c - 两个结构体初始化的区别

Question

Struct的以下两个初始化有什么区别？ ?

Car ford = {
    .name = "Ford F-150",
    .price = 25000
};

和:

Car dodge = (Car) {
    .name = "Ram",
    .price = 1000
};

来自 Compiler Explorer ，看起来两者产生相同的代码:

(StructName)有什么用在结构之前做什么？在进行复杂的初始化时似乎有必要，例如:

CarPtr mazda = & (Car) {
    .name = "Mazda",
    .price = 20000
};

同样与 Possible to initialize/assign a struct pointer? 中的两个答案有关.

Answer 1

在本声明中

Car dodge = (Car) {
    .name = "Ram",
    .price = 1000
};

创建了两个 Car 类型的对象。第一个是未命名的复合字面量

(Car) {
    .name = "Ram",
    .price = 1000
}

用于初始化另一个命名对象闪避。
来自 C 标准(6.5.2.5 复合文字)

3 A postfix expression that consists of a parenthesized type namefollowed by a braceenclosed list of initializers is a compoundliteral. It provides an unnamed object whose value is given by theinitializer list.

实际上它类似于以下声明

Car ford = {
    .name = "Ford F-150",
    .price = 25000
};

Car dodge = ford;

不同之处在于，在上一个示例中，我们又创建了一个命名对象。
来自 C 标准(6.7.9 初始化)

13 The initializer for a structure or union object that has automaticstorage duration shall be either an initializer list as describedbelow, or a single expression that has compatible structure or uniontype. In the latter case, the initial value of the object, includingunnamed members, is that of the expression.