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From: Nathan Chancellor <natechancellor@gmail.com>
To: Masahiro Yamada <masahiroy@kernel.org>,
	Michal Marek <michal.lkml@markovi.net>,
	Arnd Bergmann <arnd@arndb.de>,
	Steven Rostedt <rostedt@goodmis.org>,
	Ingo Molnar <mingo@redhat.com>, Jason Baron <jbaron@akamai.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Andrew Morton <akpm@linux-foundation.org>
Cc: linux-kernel@vger.kernel.org, linux-kbuild@vger.kernel.org,
	linux-arch@vger.kernel.org, linux-mm@kvack.org,
	clang-built-linux@googlegroups.com,
	Nathan Chancellor <natechancellor@gmail.com>
Subject: [PATCH 3/6] tracing: Wrap section comparison in tracer_alloc_buffers with COMPARE_SECTIONS
Date: Tue, 18 Feb 2020 21:54:20 -0700	[thread overview]
Message-ID: <20200219045423.54190-4-natechancellor@gmail.com> (raw)
In-Reply-To: <20200219045423.54190-1-natechancellor@gmail.com>

Clang warns:

../kernel/trace/trace.c:9335:33: warning: array comparison always
evaluates to true [-Wtautological-compare]
        if (__stop___trace_bprintk_fmt != __start___trace_bprintk_fmt)
                                       ^
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@gmail.com>
---
 kernel/trace/trace.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index c797a15a1fc7..e1f3b16e457b 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -9332,7 +9332,7 @@ __init static int tracer_alloc_buffers(void)
 		goto out_free_buffer_mask;
 
 	/* Only allocate trace_printk buffers if a trace_printk exists */
-	if (__stop___trace_bprintk_fmt != __start___trace_bprintk_fmt)
+	if (COMPARE_SECTIONS(__stop___trace_bprintk_fmt, !=, __start___trace_bprintk_fmt))
 		/* Must be called before global_trace.buffer is allocated */
 		trace_printk_init_buffers();
 
-- 
2.25.1


  parent reply	other threads:[~2020-02-19  4:54 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-19  4:54 [PATCH 0/6] Silence some instances of -Wtautological-compare and enable globally Nathan Chancellor
2020-02-19  4:54 ` [PATCH 1/6] asm/sections: Add COMPARE_SECTIONS macro Nathan Chancellor
2020-02-19  4:54 ` [PATCH 2/6] kernel/extable: Wrap section comparison in sort_main_extable with COMPARE_SECTIONS Nathan Chancellor
2020-02-19  4:54 ` Nathan Chancellor [this message]
2020-02-19 14:34   ` [PATCH 3/6] tracing: Wrap section comparison in tracer_alloc_buffers " Steven Rostedt
2020-02-19 17:44     ` Nick Desaulniers
2020-02-19 18:16       ` Jason Gunthorpe
2020-02-19 19:09         ` Steven Rostedt
2020-02-19 19:11         ` Nick Desaulniers
2020-02-19 19:22           ` Nathan Chancellor
2020-02-19 19:43             ` Steven Rostedt
2020-02-19 19:54           ` Jason Gunthorpe
2020-02-19 21:32             ` Nick Desaulniers
2020-02-19  4:54 ` [PATCH 4/6] dynamic_debug: Wrap section comparison in dynamic_debug_init " Nathan Chancellor
2020-02-19  4:54 ` [PATCH 5/6] mm: kmemleak: Wrap section comparison in kmemleak_init " Nathan Chancellor
2020-02-19  4:54 ` [PATCH 6/6] kbuild: Enable -Wtautological-compare Nathan Chancellor
2020-04-21  4:03 ` [PATCH 0/6] Silence some instances of -Wtautological-compare and enable globally Andrew Morton
2020-04-21  4:32   ` Nathan Chancellor

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