如果 char 比 int 具有更严格的对齐要求，那么这个联合会起作用吗？
最近，我遇到了以下代码片段，它试图确保 i 的所有字节（仅此而已）都可以作为 c 的单个元素进行访问：
union {
int i;
char c[sizeof(int)];
};
现在这似乎是一个很好的选择想法，但我想知道标准是否允许 char 的对齐要求比 int 的对齐要求更严格的情况。
换句话说，是否有可能有一个四字节 int 需要在四字节边界上与一字节 char 对齐（根据定义，它是一个字节，请参见下文） ）需要在十六字节边界上对齐吗？
这会影响上面联合的使用吗？
有两件事需要注意。
我在这里具体谈论标准允许的内容，而不是健全的实现者/架构将提供的内容。
我我在 ISO C 意义上使用术语“字节”，它是
char的宽度，不一定是 8 位。
Recently I came across the following snippet, which is an attempt to ensure all bytes of i (nad no more) are accessible as individual elements of c:
union {
int i;
char c[sizeof(int)];
};
Now this seems a good idea, but I wonder if the standard allows for the case where the alignment requirements for char are more restrictive than that for int.
In other words, is it possible to have a four-byte int which is required to be aligned on a four-byte boundary with a one-byte char (it is one byte, by definition, see below) required to be aligned on a sixteen-byte boundary?
And would this stuff up the use of the union above?
Two things to note.
I'm talking specifically about what the standard allows here, not what a sane implementor/architecture would provide.
I'm using the term "byte" in the ISO C sense, where it's the width of a
char, not necessarily 8 bits.
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没有任何类型比其大小有更严格的对齐要求（因为数组的工作方式），并且
sizeof(char)为 1。如果不明显：
sizeof(T [N])是sizeof(T)*N。sizeof以char为单位；所有类型都表示为固定数量的字节 (char)，该数字就是它们的大小。详细信息请参见 6.2.6（类型的表示）。(char *)&A[1] - (char *)&A[0]等于sizeof A [0]。T的对齐要求不大于sizeof(T)（实际上它除以sizeof(T)）No type can ever have stricter alignment requirements than its size (because of how arrays work), and
sizeof(char)is 1.In case it's not obvious:
sizeof(T [N])issizeof(T)*N.sizeofis in units ofchar; all types are represented as a fixed number of bytes (char), that number being their size. See 6.2.6 (Representation of Types) for details.T A[2];,(char *)&A[1] - (char *)&A[0]is equal tosizeof A[0].Tis no greater thansizeof(T)(in fact it dividessizeof(T))看看此帖子。在那里，我对 C Unions 的实用性提出了质疑，并得到了一些有趣的见解。重要的是，该标准根本无法确保不同字段的一致性！
编辑：paxdiablo，刚刚注意到你是回答这个问题的人之一，所以你可能应该熟悉这个限制。
Have a look at this thread. There, I questioned the usefulness of C Unions and there are some interesting insights. The important thing is that the Standard does not ensure the alignment of the different fields at all!
EDIT: paxdiablo, just noticed you were one of the guys answering that question, so you should probably be familiar with this limitation.