On Tue, 18 Jan 2022, Bin.Cheng via Gcc-help wrote:
> Hi,
> With -Waddress-of-packed-member option, GCC gives warning message if
> address of packed structure member is taken and assigned to pointer,
> like:
> struct foo {
> char a;
> int b;
> } __attribute__((packed));
>
> int main()
> {
> struct foo foo;
> int *p;
> p = &foo.b; // !!
> *p = 1234;
> return 0;
> }
>
> This is expected, however, I wonder if there is any way to let gcc
> know that `p` is a pointer that might be unaligned, so that an
> unaligned access instruction is generated if `p` is dereferenced?
> IIRC, microsoft compiler has __unaligned keyword extended for pointer
> declaration.
Sure, just add a new type with non-standard alignment. Instead of
'int *p' you can write e.g.
typedef int i32u __attribute__((aligned(1)));
i32u *p;
Alexander
