Re: [RFC] btrfs-progs: Support for musl libc (and perhaps also uclibc)

[Merlijn Wajer <merlijn@wizzup.org>]

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Hi,

On 17/12/14 17:49, David Sterba wrote:
> On Sat, Dec 13, 2014 at 03:35:09PM +0100, Merlijn Wajer wrote:
> [snip]
> 
>> Attached are the two patches generated with git format-patch. I am aware
>> that this may not be required format for submitting patches -- but
>> please give me some time to get used to the etiquette. :-)
> 
> Thanks, there are minor things that I won't bother to point out to
> occasional contributors and fix them myself. The only formal requirement
> is the Signed-off-by tag, you can find the description eg. here
> 
> http://lxr.free-electrons.com/source/Documentation/SubmittingPatches#L358

Alright, cool. I've rebased my two patches and used --signoff when
amending the commit. Please find the new patches attached.


>> Please let me know if musl-libc (or any other libc) is a supported
>> platform, and if so, if and how I can improve on said patches.
> 
> I'm not aware of non-glibc users, but I don't see any problem to add
> support for more libc implementations. However, I won't regularly verify
> that it builds so it might break.

That is fine; at this point there are not a lot of people using an
alternative libc, so this is common practice. I'll be here with a new
round of patches if it breaks in a future release; it shouldn't really
break too often. :)


> Seems that only standardized library calls are used in btrfs-progs so
> any kind of support is probably going to be satisfied by #ifdefs.
> Your patches are simple so I'll try to schedule them to some 3.18.x
> update.

That would be great; thank you.

Regards,
Merlijn

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From 0109fd7ce62eee8b16aa5bdf78f3de54011e00f3 Mon Sep 17 00:00:00 2001
From: Merlijn Wajer <merlijn@wizzup.org>
Date: Sat, 13 Dec 2014 15:07:25 +0100
Subject: [PATCH 1/2] Include headers required for musl-libc.

This fixes various compilation errors where PATH_MAX and XATTR_SIZE_MAX
were missing. To my knowledge, this should have no bad side effects.

Signed-off-by: Merlijn Wajer <merlijn@wizzup.org>
---
 btrfs-convert.c | 1 +
 help.c          | 1 +
 mkfs.c          | 2 ++
 3 files changed, 4 insertions(+)

diff --git a/btrfs-convert.c b/btrfs-convert.c
index 02c5e94..7b69a13 100644
--- a/btrfs-convert.c
+++ b/btrfs-convert.c
@@ -31,6 +31,7 @@
 #include <fcntl.h>
 #include <unistd.h>
 #include <uuid/uuid.h>
+#include <linux/limits.h>
 
 #include "ctree.h"
 #include "disk-io.h"
diff --git a/help.c b/help.c
index fab942b..56aaf9c 100644
--- a/help.c
+++ b/help.c
@@ -17,6 +17,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <limits.h>
 
 #include "commands.h"
 #include "utils.h"
diff --git a/mkfs.c b/mkfs.c
index e10e62d..6343831 100644
--- a/mkfs.c
+++ b/mkfs.c
@@ -35,6 +35,8 @@
 #include <uuid/uuid.h>
 #include <ctype.h>
 #include <sys/xattr.h>
+#include <limits.h>
+#include <linux/limits.h>
 #include <blkid/blkid.h>
 #include <ftw.h>
 #include "ctree.h"
-- 
2.0.4


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From 5ae5cfa3af473625ef5b31daf5f229f12be753d2 Mon Sep 17 00:00:00 2001
From: Merlijn Wajer <merlijn@wizzup.org>
Date: Sat, 13 Dec 2014 15:08:43 +0100
Subject: [PATCH 2/2] Disable backtrace and define __always_inline

Disable backtrace and define __always_inline when glibc is not used as
libc. This, together with some header changes allows btrfs-progs to
compile with musl-libc.

Signed-off-by: Merlijn Wajer <merlijn@wizzup.org>
---
 kerncompat.h | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/kerncompat.h b/kerncompat.h
index 8afadc8..05823a7 100644
--- a/kerncompat.h
+++ b/kerncompat.h
@@ -29,6 +29,12 @@
 #include <stddef.h>
 #include <linux/types.h>
 #include <stdint.h>
+
+#ifndef __glibc__
+#define BTRFS_DISABLE_BACKTRACE
+#define __always_inline __inline __attribute__ ((__always_inline__))
+#endif
+
 #ifndef BTRFS_DISABLE_BACKTRACE
 #include <execinfo.h>
 #endif
-- 
2.0.4


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