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Date: Thu, 13 Jun 2024 14:21:10 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Alexey Dobriyan <adobriyan@gmail.com>, linux-kernel@vger.kernel.org,
 linux-mm@kvack.org, linux-security-module@vger.kernel.org,
 linux-trace-kernel@vger.kernel.org
Subject: Re: [PATCH] linux++: delete some forward declarations
Message-Id: <20240613142110.30019a4084d922d63c6d4352@linux-foundation.org>
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On Thu, 13 Jun 2024 16:10:12 -0400 Steven Rostedt <rostedt@goodmis.org> wrote:

> > And...  I'm a bit surprised that forward declarations are allowed in C.
> > A billion years ago I used a C compiler which would use 16 bits for
> > an enum if the enumted values would fit in 16 bits.  And it would use 32
> > bits otherwise.  So the enumerated values were *required* for the
> > compiler to be able to figure out the sizeof.  But it was a billion
> > years ago.
> 
> Well, I only looked at the one change in ftrace.h which has a
> "struct seq_file;" that is not used anywhere else in the file, so that
> one definitely can go.

The risk is that something which includes ftrace.h is depending upon
the enum declaration.