Messages in this thread Patch in this message | | | Date | Mon, 22 Apr 2013 11:20:27 -0400 | From | Steven Rostedt <> | Subject | [for-next][PATCH 1/2] tracing: Compare to 1 instead of zero for is_signed_type() |
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From: "Steven Rostedt (Red Hat)" <rostedt@goodmis.org>
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
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