c++ - 省略参数名称，C++ vs C

Question

在 C++ 中，在某些情况下，我倾向于省略参数的名称。但是在 C 语言中，当我省略参数的名称时出现错误。

代码如下:

void foo(int);  //forward-decl, it's OK to omit the parameter's name, in both C++ and C

int main()
{
    foo(0);
    return 0;
}

void foo(int)  //definition in C, it cannot compile with gcc
{
    printf("in foo\n");
}

void foo(int)  //definition in C++, it can compile with g++
{
    cout << "in foo" << endl;
}

这是为什么呢？ C函数定义中不能省略参数名吗？

Answer 1

不，在 C 中，您不能在函数定义中省略参数标识符。

C99 标准说:

[6.9.1.5] If the declarator includes a parameter type list, the declaration of each parameter shall include an identifier, except for the special case of a parameter list consisting of a single parameter of type void, in which case there shall not be an identifier. No declaration list shall follow.

C++14 标准说:

[8.3.5.11] An identifier can optionally be provided as a parameter name; if present in a function definition , it names a parameter (sometimes called “formal argument”). [Note: In particular, parameter names are also optional in function definitions and names used for a parameter in different declarations and the definition of a function need not be the same.]