linux-kernel - [PATCH 4.4 10/22] ACPI: fix false-positive -Wuninitialized warning

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Message-Id: <20190805124920.863235287@linuxfoundation.org>
Date:   Mon,  5 Aug 2019 15:02:47 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Arnd Bergmann <arnd@...db.de>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Nathan Chancellor <natechancellor@...il.com>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.4 10/22] ACPI: fix false-positive -Wuninitialized warning

[ Upstream commit dfd6f9ad36368b8dbd5f5a2b2f0a4705ae69a323 ]

clang gets confused by an uninitialized variable in what looks
to it like a never executed code path:

arch/x86/kernel/acpi/boot.c:618:13: error: variable 'polarity' is uninitialized when used here [-Werror,-Wuninitialized]
        polarity = polarity ? ACPI_ACTIVE_LOW : ACPI_ACTIVE_HIGH;
                   ^~~~~~~~
arch/x86/kernel/acpi/boot.c:606:32: note: initialize the variable 'polarity' to silence this warning
        int rc, irq, trigger, polarity;
                                      ^
                                       = 0
arch/x86/kernel/acpi/boot.c:617:12: error: variable 'trigger' is uninitialized when used here [-Werror,-Wuninitialized]
        trigger = trigger ? ACPI_LEVEL_SENSITIVE : ACPI_EDGE_SENSITIVE;
                  ^~~~~~~
arch/x86/kernel/acpi/boot.c:606:22: note: initialize the variable 'trigger' to silence this warning
        int rc, irq, trigger, polarity;
                            ^
                             = 0

This is unfortunately a design decision in clang and won't be fixed.

Changing the acpi_get_override_irq() macro to an inline function
reliably avoids the issue.

Signed-off-by: Arnd Bergmann <arnd@...db.de>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Reviewed-by: Nathan Chancellor <natechancellor@...il.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 include/linux/acpi.h | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/include/linux/acpi.h b/include/linux/acpi.h
index 3672893b275ed..6a30f1e03aa9e 100644
--- a/include/linux/acpi.h
+++ b/include/linux/acpi.h
@@ -226,7 +226,10 @@ void acpi_set_irq_model(enum acpi_irq_model_id model,
 #ifdef CONFIG_X86_IO_APIC
 extern int acpi_get_override_irq(u32 gsi, int *trigger, int *polarity);
 #else
-#define acpi_get_override_irq(gsi, trigger, polarity) (-1)
+static inline int acpi_get_override_irq(u32 gsi, int *trigger, int *polarity)
+{
+	return -1;
+}
 #endif
 /*
  * This function undoes the effect of one call to acpi_register_gsi().
-- 
2.20.1