| Message ID | 1366406262.9609.123.camel@gandalf.local.home (mailing list archive) |
|---|---|
| State | New, archived |
| Delegated to: | Bjorn Helgaas |
| Headers | show |
On Fri, Apr 19, 2013 at 3:17 PM, Steven Rostedt <rostedt@goodmis.org> wrote: > Does this fix your issue? Yep, that fixes the warning for me. Thanks! Bjorn > From d2802d0739dcc61af5e5ea00773ce7ddead4e9c2 Mon Sep 17 00:00:00 2001 > From: "Steven Rostedt (Red Hat)" <rostedt@goodmis.org> > 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 <bhelgaas@google.com> > Reported-by: Gary Hade <garyhade@us.ibm.com> > Signed-off-by: Steven Rostedt <rostedt@goodmis.org> > --- > 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 > > > -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Fri, Apr 19, 2013 at 04:30:14PM -0600, Bjorn Helgaas wrote: > On Fri, Apr 19, 2013 at 3:17 PM, Steven Rostedt <rostedt@goodmis.org> wrote: > > Does this fix your issue? > > Yep, that fixes the warning for me. Thanks! > > Bjorn It also worked for me. It got rid of every one the 1401 is_signed_type associated "warning: comparison of unsigned expression < 0 is always false" occurrences (during 3.9-rc7 `make W=1` kernel build) mentioned in my previous email. Gary > > > From d2802d0739dcc61af5e5ea00773ce7ddead4e9c2 Mon Sep 17 00:00:00 2001 > > From: "Steven Rostedt (Red Hat)" <rostedt@goodmis.org> > > 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 <bhelgaas@google.com> > > Reported-by: Gary Hade <garyhade@us.ibm.com> > > Signed-off-by: Steven Rostedt <rostedt@goodmis.org> > > --- > > 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 > > > > > > > -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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);