From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from hrndva-omtalb.mail.rr.com ([71.74.56.122]:4239 "EHLO hrndva-omtalb.mail.rr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754382Ab3DSVRo (ORCPT ); Fri, 19 Apr 2013 17:17:44 -0400 Message-ID: <1366406262.9609.123.camel@gandalf.local.home> Subject: Re: "unsigned expression < 0" always false warning From: Steven Rostedt To: Bjorn Helgaas Cc: Frederic Weisbecker , Ingo Molnar , "linux-pci@vger.kernel.org" , Lance Ortiz , Gary Hade Date: Fri, 19 Apr 2013 17:17:42 -0400 In-Reply-To: References: Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Sender: linux-pci-owner@vger.kernel.org List-ID: Does this fix your issue? -- Steve >>From d2802d0739dcc61af5e5ea00773ce7ddead4e9c2 Mon Sep 17 00:00:00 2001 From: "Steven Rostedt (Red Hat)" Date: Fri, 19 Apr 2013 17:10:27 -0400 Subject: [PATCH] tracing: Compare to 1 instead of zero for is_signed_type() The formats of the trace events show if the type of a event field is signed or not via a macro called is_signed_type(). This does a trick with the type and compares a -1 to zero after typecasting to the tested type. If it returns true, it's signed, otherwise its not. But this unfortunately triggers a warning by gcc: warning: comparison of unsigned expression < 0 is always false As we know it is always false (that's why we do it), this is a false warning. Luckily for us, the comparison works with a 1 as well, without giving the warning. Convert the check to compare (type)-1 < (type)0 to (type)-1 < (type)1 to determine if the type is signed or not. Link: http://lkml.kernel.org/r/CAErSpo4YXcY9fuOKWYGDkddJwk68kmZTohsmVB6QvrhjboOh1Q@mail.gmail.com Reported-by: Bjorn Helgaas Reported-by: Gary Hade Signed-off-by: Steven Rostedt --- include/linux/ftrace_event.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/include/linux/ftrace_event.h b/include/linux/ftrace_event.h index 4e28b01..34e00fb 100644 --- a/include/linux/ftrace_event.h +++ b/include/linux/ftrace_event.h @@ -333,7 +333,7 @@ extern int trace_define_field(struct ftrace_event_call *call, const char *type, extern int trace_add_event_call(struct ftrace_event_call *call); extern void trace_remove_event_call(struct ftrace_event_call *call); -#define is_signed_type(type) (((type)(-1)) < (type)0) +#define is_signed_type(type) (((type)(-1)) < (type)1) int trace_set_clr_event(const char *system, const char *event, int set); -- 1.7.10.4