[PATCH v3] trace_printk: remove local variable for argument detection

[Qian-Yu Lin]

The trace_printk() macro uses a local variable _______STR to detect
whether variadic arguments are present. This name can shadow outer
variables.

Replace the local variable with sizeof applied directly to the
stringified arguments:

  if (sizeof __stringify((__VA_ARGS__)) > 3)

This eliminates the shadowing risk entirely without introducing
any additional includes or local variables.

Verified with objdump on samples/trace_printk that all four cases
branch correctly: __trace_bputs, __trace_puts, __trace_bprintk,
and __trace_printk.

Suggested-by: David Laight <david.laight.linux@xxxxxxxxx>
Signed-off-by: Qian-Yu Lin <tiffany019230@xxxxxxxxx>
---
 include/linux/trace_printk.h | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/include/linux/trace_printk.h b/include/linux/trace_printk.h
index 2670ec7f4262..3d54f440dccf 100644
--- a/include/linux/trace_printk.h
+++ b/include/linux/trace_printk.h
@@ -86,8 +86,7 @@ do {									\
 
 #define trace_printk(fmt, ...)				\
 do {							\
-	char _______STR[] = __stringify((__VA_ARGS__));	\
-	if (sizeof(_______STR) > 3)			\
+	if (sizeof __stringify((__VA_ARGS__)) > 3)		\
 		do_trace_printk(fmt, ##__VA_ARGS__);	\
 	else						\
 		trace_puts(fmt);			\
-- 
2.43.0