.
My failed attempt to use clang binary release
Clangd can be easily installed via its binary release.
However, 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
libc.so on CentOS 7 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 repo 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
After that, I added
Then things went badly wrong: every executable I use segfaults immediately!
For example, when I run
ls, I got an error from the shell:
zsh: segmentation fault (core dumped) ls -F –color=auto
According to this post, this is due to version mismatch: the glibc version required to run the executable is different from what is provided right now.
I tried the glibc-6.18 release tarball downloaded from here.
The same errors happens when I add
LD_LIBRARY_PATH and run
Building clangd from source: success
I also tried to build llvm project from scratch 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 targets we want to build. To use
clang-tools-extrais a must.
-DCMAKE_INSTALL_PREFIX=~/tools/llvm: it specifies where we want to install llvm, in this case, we install it under
-DCMAKE_BUILD_TYPE=Release: it specifies the build type.
Releasetype will be smaller than
For more details about Cmake options on building llvm, check here.
Since llvm is a huge project, it may take quite a while to build. FYI, It takes about 37 minutes to build on my server with 16 parallel processes.
After installing llvm, do not forget to add llvm binary to your
clangd runs without any error.
How to use clangd
According to clangd documentation, you can either generate a
compile_commands.json file for your project or use
For simple project, using
compile_flags.txt is sufficient.
Your compile flags are written one per line.
compile_flags.txt looks like this:
-Wall -std=c++11 -L/usr/local/lib -I/usr/local/include -lfmt
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