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From: Joe Perches <>
To: Jonathan Corbet <>
	linux-kernel <>,
	Louis Taylor <>
Subject: [PATCH] docs: printk-formats: Stop encouraging use of unnecessary %h[xudi] and %hh[xudi]
Date: Fri, 06 Sep 2019 14:11:51 -0700	[thread overview]
Message-ID: <> (raw)

Standard integer promotion is already done and %hx and %hhx is useless
so do not encourage the use of %hh[xudi] or %h[xudi].

As Linus said in:

It's a pointless warning, making for more complex code, and
making people remember esoteric printf format details that have no
reason for existing.

The "h" and "hh" things should never be used. The only reason for them
being used if if you have an "int", but you want to print it out as a
"char" (and honestly, that is a really bad reason, you'd be better off
just using a proper cast to make the code more obvious).

So if what you have a "char" (or unsigned char) you should always just
print it out as an "int", knowing that the compiler already did the
proper type conversion.

Signed-off-by: Joe Perches <>
 Documentation/core-api/printk-formats.rst | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/Documentation/core-api/printk-formats.rst b/Documentation/core-api/printk-formats.rst
index c6224d039bcb..ecbebf4ca8e7 100644
--- a/Documentation/core-api/printk-formats.rst
+++ b/Documentation/core-api/printk-formats.rst
@@ -13,10 +13,10 @@ Integer types
 	If variable is of Type,		use printk format specifier:
-		char			%hhd or %hhx
-		unsigned char		%hhu or %hhx
-		short int		%hd or %hx
-		unsigned short int	%hu or %hx
+		char			%d or %x
+		unsigned char		%u or %x
+		short int		%d or %x
+		unsigned short int	%u or %x
 		int			%d or %x
 		unsigned int		%u or %x
 		long			%ld or %lx
@@ -25,10 +25,10 @@ Integer types
 		unsigned long long	%llu or %llx
 		size_t			%zu or %zx
 		ssize_t			%zd or %zx
-		s8			%hhd or %hhx
-		u8			%hhu or %hhx
-		s16			%hd or %hx
-		u16			%hu or %hx
+		s8			%d or %x
+		u8			%u or %x
+		s16			%d or %x
+		u16			%u or %x
 		s32			%d or %x
 		u32			%u or %x
 		s64			%lld or %llx

             reply	other threads:[~2019-09-06 21:11 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-06 21:11 Joe Perches [this message]
2019-09-06 21:37 ` Louis Taylor
2019-09-07 20:23 ` Andy Shevchenko
2019-09-09  9:36 ` Jani Nikula
2019-09-14  7:58 ` Jonathan Corbet

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