在c中初始化结构数组

Question

我已经用三个项目和it is showing 2 为我初始化了一个结构数组！！！

#include <stdio.h>

typedef struct record {
    int value;
    char *name;
} record;

int main (void) {
    record list[] = { (1, "one"), (2, "two"), (3, "three") };
    int n = sizeof(list) / sizeof(record);

    printf("list's length: %i \n", n);
    return 0;
}

这里发生了什么？我疯了吗？

Answer 1

将初始化更改为：

record list[] = { {1, "one"}, {2, "two"}, {3, "three"} };
/*                ^        ^  ^        ^  ^          ^  */

您使用(...) 进行的初始化会产生类似于{"one", "two", "three"} 的效果并创建一个带有元素{ {(int)"one", "two"}, {(int)"three", (char *)0} } 的结构数组

comma operator 在 C 中从左到右计算表达式并丢弃除最后一个之外的所有表达式。这就是1、2和3被丢弃的原因。

Answer 2

您没有正确初始化list。 将初始化元素放入() 将使编译器将, 视为comma operator 而不是分隔符。

你的编译器应该给出这些警告

[Warning] left-hand operand of comma expression has no effect [-Wunused-value]
[Warning] missing braces around initializer [-Wmissing-braces]
[Warning] (near initialization for 'list[0]') [-Wmissing-braces]
[Warning] initialization makes integer from pointer without a cast [enabled by default]
[Warning] (near initialization for 'list[0].value') [enabled by default]
[Warning] left-hand operand of comma expression has no effect [-Wunused-value]
[Warning] left-hand operand of comma expression has no effect [-Wunused-value]
[Warning] initialization makes integer from pointer without a cast [enabled by default]
[Warning] (near initialization for 'list[1].value') [enabled by default]
[Warning] missing initializer for field 'name' of 'record' [-Wmissing-field-initializers]

初始化应该做为

 record list[] = { {1, "one"}, {2, "two"}, {3, "three"} };