英文:
gcc no error with extra comma in array initializer
问题
这里是一个示例：
int main()
{
int a[] = {1, 2, 3,};
}
请注意在 3 后面有额外的 ,。即使使用 -Wall 选项编译也没有警告。我在阅读一些 coreutils 代码时注意到数组的最后一个元素后面似乎有逗号。这是未定义行为 (UB) 吗，还是实现定义的，或者就这样没问题？
英文:
Here's an example:
int main ()
{
int a[] = {1, 2, 3,};
}
Note the extra , after 3. There is no warning even with -Wall and everything. I noticed this while reading some coreutils code that seemed to have a comma after the last element of an array. Is this UB, implementation-defined, or fine as is?
答案1
得分: 5
根据C（和C++）语法，这样的初始化是正确的。
根据C标准
6.7.9 初始化
语法
1 初始化器：
赋值表达式
{ 初始化器列表 }
{ 初始化器列表， }
//...
你可以初始化标量对象，例如
int x = { 10, };
请注意，在C23中，您可以使用空大括号初始化对象（包括可变长度数组），例如
int x = {};
或
int n = 4;
int a[n] = {};
英文:
According to the C (and C++) grammar such an initialization is correct.
From the C Standard
> 6.7.9 Initialization
> Syntax
1 initializer:
assignment-expression
{ initializer-list }
{ initializer-list , }
//...
You may initialize such a way even scalar objects as for example
int x = { 10, };
Pay attention to that in C23 you may initialize objects (including variable length arrays) with empty braces as for example
int x = {};
or
int n = 4;
int a[n] = {};
答案2
得分: 2
代码部分不要翻译。以下是翻译好的部分：
"Fine as is. The C standard permits it."
（保持原样。C标准允许这样做。）
英文:
Fine as is. The C standard permits it.
答案3
得分: 0
不仅适用于声明，也适用于更改，您可以将；替换为,（以下示例中的结构体中的最后三行）：
typedef struct {
int a;
int b;
char c;
} test;
int main(void)
{
test hi = (test) {
.a = 0,
.b = 1,
.c = 'a',
};
hi.a = 6,
hi.b = 9,
hi.c = 'r';
}
英文:
Not only for declarations but also for changes, you can replace ; with , (struct in the example below) last three lines:
typedef struct {
int a;
int b;
char c;
} test;
int main(void)
{
test hi = (test) {
.a = 0,
.b = 1,
.c = 'a',
};
hi.a = 6,
hi.b = 9,
hi.c = 'r';
}
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