linux-kernel - Re: [PATCH] KEYS: trusted: fix -Wvarags warning

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Message-ID: <80837c90-0425-aadd-38d7-c3c866d29a0a@gmail.com>
Date:   Fri, 12 Oct 2018 12:27:00 -0500
From:   Denis Kenzior <denkenz@...il.com>
To:     Nick Desaulniers <ndesaulniers@...gle.com>
Cc:     jejb@...ux.ibm.com, dhowells@...hat.com,
        Nathan Chancellor <natechancellor@...il.com>,
        Eric Biggers <ebiggers@...gle.com>, zohar@...ux.vnet.ibm.com,
        jmorris@...ei.org, serge@...lyn.com,
        linux-integrity@...r.kernel.org, keyrings@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] KEYS: trusted: fix -Wvarags warning

Hi Nick,

>> So maybe I'm misunderstanding something, but the issue seems to be that
>> unsigned char is promoted to 'unsigned char *' by Clang and probably
>> unsigned int or int by gcc.
> 
> No. This is extremely well defined behavior in C.  In C, integral
> types are NEVER promoted to pointer to integer types, only to larger
> integral types through rules more complicated than the correct flags
> to pass to `tar`.
> https://xkcd.com/1168/
> 

Ah right.  Thanks for the correction.  So looks like bool won't work for 
the same reasons.  But unsigned int should work right?  But then again 
this is a boolean value and if we want to be paranoid we can simply 
tweak the 'c = h3' assignment to be something like:

c = !!h3;

So in the end, I'm happy with int or unsigned int.

Regards,
-Denis