c++ - 可以省略 main 函数中的返回类型吗？

Question

这个问题在这里已经有了答案:

What should main() return in C and C++? (19 个回答)

关闭 6年前。

main函数的声明有什么特殊的规则吗？

根据ideone这是合法的 C++:

main()  // As opposed to int main()
{
   return 0;
}

另一方面，普通函数似乎没有特权避免返回类型:

f(){} 

int main()
{
    return 0;
}

给出错误:

prog.cpp:1:3: error: ISO C++ forbids declaration of 'f' with no type [-fpermissive] f(){} ^

main函数在这种情况下有什么特殊吗？

Answer 1

永远不要省略 main 的返回类型，因为它是非标准的!

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wandbox example :

prog.cc:1:6: warning: ISO C++ forbids declaration of 'main' with no type [-Wpedantic] main()

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From $3.6.1 :

1 A program shall contain a global function called main, which is the designated start of the program. It is implementation-defined whether a program in a freestanding environment is required to define a main function. [ Note: In a freestanding environment, start-up and termination is implementation-defined; startup contains the execution of constructors for objects of namespace scope with static storage duration; termination contains the execution of destructors for objects with static storage duration. — end note ] § 3.6.1 58

2 An implementation shall not predefine the main function. This function shall not be overloaded. It shall have a return type of type int, but otherwise its type is implementation-defined