linux-kernel - [PATCH v2 1/3] lib/vsprintf: Replace hidden BUILD_BUG_ON() with static

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Message-Id: <20200731180825.30575-1-andriy.shevchenko@linux.intel.com>
Date:   Fri, 31 Jul 2020 21:08:22 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        linux-kernel@...r.kernel.org,
        Rasmus Villemoes <linux@...musvillemoes.dk>
Cc:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Steven Rostedt <rostedt@...dmis.org>
Subject: [PATCH v2 1/3] lib/vsprintf: Replace hidden BUILD_BUG_ON() with static_assert()

First of all, there is no compile time check for the SMALL
to be ' ' (0x20, i.e. space). Second, for ZEROPAD the check
is hidden in the code.

For better maintenance replace BUILD_BUG_ON() with static_assert()
for ZEROPAD and move it closer to the definition. While at it,
introduce check for SMALL.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Reviewed-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
---
v2: replaced to have plain defined constant on left side, added tag (Steven)
 lib/vsprintf.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 31a674dd2674..f90f09682977 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -381,6 +381,9 @@ int num_to_str(char *buf, int size, unsigned long long num, unsigned int width)
 #define SMALL	32		/* use lowercase in hex (must be 32 == 0x20) */
 #define SPECIAL	64		/* prefix hex with "0x", octal with "0" */
 
+static_assert(ZEROPAD == ('0' - ' '));
+static_assert(SMALL == ' ');
+
 enum format_type {
 	FORMAT_TYPE_NONE, /* Just a string part */
 	FORMAT_TYPE_WIDTH,
@@ -507,7 +510,7 @@ char *number(char *buf, char *end, unsigned long long num,
 	/* zero or space padding */
 	if (!(spec.flags & LEFT)) {
 		char c = ' ' + (spec.flags & ZEROPAD);
-		BUILD_BUG_ON(' ' + ZEROPAD != '0');
+
 		while (--field_width >= 0) {
 			if (buf < end)
 				*buf = c;
-- 
2.27.0