linux-kernel - Re: next-20190826 - objtool fails to build.

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Message-ID: <23345.1567020600@turing-police>
Date:   Wed, 28 Aug 2019 15:30:00 -0400
From:   "Valdis Klētnieks" <valdis.kletnieks@...edu>
To:     Josh Poimboeuf <jpoimboe@...hat.com>
Cc:     Peter Zijlstra <peterz@...radead.org>, linux-kernel@...r.kernel.org
Subject: Re: next-20190826 - objtool fails to build.

On Wed, 28 Aug 2019 10:10:04 -0500, Josh Poimboeuf said:

> But I don't see how those warnings could get enabled: -Wsign-compare
> -Wunused-parameter.
>
> Can you "make clean" and do "make V=1 tools/objtool" to show the actual
> flags?

And that tells me those warnings in fact don't get specifically enabled.
(I've added some line breaks for sanity)

  gcc -Wp,-MD,/usr/src/linux-next/tools/objtool/.special.o.d -Wp,-MT,/usr/src/linux-next/tools/objtool/special.o -O2 -D_FORTIFY_SOURCE=2 -Wall -Wextra -Wbad-function-cast

Found the cause of the mystery - I changed something in a bash profile, and
as a result...

export CFLAGS="-O2 -D_FORTIFY_SOURCE=2 -Wall -Wextra"

And -Wextra pulls in the things that cause problems. So this is mostly
self-inflicted.

The real question then becomes - should the Makefile sanitize CFLAGS or just
append to whatever the user supplied as it does currently? The rest of the tree
sanitizes CFLAG, because I don't get deluged in -Wsign-compare warnings all
over the place...

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