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:
Link: https://lore.kernel.org/lkml/CAHk-=wgoxnmsj8GEVFJSvTwdnWm8wVJthefNk2n6+4TC=20e0Q@mail.gmail.com/
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 <[email protected]>
---
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
On Fri, Sep 06, 2019 at 02:11:51PM -0700, Joe Perches wrote:
> 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:
> Link: https://lore.kernel.org/lkml/CAHk-=wgoxnmsj8GEVFJSvTwdnWm8wVJthefNk2n6+4TC=20e0Q@mail.gmail.com/
>
> 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.
Yeah, makes sense. Sorry for adding these in the first place.
Reviewed-by: Louis Taylor <[email protected]>
On Sat, Sep 7, 2019 at 9:15 PM Joe Perches <[email protected]> wrote:
>
> 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:
> Link: https://lore.kernel.org/lkml/CAHk-=wgoxnmsj8GEVFJSvTwdnWm8wVJthefNk2n6+4TC=20e0Q@mail.gmail.com/
>
> 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.
> - char %hhd or %hhx
> - short int %hd or %hx
> + char %d or %x
> + short int %d or %x
> + s8 %d or %x
> + s16 %d or %x
This is incorrect. Integral promotions promotes also sign, which will
produce too many f:s.
--
With Best Regards,
Andy Shevchenko
On Fri, 06 Sep 2019, Joe Perches <[email protected]> wrote:
> Link: https://lore.kernel.org/lkml/CAHk-=wgoxnmsj8GEVFJSvTwdnWm8wVJthefNk2n6+4TC=20e0Q@mail.gmail.com/
I thought Link: was for referencing the patch on the mailing list that
became the commit in git.
BR,
Jani.
--
Jani Nikula, Intel Open Source Graphics Center
On Fri, 06 Sep 2019 14:11:51 -0700
Joe Perches <[email protected]> wrote:
> 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:
> Link: https://lore.kernel.org/lkml/CAHk-=wgoxnmsj8GEVFJSvTwdnWm8wVJthefNk2n6+4TC=20e0Q@mail.gmail.com/
>
> 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 <[email protected]>
Applied, thanks.
I took the liberty of removing "Link:" (but not the URL) from the commit
message. That wasn't a patch tag, there is no real reason to make it
look like one...
jon