C语言 Xcode - 警告：函数的隐式声明在 C99 中无效
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Xcode - Warning: Implicit declaration of function is invalid in C99
提问by CodingUpStream
Getting a warning : Implicit declaration of function 'Fibonacci' is invalid in C99. What's wrong?
收到警告：函数 'Fibonacci' 的隐式声明在 C99 中无效。怎么了？
#include <stdio.h>
int main(int argc, const char * argv[])
{
int input;
printf("Please give me a number : ");
scanf("%d", &input);
getchar();
printf("The fibonacci number of %d is : %d", input, Fibonacci(input)); //!!!
}/* main */
int Fibonacci(int number)
{
if(number<=1){
return number;
}else{
int F = 0;
int VV = 0;
int V = 1;
for (int I=2; I<=getal; I++) {
F = VV+V;
VV = V;
V = F;
}
return F;
}
}/*Fibonacci*/
回答by eckes
The function has to be declared before it's getting called. This could be done in various ways:
该函数必须在被调用之前声明。这可以通过多种方式完成：
Write down the prototype in a header
Use this if the function shall be callable from several source files. Just write your prototypeint Fibonacci(int number);
down in a.hfile (e.g.myfunctions.h) and then#include "myfunctions.h"in the C code.Move the function before it's getting called the first time
This means, write down the functionint Fibonacci(int number){..}
before yourmain()functionExplicitly declare the function before it's getting called the first time
This is the combination of the above flavors: type the prototype of the function in the C file before yourmain()function
在头文件中写下原型
如果该函数可以从多个源文件中调用，请使用它。只需将您的原型写int Fibonacci(int number);
在一个.h文件中（例如myfunctions.h），然后#include "myfunctions.h"在 C 代码中。在第一次调用之前移动函数
这意味着，int Fibonacci(int number){..}
在你的函数之前写下main()函数显式声明的功能，它变得首次调用之前
这是上面口味的组合：您之前键入C文件的函数的原型main()功能
As an additional note: if the function int Fibonacci(int number)shall only be used in the file where it's implemented, it shall be declared static, so that it's only visible in that translation unit.
作为附加说明：如果该函数int Fibonacci(int number)只能在实现它的文件中使用，则应声明static它，以便它仅在该翻译单元中可见。
回答by vikingosegundo
The compiler wants to know the function before it can use it
编译器想在使用函数之前知道它
just declare the function before you call it
只需在调用之前声明该函数
#include <stdio.h>
int Fibonacci(int number); //now the compiler knows, what the signature looks like. this is all it needs for now
int main(int argc, const char * argv[])
{
int input;
printf("Please give me a number : ");
scanf("%d", &input);
getchar();
printf("The fibonacci number of %d is : %d", input, Fibonacci(input)); //!!!
}/* main */
int Fibonacci(int number)
{
//…
回答by lee
I have the same warning (it's make my app cannot build). When I add C functionin Objective-C's .m file, But forgot to declared it at .hfile.
我有同样的警告（它使我的应用程序无法构建）。当我添加C function时Objective-C's .m file，但忘记在.h文件中声明它。
回答by QuaziRidwanHasib
should call the function properly; like- Fibonacci:input
应该正确调用函数；喜欢-斐波那契：输入
