linux-kernel - New sparse warning from min_t(): expression using sizeof(void)

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Date:   Sat, 21 Apr 2018 10:50:51 +0300
From:   Kalle Valo <kvalo@...eaurora.org>
To:     Kees Cook <keescook@...omium.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     luciano.coelho@...el.com, linux-kernel@...r.kernel.org,
        linux-wireless@...r.kernel.org
Subject: New sparse warning from min_t(): expression using sizeof(void)

Hi Kees&Linus,

after upgrading to v4.17-rc1 I started to see this sparse warning from
min_t():

drivers/net/wireless/ath/ath10k/wmi.c:4620:31: warning: expression using sizeof(void)

I counted 167 such warnings just from ath10k alone and Luca told me that
he sees similar sparse warnings with iwlwifi as well. My sparse is
pretty old (v0.5.0-44-g40791b94c56b) but Luca said updating sparse to
0.5.2 didn't help. I also see this with latest commit from Linus' tree
(83beed7b2b26).

After reverting these two commits the sparse warnings go away:

e9092d0d9796 Fix subtle macro variable shadowing in min_not_zero()
3c8ba0d61d04 kernel.h: Retain constant expression output for max()/min()

I had to revert e9092d0d9796 due to conflicts but it seems 3c8ba0d61d04
is the actual commit causing these warnings.

Is there any way to fix it? With ath10k I use sparse a lot and because
of these warnings sparse is now very annoying to use.

-- 
Kalle Valo