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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>
This commit is contained in:
Steven Rostedt (Red Hat) 2013-04-19 17:10:27 -04:00 committed by Steven Rostedt
parent c192c8356c
commit d2802d0739
1 changed files with 1 additions and 1 deletions
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2
include/linux/ftrace_event.h
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@ -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);