[PATCH v2 1/2] lib: test_scanf: Remove pointless use of type_min() with unsigned types

From: Richard Fitzgerald
Date: Tue May 25 2021 - 07:07:48 EST


sparse was producing warnings of the form:

sparse: cast truncates bits from constant value (ffff0001 becomes 1)

There is no actual problem here. Using type_min() on an unsigned type
results in an (expected) truncation.

However, there is no need to test an unsigned value against type_min().
The minimum value of an unsigned is obviously 0, and any value cast to
an unsigned type is >= 0, so for unsigneds only type_max() need be tested.

This patch also takes the opportunity to clean up the implementation of
simple_numbers_loop() to use a common pattern for the positive and
negative test.

Reported-by: kernel test robot <lkp@xxxxxxxxx>
Signed-off-by: Richard Fitzgerald <rf@xxxxxxxxxxxxxxxxxxxxx>
---
lib/test_scanf.c | 13 ++++++-------
1 file changed, 6 insertions(+), 7 deletions(-)

diff --git a/lib/test_scanf.c b/lib/test_scanf.c
index 8d577aec6c28..48ff5747a4da 100644
--- a/lib/test_scanf.c
+++ b/lib/test_scanf.c
@@ -187,8 +187,8 @@ static const unsigned long long numbers[] __initconst = {
#define value_representable_in_type(T, val) \
(is_signed_type(T) \
? ((long long)(val) >= type_min(T)) && ((long long)(val) <= type_max(T)) \
- : ((unsigned long long)(val) >= type_min(T)) && \
- ((unsigned long long)(val) <= type_max(T)))
+ : ((unsigned long long)(val) <= type_max(T)))
+

#define test_one_number(T, gen_fmt, scan_fmt, val, fn) \
do { \
@@ -204,12 +204,11 @@ do { \
int i; \
\
for (i = 0; i < ARRAY_SIZE(numbers); i++) { \
- if (!value_representable_in_type(T, numbers[i])) \
- continue; \
+ if (value_representable_in_type(T, numbers[i])) \
+ test_one_number(T, gen_fmt, scan_fmt, \
+ numbers[i], fn); \
\
- test_one_number(T, gen_fmt, scan_fmt, numbers[i], fn); \
- \
- if (is_signed_type(T)) \
+ if (value_representable_in_type(T, -numbers[i])) \
test_one_number(T, gen_fmt, scan_fmt, \
-numbers[i], fn); \
} \
--
2.20.1