在用VS Code开发Linux内核模块时，我偶然发现了一个有趣的行为。
关于c_cpp_properties.json：

{
    "configurations": [
        {
            "name": "Linux",
            "includePath": [
                "${workspaceFolder}/**",
                "/usr/src/linux-headers-5.15.0-91-generic/arch/x86/include",
                "/usr/src/linux-headers-5.15.0-91-generic/arch/x86/include/generated",
                "/usr/src/linux-headers-5.15.0-91-generic/include",
                "/usr/src/linux-headers-5.15.0-91-generic/arch/x86/include/uapi",
                "/usr/src/linux-headers-5.15.0-91-generic/arch/x86/include/generated/uapi",
                "/usr/src/linux-headers-5.15.0-91-generic/include/uapi",
                "/usr/src/linux-headers-5.15.0-91-generic/include/generated/uapi",
                "/usr/src/linux-headers-5.15.0-91-generic/ubuntu/include",
                "/usr/lib/gcc/x86_64-linux-gnu/9/include"
            ],
            "defines": [
                "__GNUC__",
                "__KERNEL__"
            ],
            "compilerPath": "/usr/bin/gcc",
            "cStandard": "c17",
            "cppStandard": "gnu++14",
            "intelliSenseMode": "linux-gcc-x64"
        }
    ],
    "version": 4
}

字符串
一切正常：所有#include <linux/...>都得到正确解决。
关于c_cpp_properties.json：

{
    "configurations": [
        {
            "name": "Linux",
            "includePath": [
                "${workspaceFolder}/**",
                "/usr/src/linux-headers-5.15.0-91-generic/**",
                "/usr/lib/gcc/x86_64-linux-gnu/9/include"
            ],
            "defines": [
                "__GNUC__",
                "__KERNEL__"
            ],
            "compilerPath": "/usr/bin/gcc",
            "cStandard": "c17",
            "cppStandard": "gnu++14",
            "intelliSenseMode": "linux-gcc-x64"
        }
    ],
    "version": 4
}

型
我得到的错误基本上说，几乎所有的，如果不是所有的内核特定的结构，函数和宏是未定义的。

**为什么？**第二个配置应该包含第一个配置的所有路径。