I am okay to remove it.

Even it can be used to check the error types, but some of the developers do typecast on enum which makes the rule no sense.

/Ken

From: TF-M <tf-m-bounces@lists.trustedfirmware.org> On Behalf Of David Hu via TF-M
Sent: Friday, September 3, 2021 3:45 PM
To: tf-m@lists.trustedfirmware.org
Cc: nd <nd@arm.com>
Subject: [TF-M] [RFC] Can we remove the rule to use enum for error code?

Hi all,

Probably you didn’t know that there is such a rule in TF-M coding standard:

• Use enumeration for error codes to keep the code readable.

Personally, I’d prefer macros to enum, for error codes.

• The implicit type casting of enum can be an issue in coding. TF-M has a document to solve this.
• Using macros to define error codes aligns with PSA return code definitions.
• Enum makes function and variable definitions longer
• Enum may help developers skip writing specific error code values. But it becomes a trouble when you see an error number from log. You might need to count the enum fields one by one.
• Error codes for errors are usually negative but enums are positive ones by default.

I’d like to propose to remove this rule from TF-M coding standard.

But it doesn’t mean that enum shall not be used anymore.

I’m wondering if macros for error code in TF-M can be approved as well. 😊

May I know your opinions please?

If it is a convention or a good practice to use enum for error codes in security/trusted software, please help point me to the reference. I don’t find one via google. Thanks a lot!

Best regards,

Hu Ziji