From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752392Ab3AWS6N (ORCPT ); Wed, 23 Jan 2013 13:58:13 -0500 Received: from e7.ny.us.ibm.com ([32.97.182.137]:34390 "EHLO e7.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751028Ab3AWS6B (ORCPT ); Wed, 23 Jan 2013 13:58:01 -0500 Date: Wed, 23 Jan 2013 10:57:33 -0800 From: Sukadev Bhattiprolu To: Michael Ellerman Cc: Jiri Olsa , linuxppc-dev@ozlabs.org, Anton Blanchard , paulus@samba.org, linux-kernel@vger.kernel.org, acme@ghostprotocols.net, mingo Subject: Re: [PATCH] perf: Fix compile warnings in tests/attr.c Message-ID: <20130123185733.GA22906@us.ibm.com> References: <20130119013052.GA24693@us.ibm.com> <20130121135906.GD1995@krava.brq.redhat.com> <20130121213823.GA4774@us.ibm.com> <1358898333.29791.14.camel@concordia> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1358898333.29791.14.camel@concordia> X-Operating-System: Linux 2.0.32 on an i486 User-Agent: Mutt/1.5.20 (2009-06-14) X-Content-Scanned: Fidelis XPS MAILER x-cbid: 13012318-5806-0000-0000-00001EA86B84 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Michael Ellerman [michael@ellerman.id.au] wrote: | > | make: *** [tests/attr.o] Error 1 | > | | > | i386 compiles fine | > | > __u64 is 'unsigned long long' on x86 and PRIu64 is 'llu' which is fine. | > | > __u64 is 'unsigned long' on Power and PRIu64 is 'lu' which is again fine. | > | > But __u64 is 'unsigned long long' on x86_64, but PRIu64 is '%lu' bc __WORDSIZE | > is 64. | | | This is a bit of a mess, but let me see if I can help explain it. Yes it is :-) thanks for explaining it. | | The root of the problem is that you're mixing up the kernel type __u64, | with the userspace format specifier PRIu64. struct perf_event_attr is shared with user space and is using __u64. Should it use uint64_t instead ? | | PRIu64 is the format specifier for printing a uint64_t, it _may_ also be | the right specifier for a __u64, but there's no guarantee of that - as | you have discovered. | | Inside the kernel both x86 and powerpc use unsigned long long always, in | 32-bit and 64-bit code. That means in the kernel we can always use %llu. | | On x86 that definition is also exported to userspace, so on x86 __u64 is | always unsigned long long. As you noticed this potentially differs from | uint64_t, which can be confusing. However it means in x86 userspace code | you can always print a __u64 with %llu. | | On powerpc we default to using definitions that match userspace, so | __u64 changes depending on your wordsize, and so you must use PRIu64 | etc. to print them. Well, using __u64 and PRIu64 seems breaks x86-64... | | There is however support in recent powerpc kernels to switch to using | unsigned long long even on 64-bit. See commit 2c9c6ce. | | You need to define __SANE_USERSPACE_TYPES__ before including types.h. | Then you can always use %llu to print __u64. but __SANE_USERSPACE_TYPES__ with __u64 and %llu seems to work on x86, x86-64, powerpc. Will modify my patch to add __SANE_USERSPACE_TYPES__ but leave the %llu as is. Sukadev