[C++] Fail to find headers under /usr/include/c++/x/

[Maverobot]

I have been using lsp-ccls as the c++ backend for a long time. Today it suddenly cannot find any standard headers anymore (array, algorithm, etc). I switched to clangd but the same issue stays. Note that all project-local headers can still be found by the ccls and clangd.

I chatted with @yyoncho on gitter.im and we failed to locate the issue.

Does anyone have the same issue or can help me to fix it?

Hi @danielmartin : @yyoncho meant that you can be a great help for this topic :)

[danielmartin]

What operating system do you use? I'm not very familiar with ccls, but with clangd you can pass the -log=verbose flag to get more information about the system includes and any problems accessing them.

[Maverobot]

I am using Ubuntu 18.04. Thanks for the tip! I will follow the troubleshooting page from clangd and post the result.

[Maverobot]

I think I found the issue but have no idea how to solve it. It seems that clang cannot find the standard library header.

Run

clang --driver-mode=g++ -Wall -Wextra -pedantic -std=gnu++1z -o CMakeFiles/attributes_example.dir/src/attributes_example.cpp.o -c ~/Sandbox/cpp_playground/cpp_practices/attributes_example/src/attributes_example.cpp -working-directory=~/Sandbox/cpp_playground/cpp_practices/attributes_example/build

I got

fatal error: 'algorithm' file not found

On another PC where I have the "same" setup, the above command works without any issue.

[Maverobot]

Fixed.

It seems that I just had to do sudo apt remove libgcc-11-dev. A similar issue can be found here:

https://stackoverflow.com/questions/54521402/locating-iostream-in-clang-fatal-error-iostream-file-not-found

[sreegowthamj]

Regarding the missing system include files in the compile_commands.json file generated, we can have clangd append additional include directories by adding a global / project specific config file as mentioned here - https://clangd.llvm.org/config.html#add .
The config files are loaded alongside the compile_commands.json file and can be used to add/remove/modify/remap compilation flags.