linux-kernel - [PATCH 4/6] dynamic_debug: Wrap section comparison in dynamic_debug_init with COMPARE

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Date:   Tue, 18 Feb 2020 21:54:21 -0700
From:   Nathan Chancellor <natechancellor@...il.com>
To:     Masahiro Yamada <masahiroy@...nel.org>,
        Michal Marek <michal.lkml@...kovi.net>,
        Arnd Bergmann <arnd@...db.de>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...hat.com>,
        Jason Baron <jbaron@...mai.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-kernel@...r.kernel.org, linux-kbuild@...r.kernel.org,
        linux-arch@...r.kernel.org, linux-mm@...ck.org,
        clang-built-linux@...glegroups.com,
        Nathan Chancellor <natechancellor@...il.com>
Subject: [PATCH 4/6] dynamic_debug: Wrap section comparison in dynamic_debug_init with COMPARE_SECTIONS

Clang warns:

../lib/dynamic_debug.c:1016:24: warning: array comparison always
evaluates to false [-Wtautological-compare]
        if (__start___verbose == __stop___verbose) {
                              ^
1 warning generated.

These are not true arrays, they are linker defined symbols, which are
just addresses so there is not a real issue here. Use the
COMPARE_SECTIONS macro to silence this warning by casting the linker
defined symbols to unsigned long, which keeps the logic the same.

Link: https://github.com/ClangBuiltLinux/linux/issues/765
Signed-off-by: Nathan Chancellor <natechancellor@...il.com>
---
 lib/dynamic_debug.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
index aae17d9522e5..c7350aa6e853 100644
--- a/lib/dynamic_debug.c
+++ b/lib/dynamic_debug.c
@@ -1031,7 +1031,7 @@ static int __init dynamic_debug_init(void)
 	int n = 0, entries = 0, modct = 0;
 	int verbose_bytes = 0;
 
-	if (__start___verbose == __stop___verbose) {
+	if (COMPARE_SECTIONS(__start___verbose, ==, __stop___verbose)) {
 		pr_warn("_ddebug table is empty in a CONFIG_DYNAMIC_DEBUG build\n");
 		return 1;
 	}
-- 
2.25.1