更改cpp_properties.json

{
    "configurations": [
        {
            "name": "Linux",
            "includePath": [
                "${workspaceFolder}/**",
                "/usr/include/c++/5/**",
                "/usr/include/x86_64-linux-gnu/c++/5/**",
                "/usr/include/c++/5/backward/**",
                "/usr/lib/gcc/x86_64-linux-gnu/5/include/**",
                "/usr/local/include/**",
                "/usr/lib/gcc/x86_64-linux-gnu/5/include-fixed/**",
                "/usr/include/x86_64-linux-gnu/**",
                "/usr/include/**"
            ],
            "defines": [],
            "compilerPath": "/usr/bin/clang",
            "cStandard": "c11",
            "cppStandard": "c++11",
            "intelliSenseMode": "linux-clang-x64"
        }
    ],
    "version": 4
}

最关键的一点，"cppStandard": "C++11".