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Subject: Re: linux-next: build failure after merge of the mac80211-next tree
From: Johannes Berg <johannes@sipsolutions.net>
To: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: linux-next@vger.kernel.org, linux-kernel@vger.kernel.org,
        Heikki Krogerus <heikki.krogerus@linux.intel.com>
Date: Wed, 24 Feb 2016 09:12:41 +0100
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References: <20160224115927.3fa9161e@canb.auug.org.au>
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Hi Stephen,

> [...]
> include/linux/bug.h:74:2: note: in expansion of macro
> 'BUILD_BUG_ON_MSG'
>   BUILD_BUG_ON_MSG(condition, "BUILD_BUG_ON failed: " #condition)
>   ^
> net/rfkill/core.c:647:2: note: in expansion of macro 'BUILD_BUG_ON'
>   BUILD_BUG_ON(!rfkill_types[NUM_RFKILL_TYPES - 1]);
>   ^
> 
> Caused by commit
> 
>   1f86443b4ffe ("net: rfkill: add rfkill_find_type function")

Thanks for the heads-up.

> Maybe the compiler version matters?  I am using gcc v5.2.0.

Hm. I'm using Debian 5.3.1-8.

> Though, it seems to be that "!rfkill_types[NUM_RFKILL_TYPES - 1]" is
> not a constant expression since
> 
> static const char *rfkill_types[NUM_RFKILL_TYPES]
> 
> does not stop "rfkill_types[NUM_RFKILL_TYPES - 1]" being modified at
> run time. I think that you might need:
> 
> static const char * const rfkill_types[NUM_RFKILL_TYPES]

That's true, but since I can't test it I'll just solve this
differently. We'll never be able to insert anything into the middle, so
we can also just BUILD_BUG_ON() the ARRAY_SIZE() and do the code a bit
differently.

Thanks,
johannes