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Re: [PATCH -tip 1/2] x86/alternatives: Fix build warning
- From: Masami Hiramatsu <mhiramat at redhat dot com>
- To: Ingo Molnar <mingo at elte dot hu>
- Cc: lkml <linux-kernel at vger dot kernel dot org>, systemtap <systemtap at sources dot redhat dot com>, DLE <dle-develop at lists dot sourceforge dot net>
- Date: Fri, 05 Feb 2010 11:52:37 -0500
- Subject: Re: [PATCH -tip 1/2] x86/alternatives: Fix build warning
- References: <20100205062427.3745.85746.stgit@dhcp-100-2-132.bos.redhat.com> <20100205071249.GB9320@elte.hu>
Ingo Molnar wrote:
>
> * Masami Hiramatsu <mhiramat@redhat.com> wrote:
>
>> Fixes below warnings.
>>
>> ====
>> FYI, there's this new build warning on x86 defconfig:
>>
>> arch/x86/kernel/alternative.c: In function 'alternatives_text_reserved':
>> arch/x86/kernel/alternative.c:402: warning: comparison of distinct pointer types lacks a cast
>> arch/x86/kernel/alternative.c:402: warning: comparison of distinct pointer types lacks a cast
>> arch/x86/kernel/alternative.c:405: warning: comparison of distinct pointer types lacks a cast
>> arch/x86/kernel/alternative.c:405: warning: comparison of distinct pointer types lacks a cast
>>
>> Caused by:
>>
>> 2cfa197: ftrace/alternatives: Introducing *_text_reserved functions
>> ====
>>
>> Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
>> Reported-by: Ingo Molnar <mingo@elte.hu>
>> ---
>>
>> arch/x86/kernel/alternative.c | 4 ++--
>> 1 files changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
>> index 3832fdc..99d9920 100644
>> --- a/arch/x86/kernel/alternative.c
>> +++ b/arch/x86/kernel/alternative.c
>> @@ -399,10 +399,10 @@ int alternatives_text_reserved(void *start, void *end)
>> u8 **ptr;
>>
>> list_for_each_entry(mod, &smp_alt_modules, next) {
>> - if (mod->text > end || mod->text_end < start)
>> + if (mod->text > (u8 *)end || mod->text_end < (u8 *)start)
>> continue;
>> for (ptr = mod->locks; ptr < mod->locks_end; ptr++)
>> - if (start <= *ptr && end >= *ptr)
>> + if ((u8 *)start <= *ptr && (u8 *)end >= *ptr)
>> return 1;
>> }
>
> Such casts are a bit ugly and in general type casts are somewhat dangerous.
I doubt this type casting is dangerous..., but yeah, it's ugly :-)
> One possible solution would be to add intermediary local variables
> (text_start/text_end) with u8 * type and assign start/end to them - which can
> be done without a cast.
Sure, I'll update it.
Thank you,
--
Masami Hiramatsu
Software Engineer
Hitachi Computer Products (America), Inc.
Software Solutions Division
e-mail: mhiramat@redhat.com