编译器报错提示 此声明没有存储类或类型说明符 或 xx does not name a type
个人原因
因为我在头文件中运行了如下语句
struct EXAMPLE examples;
examples.input = "hello world"
但是 函数外只能定义全局变量或者对象 ，而不能执行语句及调用函数 。
可以改为
struct EXAMPLE examples = {.input = "hello world"};
但是注意C语言中结构体初始化时，对于内部元素的顺序没有要求，但是C++不一样。
因为C++结构体初始化时，必须按照定义的顺序进行初始化，不能够跳过其中内容而初始化其他选项，或者定义的顺序先后有问题。
否则会报错:sorry, unimplemented: non-trivial designated initializers not supported
c++最好这么写
struct EXAMPLE examples = {"hello world"};
原因2
i just had this problem, and like Arckaroph have said : the problem is that when we include
a header file in a source code file, and we use in it the directive #ifndef, we can't include
it again in a header file to give a type of it's included class to a variable in source code file
example :
class1.h contains Class1 class2.h contains Class2 class2 have a private variable V with
class1 type if we include class1.h in class2.CPP we can't include it in class2.h to give V a class1 type.
so we put in class2.cpp class2.h before class1.h or we delete class1.h from class2.cpp