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SubjectRe: [RFC] Splitting out kernel<=>userspace ABI headers
On Sep 3, 2005, at 11:19:17, H. Peter Anvin wrote:
> Thus, an ABIzed <linux/abi/stat.h> or whatever it's called might
> export
> "struct __kabi_stat" and "struct __kabi_stat64" with the
> expectation that
> the caller would "#define __kabi_stat64 stat" if that is the
> version they
> want. A typedef isn't good enough for C, since you can't typedef
> struct
> tags.

Didn't you mean "#define stat __kabi_stat64"? Also, I can see that
pose other issues as well say my app does "struct stat stat;" Any error
messages would refer to a variable "__kabi_stat64" instead of the

A userspace program:
struct stat stat;
stat.invalid = 1;

Preprocesses into:
struct __kabi_stat64 __kabi_stat64;
__kabi_stat64.invalid = 1;

And gives an error something like this for that line, confusing the
Invalid member "invalid" for "__kabi_stat64"

As far as I can tell, this is not a solvable issue unless GCC can
come up
with a way to either:
typedef struct foo struct bar;
struct bar { unnamed struct foo; };
the former being much nicer. On the other hand, I think the following
should work, because the st_* names are within the C namespace and
be much easier to redefine, although misuse of one of those names might
be a bit more catastrophic for the user app.

struct stat {
struct __kabi_stat64 __stat64;
#define st_dev __stat64.st_dev
#define st_ino __stat64.st_ino

Then the userspace program could do this:
struct stat foo;
foo.st_ino = 0;

And it would be preprocessed into:
struct stat foo;foo.__stat64.st_ino = 0;

Kyle Moffett

Somone asked me why I work on this free (
software stuff and not get a real job. Charles Shultz had the best

"Why do musicians compose symphonies and poets write poems? They do
it because
life wouldn't have any meaning for them if they didn't. That's why I
cartoons. It's my life."
-- Charles Shultz

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