From: Richard Fitzgerald <rf@opensource.cirrus.com>
To: <pmladek@suse.com>, <rostedt@goodmis.org>,
<sergey.senozhatsky@gmail.com>,
<andriy.shevchenko@linux.intel.com>, <linux@rasmusvillemoes.dk>,
<w@1wt.eu>, <davem@davemloft.net>, <kuba@kernel.org>
Cc: <netdev@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
<patches@opensource.cirrus.com>,
Richard Fitzgerald <rf@opensource.cirrus.com>
Subject: [PATCH v2 1/2] lib: test_scanf: Remove pointless use of type_min() with unsigned types
Date: Tue, 25 May 2021 12:05:45 +0100 [thread overview]
Message-ID: <20210525110546.6223-2-rf@opensource.cirrus.com> (raw)
In-Reply-To: <20210525110546.6223-1-rf@opensource.cirrus.com>
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@intel.com>
Signed-off-by: Richard Fitzgerald <rf@opensource.cirrus.com>
---
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
next prev parent reply other threads:[~2021-05-25 11:07 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-25 11:05 [PATCH v2 0/2] Fix truncation warnings from building test_scanf.c Richard Fitzgerald
2021-05-25 11:05 ` Richard Fitzgerald [this message]
-- strict thread matches above, loose matches on Subject: below --
2021-05-25 12:20 Richard Fitzgerald
2021-05-25 12:20 ` [PATCH v2 1/2] lib: test_scanf: Remove pointless use of type_min() with unsigned types Richard Fitzgerald
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