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[PATCH 1/2] of: fix uninitialized variable warning for overlay test

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  [PATCH 1/2] of: fix uninitialized variable warning for overlay test Arnd Bergmann <arnd@arndb.de> - 2017-04-28 11:50 +0200
    Re: [PATCH 1/2] of: fix uninitialized variable warning for overlay  test Frank Rowand <frowand.list@gmail.com> - 2017-04-28 17:50 +0200

#1632737 — [PATCH 1/2] of: fix uninitialized variable warning for overlay test

gcc warns that an empty device tree would cause undefined behavior:

drivers/of/unittest.c: In function 'of_unittest':
drivers/of/unittest.c:2199:25: warning: 'last_sibling' may be used uninitialized in this function [-Wmaybe-uninitialized]

This adds an initialization of the variable to zero, which we handle
correctly.

Fixes: 81d0848fc8d2 ("of: Add unit tests for applying overlays")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 drivers/of/unittest.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/of/unittest.c b/drivers/of/unittest.c
index 12597ff8cfb0..6b8f3e6aa43c 100644
--- a/drivers/of/unittest.c
+++ b/drivers/of/unittest.c
@@ -2192,7 +2192,7 @@ static __init void of_unittest_overlay_high_level(void)
 
 	mutex_lock(&of_mutex);
 
-	for (np = of_root->child; np; np = np->sibling)
+	for (last_sibling = np = of_root->child; np; np = np->sibling)
 		last_sibling = np;
 
 	if (last_sibling)
-- 
2.9.0

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#1632983 — Re: [PATCH 1/2] of: fix uninitialized variable warning for overlay test

On 04/28/17 02:44, Arnd Bergmann wrote:
> gcc warns that an empty device tree would cause undefined behavior:
> 
> drivers/of/unittest.c: In function 'of_unittest':
> drivers/of/unittest.c:2199:25: warning: 'last_sibling' may be used uninitialized in this function [-Wmaybe-uninitialized]
> 
> This adds an initialization of the variable to zero, which we handle
> correctly.
> 
> Fixes: 81d0848fc8d2 ("of: Add unit tests for applying overlays")
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
>  drivers/of/unittest.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/of/unittest.c b/drivers/of/unittest.c
> index 12597ff8cfb0..6b8f3e6aa43c 100644
> --- a/drivers/of/unittest.c
> +++ b/drivers/of/unittest.c
> @@ -2192,7 +2192,7 @@ static __init void of_unittest_overlay_high_level(void)
>  
>  	mutex_lock(&of_mutex);
>  
> -	for (np = of_root->child; np; np = np->sibling)
> +	for (last_sibling = np = of_root->child; np; np = np->sibling)
>  		last_sibling = np;
>  
>  	if (last_sibling)
> 

Thanks Arnd!  Linux-next also reported this and I sent Rob a different
patch for it yesterday.

Rob, I am fine with either Arnd's patch or mine, they both fix the
problem.

-Frank

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