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To: Thomas Monjalon <thomas@monjalon.net>, dev@dpdk.org
References: <20210209152643.1832506-1-ferruh.yigit@intel.com>
 <20210519192449.2688051-1-thomas@monjalon.net>
From: Ferruh Yigit <ferruh.yigit@intel.com>
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Date: Fri, 21 May 2021 13:01:57 +0100
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Subject: Re: [dpdk-dev] [PATCH v2] devtools: check %l format specifier
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On 5/19/2021 8:24 PM, Thomas Monjalon wrote:
> From: Ferruh Yigit <ferruh.yigit@intel.com>
> 
> %lx or %llx tend to be wrong for 32-bit platform
> if used for fixed size variable like uint64_t.
> A checkpatch warning will avoid this common mistake.
> 
> Signed-off-by: Ferruh Yigit <ferruh.yigit@intel.com>
> Signed-off-by: Thomas Monjalon <thomas@monjalon.net>
> ---
> v2: proposal to reword the message and comment
> ---
>  devtools/checkpatches.sh | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/devtools/checkpatches.sh b/devtools/checkpatches.sh
> index db4c7d8301..0e09b2cab8 100755
> --- a/devtools/checkpatches.sh
> +++ b/devtools/checkpatches.sh
> @@ -69,6 +69,14 @@ check_forbidden_additions() { # <patch>
>  		-f $(dirname $(readlink -f $0))/check-forbidden-tokens.awk \
>  		"$1" || res=1
>  
> +	# check %l or %ll format specifier
> +	awk -v FOLDERS='lib drivers app examples' \
> +		-v EXPRESSIONS='%ll*[xud]' \
> +		-v RET_ON_FAIL=1 \
> +		-v MESSAGE='Using %l format, should it be %PRI*64?' \
> +		-f $(dirname $(readlink -f $0))/check-forbidden-tokens.awk \
> +		"$1" || res=1
> +
>  	# forbid variable declaration inside "for" loop
>  	awk -v FOLDERS='.' \
>  		-v EXPRESSIONS='for[[:space:]]*\\((char|u?int|unsigned|s?size_t)' \
> 

Using the %l or %ll format specifier is correct when the variable type is "long
int" or "long long int", it is only wrong if the variable type is fixed size
like 'unit64_t'.

My concern is above warning log may cause people change the correct usage.

That was why I tried to make wording less strict, more like a reminder to double
check the usage.

If we can check that format specifier is used for 'unit64_t' variable, that will
be the best solution but that is very hard to do.
Should we add a little more information to the message to prevent false hit on
the correct usage?