packed struct sizeof wrong

packed struct sizeof wrong

[Johannes Berg]

Hi all,

I ran across this in some of my kernel code, and isolated it into a few
test cases, below. sparse should not report errors on this file, but
does regardless, somehow the structs appear larger to it than they are.

johannes

This is suitable for dropping into the validation directory:
--- begin file ---
struct A {
	unsigned char a, b, c, d;
} __attribute__((packed));

struct B {
	struct A A;
	unsigned char e, f;
	unsigned short g;
	unsigned char h;
} __attribute__((packed));

struct C {
	unsigned char a, b, c, d;
	unsigned char e, f;
	unsigned short g;
	unsigned char h;
} __attribute__((packed));

struct D {
	unsigned char h;
} __attribute__((packed));

struct E {
	unsigned short g;
	unsigned char h;
} __attribute__((packed));

#define BUILD_BUG_ON(expr) ((void)(sizeof(struct { int:-!!(expr); })))

static inline void foo(void)
{
	BUILD_BUG_ON(sizeof(struct A) != 4);
	BUILD_BUG_ON(sizeof(struct B) != 9);
	BUILD_BUG_ON(sizeof(struct C) != 9);
	BUILD_BUG_ON(sizeof(struct D) != 1);
	BUILD_BUG_ON(sizeof(struct E) != 3);
}

/*
 * check-name: packed struct sizeof
 */