如何在lambda表达式C ++中使用goto语句

Question

Is there any way to use goto statement in lambda expression?

#include <iostream>

int main()
{
    auto lambda = []() {
        goto label;
        return;
    };
    lambda();
    return 0;
label:
    std::cout << "hello, world!" << std::endl;
}

I want the console to output hello, world!, but the compiler gives an error:

use of undeclared label 'label'
        goto label;
             ^
1 error generated.

Answer 1

Is there any way to use goto statement in lambda expression?

No. Not to leave the scope of lambda and jump to the enclosing scope. You can only goto a labeled statement inside the lambda, same as if it were any other function.

Having said that, the uses for goto in C++ specifically are few and infrequent. There are other, better , options. I urge you not to reach for goto as the first tool you use.

Answer 2

You can't use goto to move between functions, and a lambda defines a separate function to it's enclosing scope.

From this reference

The goto statement must be in the same function as the label it is referring, it may appear before or after the label.

And the standard, [stmt.goto]

The goto statement unconditionally transfers control to the statement labeled by the identifier. The identifier shall be a label located in the current function.

Answer 3

The goto statement transfers control to the location specified by label. The goto statement must be in the same function as the label it is referring, it may appear before or after the label.

You can instead do this:

#include <iostream>

int main()
{
    auto lambda = []() {
        goto label;        
        return;
label:
        std::cout << "hello, world!" << std::endl;        
    };
    lambda();
    return 0;

}

And it will print "Hello World". See demo .