xcode 没有以前的原型？
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No previous prototype?
提问by Stas Jaro
Possible Duplicate:
Error: No previous prototype for function. Why am I getting this error?
可能的重复：
错误：没有以前的函数原型。为什么我收到这个错误？
I have a function that I prototyped in the header file, however Xcode still gives me warning No previous prototype for the function 'printBind'. I have the function setBindprototyped in the same way but I do not get an warning for this function in my implementation.
我有一个在头文件中原型化的函数，但是 Xcode 仍然给我警告No previous prototype for the function 'printBind'。我setBind以相同的方式对函数进行了原型设计，但在我的实现中没有收到有关此函数的警告。
CelGL.h
细胞生长素
#ifndef Under_Siege_CelGL_h
#define Under_Siege_CelGL_h
void setBind(int input);
void printBind();
#endif
CelGL.c
CelGL.c
#include <stdio.h>
#include "CelGL.h"
int bind;
void setBind(int bindin) { // No warning here?
bind = bindin;
}
void printBind() { // Warning here
printf("%i", bind);
}
回答by Jonathan Leffler
In C, this:
在 C 中，这个：
void printBind();
is not a prototype. It declares a function that returns nothing (void) but takes an indeterminate list of arguments. (However, that list of arguments is not variable; all functions taking a variable length argument list musthave a full prototype in scope to avoid undefined behaviour.)
不是原型。它声明了void一个不返回任何内容 ( ) 但接受不确定参数列表的函数。（但是，该参数列表不是可变的；所有采用可变长度参数列表的函数都必须在范围内具有完整的原型，以避免未定义的行为。）
void printBind(void);
That's a prototype for the function that takes no arguments.
这是不带参数的函数的原型。
The rules in C++ are different - the first declares a function with no arguments and is equivalent to the second.
C++ 中的规则是不同的——第一个声明一个没有参数的函数，等价于第二个。
The reason for the difference is historical (read 'dates back to the mid-1980s'). When prototypes were introduced into C (some years after they were added to C++), there was an enormous legacy of code that declared functions with no argument list (because that wasn't an option before prototypes were added), so backwards compatibility considerations meant that SomeType *SomeFunction();had to continue meaning 'a function that returns a SomeType *but for which we know nothing about the argument list'. C++ eventually added the SomeType *SomeFunction(void);notation for compatibility with C, but didn't need it since type-safe linkage was added early and all functions needed a prototype in scope before they were defined or used.
差异的原因是历史性的（读作“可追溯到 1980 年代中期”）。当原型被引入 C 时（在它们被添加到 C++ 几年后），有大量的代码遗留了声明没有参数列表的函数（因为在添加原型之前这不是一个选项），所以向后兼容性考虑意味着那SomeType *SomeFunction();必须继续意味着“一个返回 aSomeType *但我们对参数列表一无所知的函数”。C++ 最终添加了SomeType *SomeFunction(void);与 C 兼容的符号，但并不需要它，因为早期添加了类型安全链接，并且所有函数在定义或使用之前都需要范围内的原型。
