解决办法，注释掉 launch.json 中的  "externalConsole": false,

完整 launch.json

{
    // 使用 IntelliSense 了解相关属性。 
    // 悬停以查看现有属性的描述。
    // 欲了解更多信息，请访问: https://go.microsoft.com/fwlink/?linkid=830387
    "version": "0.2.0",
    "configurations": [
        {
            "name": "gcc.exe - 生成和调试活动文件",
            "type": "cppdbg",
            "request": "launch",
            "program": "${fileDirname}\\${fileBasenameNoExtension}.exe",
            "args": [],
            "stopAtEntry": false,
            "cwd": "${workspaceFolder}",
            "environment": [],
            // "externalConsole": true,
            "MIMode": "gdb",
            "miDebuggerPath": "C:\\mingw64\\bin\\gdb.exe",
            "setupCommands": [
                {
                    "description": "为 gdb 启用整齐打印",
                    "text": "-enable-pretty-printing",
                    "ignoreFailures": true
                }
            ],
            "preLaunchTask": "mingw_task",
        }
    ]
}

额外附上我的 task.json

{
	"version": "2.0.0",
	"tasks": [
		{
			"type": "shell",
			"label": "mingw_task",
			"command": "C:\\cygwin64\\bin\\g++.exe",
			"args": [
				"-g",
				"${file}",
				"-o",
				"${fileDirname}\\${fileBasenameNoExtension}.exe"
			],
			"options": {
				"cwd": "C:\\mingw64\\bin"
			},
			"problemMatcher": [
				"$gcc"
			],
			"group": "build"
		}
	]
}