linux-kernel - Re: [PATCH] objtool: Be lenient about -Wundef

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Message-ID: <20190628000033.ipcypg4kny2whfz7@treble>
Date:   Thu, 27 Jun 2019 19:00:34 -0500
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Olof Johansson <olof@...om.net>
Cc:     Peter Zijlstra <peterz@...radead.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] objtool: Be lenient about -Wundef

On Wed, Jun 19, 2019 at 05:03:37AM -0700, Olof Johansson wrote:
> Some libelf versions use undefined macros, which combined with newer GCC
> makes for errors from system headers. This isn't overly useful to fail
> compiling objtool for.
> 
> Error as seen:
> 
> cc1: all warnings being treated as errors
> In file included from arch/x86/../../elf.h:10,
>                  from arch/x86/decode.c:14:
> /usr/include/libelf/gelf.h:25:5: error: "__LIBELF_INTERNAL__" is not defined, evaluates to 0 [-Werror=undef]
>  #if __LIBELF_INTERNAL__
>      ^~~~~~~~~~~~~~~~~~~
> 
> For this reason, skip -Wundef on objtool.
> 
> Signed-off-by: Olof Johansson <olof@...om.net>

Sorry for the delay, I was out last week and I'm still getting caught
up.

Which libelf was this?  I'm guessing it's the old non-elfutils version
which has been unmaintained for 10 years (and which doesn't work with
objtool anyway).

It would be nice if we could figure out a way to detect that libelf and
report a more useful error for it.

-- 
Josh