Comment # 5 on bug 1199943 from Aaron Puchert

(In reply to Andreas Nordal from comment #0)
> /tmp/compile_commands.json:
> 
>     [{
>       "directory": "/tmp",
>       "command": "g++ -std=c++17 -Iweird_include -c takes_string_view.cpp -o
> takes_string_view.o",
>       "file": "takes_string_view.o"
>     }]

The "file" needs to be "takes_string_view.cpp" [1]:

> file: The main translation unit source processed by this compilation step.
> This is used by tools as the key into the compilation database. There can be
> multiple command objects for the same file, for example if the same source
> file is compiled with different configurations.

Then -std=c++17 is passed through. Possibly clangd thinks that since
takes_string_view.o does not have a C++ source file ending, an option like
-std=c++17 has to be dropped. (Clang can also process other files, such as
assembly .s, LLVM IR .ll/.bc and some more.)

[1] https://clang.llvm.org/docs/JSONCompilationDatabase.html#format