linux-kernel - Re: [RFC PATCH 12/13] blk-mq.h: Fix parentheses around macro parameter use

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Date:   Mon, 8 May 2023 10:28:58 -0400
From:   Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org, Jens Axboe <axboe@...nel.dk>,
        linux-block@...r.kernel.org
Subject: Re: [RFC PATCH 12/13] blk-mq.h: Fix parentheses around macro
 parameter use

I've attempted to capture the resulting rules based on our discussion to add this to
coding-style.rst. Please let me know if anything is wrong:

(to be added in section 12) Macros, Enums and RTL)

Always use parentheses around macro arguments, except when:

- they are used as a full expression:
   - as an initializer,
   - as an expression statement,
   - as the controlling expression of a selection statement (``if`` or ``switch``),
   - as the controlling expression of a ``while`` or ``do`` statement,
   - as any of the expressions of a ``for`` statement,
   - as the expression in a return statement,
- they are used as expression within an array subscript operator "[]",
- they are used as arguments to functions or other macros,
- there is some syntax reason why adding the parentheses would not work.

(note: I'm unsure about requiring or not the parentheses around initializers.
Based on C11 section "6.8 Statement and blocks", initializers that are not part of
a compound literal are full expressions, which makes the extra parentheses useless.)

Thanks,

Mathieu

-- 
Mathieu Desnoyers
EfficiOS Inc.
https://www.efficios.com