[PATCH v2] devtools: allow variable declaration inside for loop

[Bruce Richardson]

On Wed, May 03, 2023 at 11:30:53AM +0100, Ferruh Yigit wrote:
> Declaring variable inside for loop is not supported via C89 and it was
> checked in checkpatch.sh via commit [1].
> But as DPDK supported C standard is becoming C99/C11 [2], declaring
> variable inside loop can be allowed.
> 
> [1]
> Commit 43e73483a4b8 ("devtools: forbid variable declaration inside for")
> 
> [2]
> https://dpdk.org/patch/121912
> 
> Signed-off-by: Ferruh Yigit <ferruh.yigit at amd.com>
> ---
> Cc: Bruce Richardson <bruce.richardson at intel.com>
> Cc: David Marchand <david.marchand at redhat.com>
> 
> v2:
>  * Update coding convention too
> ---

Acked-by: Bruce Richardson <bruce.richardson at intel.com>

>  devtools/checkpatches.sh                 | 8 --------
>  doc/guides/contributing/coding_style.rst | 1 +
>  2 files changed, 1 insertion(+), 8 deletions(-)
> 
> diff --git a/devtools/checkpatches.sh b/devtools/checkpatches.sh
> index 15d5d6709445..b5baf6f2b161 100755
> --- a/devtools/checkpatches.sh
> +++ b/devtools/checkpatches.sh
> @@ -78,14 +78,6 @@ check_forbidden_additions() { # <patch>
>  		-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)' \
> -		-v RET_ON_FAIL=1 \
> -		-v MESSAGE='Declaring a variable inside for()' \
> -		-f $(dirname $(readlink -f $0))/check-forbidden-tokens.awk \
> -		"$1" || res=1
> -
>  	# refrain from new additions of 16/32/64 bits rte_atomicNN_xxx()
>  	awk -v FOLDERS="lib drivers app examples" \
>  		-v EXPRESSIONS="rte_atomic[0-9][0-9]_.*\\\(" \
> diff --git a/doc/guides/contributing/coding_style.rst b/doc/guides/contributing/coding_style.rst
> index 89db6260cfbf..e18b8d4439ea 100644
> --- a/doc/guides/contributing/coding_style.rst
> +++ b/doc/guides/contributing/coding_style.rst
> @@ -558,6 +558,7 @@ Local Variables
>  
>  * Variables should be declared at the start of a block of code rather than in the middle.

I'd love to see this restriction removed in future too. Having a variable
declared on first use in the middle of block I find a far easier way of
working as a) it saves scrolling to look for variable definitions and b) it
makes it far easier when adding/removing blocks of code e.g. commenting out
for testing,  to have all the code together rather than having variables at
the top to add/remove also.

>    The exception to this is when the variable is ``const`` in which case the declaration must be at the point of first use/assignment.
> +  Declaring variable inside a for loop is OK.
>  * When declaring variables in functions, multiple variables per line are OK.
>    However, if multiple declarations would cause the line to exceed a reasonable line length, begin a new set of declarations on the next line rather than using a line continuation.
>  * Be careful to not obfuscate the code by initializing variables in the declarations, only the last variable on a line should be initialized.
> -- 
> 2.34.1
>