[libvirt] [PATCH] build: avoid compile failure on linux kernels older than 2.6.19

[Jim Meyering]

Daniel P. Berrange wrote:
> On Mon, May 17, 2010 at 04:25:43PM +0200, Jim Meyering wrote:
>> This is required for any kernel prior to 2.6.19,
>> since <linux/magic.h> didn't exist back then.
>> Now that file is provided by the kernel-headers package.
>>
>> >From d14ef1669968ffeb65076b007e318934ed99aa61 Mon Sep 17 00:00:00 2001
>> From: Jim Meyering <meyering at redhat.com>
>> Date: Mon, 17 May 2010 16:17:08 +0200
>> Subject: [PATCH] build: avoid compile failure on linux kernels older than 2.6.19
>>
>> * configure.ac: Check for <linux/magic.h>.
>> * src/util/storage_file.c: Include <linux/magic.h> only if present.
>> Linux kernels prior to 2.6.19 lacked it.
>> [__linux__] (NFS_SUPER_MAGIC): Define if not already defined.
>> ---
>>  configure.ac            |    2 +-
>>  src/util/storage_file.c |    7 ++++++-
>>  2 files changed, 7 insertions(+), 2 deletions(-)
>>
>> diff --git a/configure.ac b/configure.ac
>> index c187420..ebd2082 100644
>> --- a/configure.ac
>> +++ b/configure.ac
>> @@ -108,7 +108,7 @@ LIBS=$old_libs
>>
>>  dnl Availability of various common headers (non-fatal if missing).
>>  AC_CHECK_HEADERS([pwd.h paths.h regex.h sys/syslimits.h \
>> -  termios.h sys/poll.h syslog.h mntent.h net/ethernet.h])
>> +  termios.h sys/poll.h syslog.h mntent.h net/ethernet.h linux/magic.h])
>>
>>  dnl Where are the XDR functions?
>>  dnl If portablexdr is installed, prefer that.
>> diff --git a/src/util/storage_file.c b/src/util/storage_file.c
>> index 5f15a64..a07bedc 100644
>> --- a/src/util/storage_file.c
>> +++ b/src/util/storage_file.c
>> @@ -27,7 +27,9 @@
>>  #include <unistd.h>
>>  #include <fcntl.h>
>>  #ifdef __linux__
>> -# include <linux/magic.h>
>> +# if HAVE_LINUX_MAGIC_H
>> +#  include <linux/magic.h>
>> +# endif
>
> Don't bother with this - just kill this include off completely. It is a
> waste of time using it if we can't rely on it existing & have to re-define
> everything ourselves.

I admit that those numbers will probably never change, but I see
including the recommended/modern header as the preferred approach.
Then, eventually when the old systems are no longer relevant (yeah, in
a long time) we'll be able to remove our hackish define-if-required code.