linux-kernel - [PATCH 3.16 159/178] ACPI / power: Avoid maybe-uninitialized warning

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Message-ID: <lsq.1500213406.910614065@decadent.org.uk>
Date:   Sun, 16 Jul 2017 14:56:46 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        "Arnd Bergmann" <arnd@...db.de>
Subject: [PATCH 3.16 159/178] ACPI / power: Avoid maybe-uninitialized warning

3.16.46-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Arnd Bergmann <arnd@...db.de>

commit fe8c470ab87d90e4b5115902dd94eced7e3305c3 upstream.

gcc -O2 cannot always prove that the loop in acpi_power_get_inferred_state()
is enterered at least once, so it assumes that cur_state might not get
initialized:

drivers/acpi/power.c: In function 'acpi_power_get_inferred_state':
drivers/acpi/power.c:222:9: error: 'cur_state' may be used uninitialized in this function [-Werror=maybe-uninitialized]

This sets the variable to zero at the start of the loop, to ensure that
there is well-defined behavior even for an empty list. This gets rid of
the warning.

The warning first showed up when the -Os flag got removed in a bug fix
patch in linux-4.11-rc5.

I would suggest merging this addon patch on top of that bug fix to avoid
introducing a new warning in the stable kernels.

Fixes: 61b79e16c68d (ACPI: Fix incompatibility with mcount-based function graph tracing)
Signed-off-by: Arnd Bergmann <arnd@...db.de>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/acpi/power.c | 1 +
 1 file changed, 1 insertion(+)

--- a/drivers/acpi/power.c
+++ b/drivers/acpi/power.c
@@ -201,6 +201,7 @@ static int acpi_power_get_list_state(str
 		return -EINVAL;
 
 	/* The state of the list is 'on' IFF all resources are 'on'. */
+	cur_state = 0;
 	list_for_each_entry(entry, list, node) {
 		struct acpi_power_resource *resource = entry->resource;
 		acpi_handle handle = resource->device.handle;