tavianator wrote:
> I mean it would be useful to round up to the alignment for when you wanne
> have an array of the structs, but I'm not sure this is actually required by
> the standard. Do you have more justification for the alignment requirement on
> structs containing FAMs?
Here's an example:
```c
struct S {
int foo;
char fam[];
};
struct S *s = malloc(9);
s->fam[4];
```
[Your C standard
quote](https://github.com/llvm/llvm-project/pull/111015#issuecomment-2392534292)
says
> when a . (or ->) operator has a left operand that is (a pointer to) a
> structure with a flexible array member and the right operand names that
> member, it behaves as if that member were replaced with the longest array
> (with the same element type) that would not make the structure larger than
> the object being accessed
which I interpret as the largest N such that `sizeof(struct S) <= 9` in
```
struct S {
int foo;
char fam[N];
};
```
Well, for N = 4 we have `sizeof(struct S) == 8` and for N = 5 we have
`sizeof(struct S) == 12` (due to alignment padding), therefore N = 4. That
makes `s->fam[4]` out-of-bounds. Am I wrong?
https://github.com/llvm/llvm-project/pull/112636
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