c++ compile error 'expected ';' at end of declaration' when using direct brace initialization

问题

I'm very new to C++, working through my first tutorial, and when I try to compile code from the lesson, I get the following error:

expected ';' at end of declaration
    int x{ }; // define variable x to hold user input (a...
         ^
         ;

The full code for the program I'm attempting to run:

#include <iostream>  // for std::cout and std::cin
 
int main()
{
    std::cout << "Enter a number: ";
    int x{ }; 
    std::cin >> x; 
    std::cout << "You entered " << x << '\n';
    return 0;
}

I am using Visual Studio Code (v.1.46.1) on a Macbook Pro, with the Microsoft C/C++ extension (https://marketplace.visualstudio.com/items?itemName=ms-vscode.cpptools).

My compiler is Clang:

Apple clang version 11.0.3 (clang-1103.0.32.62)
Target: x86_64-apple-darwin19.5.0
Thread model: posix
InstalledDir: /Library/Developer/CommandLineTools/usr/bin

Initially, I ran Terminal > Configure Default Build Task in VS Code to create a .vscode/tasks.json compiler settings file. That file currently looks like this:

{
    "version": "2.0.0",
    "tasks": [
    {
      "type": "shell",
      "label": "C/C++: clang++ build active file",
      "command": "/usr/bin/clang++",
      "args": [
        // Set C++ Standards 
        "-std=c++17",

        // Increase compiler warnings to maximum
        "-Wall",
        "-Weffc++",
        "-Wextra",
        "-Wsign-conversion",

        // Treat all warnings as errors
        "-Werror",

        // Disable compiler extensions
        "-pedantic-errors",

        // File to compile
        "-g",
        "${file}",

        // Output file
        "-o",
        "${fileDirname}/${fileBasenameNoExtension}"
      ],
      "options": {
        "cwd": "${workspaceFolder}"
      },
      "problemMatcher": [
        "$gcc"
      ],
      "group": {
        "kind": "build",
        "isDefault": true
      }
    }
  ]
}

I have the -std=c++17 flag set, which should allow direct brace initialization from what I understand.

I'm not sure it matters, since I'm trying to compile and not build/debug, but for the sake of thoroughness, I also have a .vscode/launch.json file with the following contents:

{
  "version": "0.2.0",
  "configurations": [
    {
      "name": "clang++ - Build and debug active file",
      "type": "cppdbg",
      "request": "launch",
      "program": "${fileDirname}/${fileBasenameNoExtension}",
      "args": [],
      "stopAtEntry": true,
      "cwd": "${workspaceFolder}",
      "environment": [],
      "externalConsole": false,
      "MIMode": "lldb",
      "preLaunchTask": "C/C++: clang++ build active file"
    }
  ]
}

Can someone help me figure out why int x{ }; is not working properly to intitialize the variable and what I can do to fix it so it will work?

[Edit]: Further settings I've checked/tested:

• Code compiles correctly when running compile directly from command line with clang++ -std=c++17 -g helloworld.cpp -o helloworld
• VS Code C/C++ extension configuration has setting 'C++ standard' set to c++17 (seems to be the default). Even so, running command-line compile without -std=c++17 flag set causes same compiler error.
• Tried changing int x{ }; to the following:
  • int x( );: fails with a very long list of errors
  • int x(0);: compiles successfully
  • int x = { };: compiles successfully
  • int x = {0};: compiles successfully
  • `int x;': compiles successfully
  • `int x = 0;': compiles successfully

回答1:

Refering to this explanation of List initialization, this syntax should be legal since c++11:

int main()
{
    int n0{};     // value-initialization (to zero)
    int n1{1};    // direct-list-initialization
    //...
}

I attempted to compile your code in my local environment and all worked fine:

clang++ -std=c++17 -Wall -Weffc++ -Wextra -Wsign-conversion -Werror -pedantic-errors ...

clang++ --version
clang version 9.0.1 
Target: x86_64-pc-linux-gnu
Thread model: posix

Maybe you used some similar ';' character which is not ASCII?
I attempted to use a Chinese character '；' instead and get this:

fly.cc:32:13: error: treating Unicode character <U+FF1B> as identifier character rather than as ';' symbol [-Werror,-Wunicode-homoglyph]
    int x{ }； 
            ^~
fly.cc:32:13: error: expected ';' at end of declaration
    int x{ }； 
            ^
            ;

来源：https://stackoverflow.com/questions/62487546/c-compile-error-expected-at-end-of-declaration-when-using-direct-brace-i