From: Masahiro Yamada <yamada.masahiro@socionext.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>,
Nick Desaulniers <ndesaulniers@google.com>,
Kees Cook <keescook@chromium.org>,
Josh Triplett <josh@joshtriplett.org>,
Masahiro Yamada <yamada.masahiro@socionext.com>,
linux-kernel@vger.kernel.org
Subject: [PATCH v4 2/3] build_bug.h: remove negative-array fallback for BUILD_BUG_ON()
Date: Thu, 22 Nov 2018 12:14:21 +0900 [thread overview]
Message-ID: <1542856462-18836-2-git-send-email-yamada.masahiro@socionext.com> (raw)
In-Reply-To: <1542856462-18836-1-git-send-email-yamada.masahiro@socionext.com>
The kernel can only be compiled with an optimization option (-O2, -Os,
or the currently proposed -Og). Hence, __OPTIMIZE__ is always defined
in the kernel source.
The fallback for the -O0 case is just hypothetical and pointless.
Moreover, commit 0bb95f80a38f ("Makefile: Globally enable VLA warning")
enabled -Wvla warning. The use of variable length arrays is banned.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>
---
Changes in v4: None
Changes in v3: None
Changes in v2: None
include/linux/build_bug.h | 14 --------------
1 file changed, 14 deletions(-)
diff --git a/include/linux/build_bug.h b/include/linux/build_bug.h
index 43d1fd5..d415c64 100644
--- a/include/linux/build_bug.h
+++ b/include/linux/build_bug.h
@@ -51,23 +51,9 @@
* If you have some code which relies on certain constants being equal, or
* some other compile-time-evaluated condition, you should use BUILD_BUG_ON to
* detect if someone changes it.
- *
- * The implementation uses gcc's reluctance to create a negative array, but gcc
- * (as of 4.4) only emits that error for obvious cases (e.g. not arguments to
- * inline functions). Luckily, in 4.3 they added the "error" function
- * attribute just for this type of case. Thus, we use a negative sized array
- * (should always create an error on gcc versions older than 4.4) and then call
- * an undefined function with the error attribute (should always create an
- * error on gcc 4.3 and later). If for some reason, neither creates a
- * compile-time error, we'll still have a link-time error, which is harder to
- * track down.
*/
-#ifndef __OPTIMIZE__
-#define BUILD_BUG_ON(condition) ((void)sizeof(char[1 - 2*!!(condition)]))
-#else
#define BUILD_BUG_ON(condition) \
BUILD_BUG_ON_MSG(condition, "BUILD_BUG_ON failed: " #condition)
-#endif
/**
* BUILD_BUG - break compile if used.
--
2.7.4
next prev parent reply other threads:[~2018-11-22 3:15 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-22 3:14 [PATCH v4 1/3] kernel.h: disable type-checks in container_of() for Sparse Masahiro Yamada
2018-11-22 3:14 ` Masahiro Yamada [this message]
2018-11-24 8:16 ` [PATCH v4 2/3] build_bug.h: remove negative-array fallback for BUILD_BUG_ON() Miguel Ojeda
2018-11-22 3:14 ` [PATCH v4 3/3] build_bug.h: remove most of dummy BUILD_BUG_ON stubs for Sparse Masahiro Yamada
2018-11-24 8:29 ` Miguel Ojeda
2018-11-22 3:25 ` [PATCH v4 1/3] kernel.h: disable type-checks in container_of() " Andrew Morton
2018-11-22 14:32 ` Luc Van Oostenryck
2018-11-24 8:24 ` Miguel Ojeda
2018-11-25 13:56 ` Masahiro Yamada
2018-12-01 3:34 ` Masahiro Yamada
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1542856462-18836-2-git-send-email-yamada.masahiro@socionext.com \
--to=yamada.masahiro@socionext.com \
--cc=akpm@linux-foundation.org \
--cc=josh@joshtriplett.org \
--cc=keescook@chromium.org \
--cc=linux-kernel@vger.kernel.org \
--cc=luc.vanoostenryck@gmail.com \
--cc=ndesaulniers@google.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).