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From: Ed Maste <emaste@freebsd.org>
Date: Fri, 2 Jan 2015 09:41:13 -0500
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Subject: Re: asr(4) error with new clang/llvm
To: David Chisnall <theraven@freebsd.org>
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Cc: FreeBSD Current <freebsd-current@freebsd.org>,
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On 2 January 2015 at 04:07, David Chisnall <theraven@freebsd.org> wrote:
>
> The correct solution is to declare the array to have 0 elements (although=
 this will break C++ code).  A zero-length array at the end of a structure =
is specifically defined by the C standard (since C99) to be a variable-leng=
th array.  A length-one array was used in C89 prior to this for this purpos=
e.  Using a 1-element array in C is undefined behaviour.
>
> Note that this change will also require fixing code that allocates it to =
allocate space for n elements not n-1.

I was thinking of making that change, but the driver was not
particularly straightforward. In addition to your point about
allocation I noticed that it used sizeof() the union containing these
variable-length-array structs. I wouldn't want to try to fix it
without hardware to test.