dots/.config/nvim/coc-settings.json

{
    "languageserver": {
        "ccls": {
            "command": "ccls",
            "args": ["--log-file=/tmp/ccls.log", "-v=1"],
            "filetypes": ["c", "cc", "cpp", "c++", "objc", "objcpp"],
            "rootPatterns": [".ccls", "compile_commands.json", ".git/", ".hg/"],
            "initializationOptions": {
                "cache": {
                    "directory": "/tmp/ccls"
                },
                "index": {
                    "onChange": true
                },
                "highlight": {
                    "lsRanges": true
                }
            }
        }
    }
}