linux-ext4 - Re: e2fsprogs: How to get rid of the ext2

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Date:   Tue, 21 Aug 2018 11:47:21 -0400
From:   "Theodore Y. Ts'o" <tytso@....edu>
To:     Lukas Czerner <lczerner@...hat.com>
Cc:     linux-ext4@...r.kernel.org
Subject: Re: e2fsprogs: How to get rid of the ext2_types.h

On Tue, Aug 21, 2018 at 05:16:50PM +0200, Lukas Czerner wrote:
> The issue is in the header files ext2_types.h and blkid_types.h and
> those are going to differ depending on architecture. See:
> 
> ...
> #if (@SIZEOF_INT@ == 2)
> typedef        unsigned int    __u16;
> #else
> #if (@SIZEOF_SHORT@ == 2)
> typedef        unsigned short  __u16;
> ...

> > So this implies that on Fedora / RHEL either asm/types.h doesn't
> > exist, or it is not consistent on different platforms?
> 
> Not sure how did you come to this conclusion, but no asm/types.h is not
> the problem. On linux most of the blkid_types.h should really be
> irrelevant since we should be using linux/types.h, but we're not even
> consistent in that.

The reason why I suspect this is because we shouldn't be descending
into the "#if (@SIZEOF_INT@ == 2)" et. al. branches.  That's because we
*copy* the types from asm/types.h.  From /usr/include/ext2fs/ext2_types.h
on Debian:

#define __S8_TYPEDEF __signed__ char
#define __U8_TYPEDEF unsigned char
#define __S16_TYPEDEF __signed__ short
#define __U16_TYPEDEF unsigned short
#define __S32_TYPEDEF __signed__ int
#define __U32_TYPEDEF unsigned int
#define __S64_TYPEDEF __signed__ long long
#define __U64_TYPEDEF unsigned long long

This is done by the config/parse_types.sh script that I was talking
about.

#ifdef __U16_TYPEDEF
typedef __U16_TYPEDEF __u16;
#else
#if (4 == 2)
typedef	unsigned int	__u16;
#else
#if (2 == 2)
typedef	unsigned short	__u16;
	....

(Again, from Debian's /usr/include/ext2fs/ext2_fs.h)

So either (a) /usr/include/asm/types.h doesn't exist on Fedora (or
Fedora's build environment), or (b) /usr/include/asm/types.h must have
inconsistent types on i386 and x86_64.

No?

					- Ted

P.S.  blkid/types.h shouldn't be used at all, since these days blkid
comes from util-linux, not e2fsprogs.  I keep blkid in the tree for
the benefit of (a) NetBSD, and (b) Android, both of which don't use
util-linux.   So I'm confused why you are bringing up blkid/types.h?

P.P.S.  Since you are quoting "#if (@SIZEOF_INT@ == 2)" and not
"#if (4 == 2)" I'm guessing you're looking at ext2_types.h.in,
and not the actual generated file ext2_types.h.   So I guess there's
a 3rd possibility, (c) this really isn't a problem on RHEL / Fedora.