在VS Code tasks.json 并安装了C/C++构建工具扩展时，工作区变量如 ${config:aga} 或 ${global} 会在 args 数组项中被替换为它们的值，前提是 type 键为 cppbuild，且不是 shell。

但此类变量不会在 command 键中被替换，因此如果存在：

    "command":"firstText ${variable} thirdText"

其中 ${variable} 等于 secondText，VS Code将字面执行 firstText ${variable} thirdText 命令，而不是 firstText secondText thirdText。

这会在 tasks.json 中的 type 键被设置为 cppbuild 时发生。如果我把 type 设置为 shell，则 command 中的变量会被替换。

变量能在 "type":"cppbuild" 中工作吗？

不起作用的 tasks.json 示例：

{
    "tasks": [
        {
            "type": "cppbuild",
            "label": "C/C++: cl.exe build active file",

            // does not replaced
            "command": "\"C:/Program Files (x86)/Microsoft Visual Studio/18/BuildTools/VC/Tools/MSVC/14.50.35717/bin/Hostx64/${config:arch}/cl.exe\"",  

            // replaced  
            "args": [
                "/Zi",
                "/EHsc",
                "/nologo",
                "/Fe${fileDirname}\\${fileBasenameNoExtension}.exe",
                "${file}",
                "/link /LIBPATH:\\\"C:/Program Files (x86)/Microsoft Visual Studio/18/BuildTools/VC/Tools/MSVC/14.50.35717/lib/${config:arch}\\\" /LIBPATH:\\\"C:/Program Files (x86)/Windows Kits/10/Lib/10.0.19041.0/um/${config:arch}\\\" kernel32.lib user32.lib gdi32.lib winspool.lib comdlg32.lib advapi32.lib shell32.lib ole32.lib oleaut32.lib Uuid.lib odbc32.lib odbccp32.lib /LIBPATH:\\\"C:/Program Files (x86)/Windows Kits/10/Lib/10.0.19041.0/ucrt/${config:arch}\\\"",
                "/SUBSYSTEM:WINDOWS",
                "/ENTRY:mainCRTStartup"
            ],
            "options": {
                "cwd": "${fileDirname}"
            },
            "problemMatcher": [
                "$msCompile"
            ],
            "group": {
                "kind": "build",
                "isDefault": true
            },
            "detail": "Task generated by Debugger."
        }
    ],
    "version": "2.0.0"
}

解决方案

当前的变通做法是将实际的 command 移到 arguments 数组中（因为对于参数，变量会被替换，正如我所写的）：

{
    "tasks": [
        {
            "type": "cppbuild",
            "label": "C/C++: cl.exe build active file",

            "command": "",  

            "args": [
                "\"C:/Program Files (x86)/Microsoft Visual Studio/18/BuildTools/VC/Tools/MSVC/14.50.35717/bin/Hostx64/${config:arch}/cl.exe\"",

                "/Zi",
                "/EHsc",
                "/nologo",
                "/Fe${fileDirname}\\${fileBasenameNoExtension}.exe",
                "${file}",
                "/link /LIBPATH:\\\"C:/Program Files (x86)/Microsoft Visual Studio/18/BuildTools/VC/Tools/MSVC/14.50.35717/lib/${config:arch}\\\" /LIBPATH:\\\"C:/Program Files (x86)/Windows Kits/10/Lib/10.0.19041.0/um/${config:arch}\\\" kernel32.lib user32.lib gdi32.lib winspool.lib comdlg32.lib advapi32.lib shell32.lib ole32.lib oleaut32.lib Uuid.lib odbc32.lib odbccp32.lib /LIBPATH:\\\"C:/Program Files (x86)/Windows Kits/10/Lib/10.0.19041.0/ucrt/${config:arch}\\\"",
                "/SUBSYSTEM:WINDOWS",
                "/ENTRY:mainCRTStartup"
            ],
            "options": {
                "cwd": "${fileDirname}"
            },
            "problemMatcher": [
                "$msCompile"
            ],
            "group": {
                "kind": "build",
                "isDefault": true
            },
            "detail": "Task generated by Debugger."
        }
    ],
    "version": "2.0.0"
}

工作区变量 ${config:variableName} 来自项目中 .vscode 文件夹内的 settings.json 文件。