没有定义的函数参数的默认值类型为int？我是疯了吗？ [英] No defined type of a function parameter defaults to int? Am I insane?

问题描述

对于一些奇怪的原因，我是在复制其不使用的类型，忘了添加一个到一个函数定义参数的另一种语言的例子，它的工作。

For some odd reason I was copying an example in another language of which does not use types, and forgot to add one in to a function definition parameter, and it worked.

#include <stdio.h>

char toChar(n) {
  //sizeof n is 4 on my 32 bit system
  const char *alpha = "0123456789ABCDEF";
  return alpha[n];
}

int main() {
  putchar(toChar(15)); //i.e.
  return 0;
}

我相信主默认是通过一些标准（但只返回）的大多数编译器诠释，这是也是一个行为的其他功能也同样如此或定义此实现？这似乎只是与众不同，我的编译器只是一个稍微过时的GCC端口（MinGW的）。

I am sure that main defaults to int by most compilers of some standard (but only return), is this also a behaviour true for other functions as well or is this implementation defined? It seems just out of the ordinary, my compiler is just a slightly outdated GCC port (MinGW).

推荐答案

K＆安培; R风格的函数声明：

K&R-style function declaration:

void foo(n) 
    int n; 
{

}

如果没有指定类型，则默认为int。这是有效的C89，C99没有

If type isn't specified, it defaults to int. This is valid in C89, not C99

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