注意：C语言结构体里不能赋初始值！
创建结构体只是开辟了一块内存空间，而不赋初始值，赋初始值有的编译器不支持的!
啥时候能赋初始值呢，c++11
20230816
C语言结构体无法赋初始值的解析
在本文中，我们将详细讨论C语言结构体为何无法赋予初始值。这是一个比较基础但又至关重要的话题，因为理解此问题有助于深入理解C语言以及内存管理的工作方式。
一、C语言结构体概述
首先，我们需要理解C语言中的结构体（struct）。结构体是一种可以储存不同类型数据的复合数据类型1。例如：
struct student {
char name[50];
int roll;
float marks;
};
上面的代码定义了一个名为student的结构体，其中包含了三个不同类型的字段：一个字符数组name，一个整数roll和一个浮点数marks。
二、C语言结构体不能赋初始值的原因
在C语言中，我们不能直接在结构体定义时为其成员变量赋予初始值。以下是一个尝试为结构体成员赋初始值的例子：
struct student {
char name[50] = "John"; // 错误！
int roll = 100; // 错误！
float marks = 90.5; // 错误！
};
这段代码会引发编译错误，原因如下：
-
内存分配时间：C语言对于全局变量、静态变量和数组（数组长度在编译时已知），以及函数内部的局部变量，内存空间是在编译时分配的（指编译器计算出这些变量在内存中的偏移量，并在生成的可执行文件中保留这些信息），而非运行时。由于结构体可能被多次实例化，所以编译器不允许在定义结构体时为其成员变量赋初值2。
-
语法限制：C语言的语法规定，在定义数据类型时（包括结构体），只能指定数据类型，不能进行初始化3。
三、C语言结构体初始化方法
尽管不能在定义结构体时为其成员赋初始值，但我们可以在创建结构体变量时进行初始化。例如：
struct student s1 = {"John", 100, 90.5};
或者，我们也可以在创建结构体变量后，单独为每个成员赋值：
struct student s1;
strcpy(s1.name, "John");
s1.roll = 100;
s1.marks = 90.5;
四、总结
C语言中，由于内存分配时间和语法限制，结构体定义时无法为其成员变量赋初值。但在创建结构体变量时，我们可以通过列表初始化或单独赋值的方式来设定成员变量的值。
参考资料
ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ ᅟᅠ
“Structures in C.” GeeksforGeeks. ↩︎
“Why can’t we initialize members in the structure declaration?” StackOverflow. ↩︎
“C Programming/Structures.” Wikibooks. ↩︎