[PATCH] Regulator: Suppress compiler warnings

[PATCH] Regulator: Suppress compiler warnings

[Keith Busch]

Some compilers complain of possible uninitialized variable usage, like
the following:

  drivers/regulator/helpers.c: In function ‘regulator_get_bypass_regmap’:
  drivers/regulator/helpers.c:463:16: warning: ‘val’ may be used uninitialized in this function [-Wuninitialized]

The code is safe though, and only uses the variables if they were
successfully set, so suppressing the warning with uninitialized_val.

Signed-off-by: Keith Busch <keith.busch@intel.com>
---
 drivers/regulator/helpers.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/regulator/helpers.c b/drivers/regulator/helpers.c
index 3bbb326..bb5b22a 100644
--- a/drivers/regulator/helpers.c
+++ b/drivers/regulator/helpers.c
@@ -30,7 +30,7 @@
  */
 int regulator_is_enabled_regmap(struct regulator_dev *rdev)
 {
-	unsigned int val;
+	unsigned int uninitialized_var(val);
 	int ret;
 
 	ret = regmap_read(rdev->regmap, rdev->desc->enable_reg, &val);
@@ -114,7 +114,7 @@ EXPORT_SYMBOL_GPL(regulator_disable_regmap);
  */
 int regulator_get_voltage_sel_regmap(struct regulator_dev *rdev)
 {
-	unsigned int val;
+	unsigned int uninitialized_var(val);
 	int ret;
 
 	ret = regmap_read(rdev->regmap, rdev->desc->vsel_reg, &val);
@@ -453,7 +453,7 @@ EXPORT_SYMBOL_GPL(regulator_set_bypass_regmap);
  */
 int regulator_get_bypass_regmap(struct regulator_dev *rdev, bool *enable)
 {
-	unsigned int val;
+	unsigned int uninitialized_var(val);
 	int ret;
 
 	ret = regmap_read(rdev->regmap, rdev->desc->bypass_reg, &val);
-- 
1.7.10.4

Re: [PATCH] Regulator: Suppress compiler warnings

[Krzysztof Kozlowski]

2015-09-01 1:41 GMT+09:00 Keith Busch <keith.busch@intel.com>:
> Some compilers complain of possible uninitialized variable usage, like
> the following:
>
>   drivers/regulator/helpers.c: In function ‘regulator_get_bypass_regmap’:
>   drivers/regulator/helpers.c:463:16: warning: ‘val’ may be used uninitialized in this function [-Wuninitialized]
>
> The code is safe though, and only uses the variables if they were
> successfully set, so suppressing the warning with uninitialized_val.
>
> Signed-off-by: Keith Busch <keith.busch@intel.com>
> ---
>  drivers/regulator/helpers.c |    6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/regulator/helpers.c b/drivers/regulator/helpers.c
> index 3bbb326..bb5b22a 100644
> --- a/drivers/regulator/helpers.c
> +++ b/drivers/regulator/helpers.c
> @@ -30,7 +30,7 @@
>   */
>  int regulator_is_enabled_regmap(struct regulator_dev *rdev)
>  {
> -       unsigned int val;
> +       unsigned int uninitialized_var(val);
>         int ret;
>
>         ret = regmap_read(rdev->regmap, rdev->desc->enable_reg, &val);

This is quite common pattern so such work-around should be added to
many other functions leading to code obfuscation. Which compiler do
you have in mind?

Best regards,
Krzysztof

> @@ -114,7 +114,7 @@ EXPORT_SYMBOL_GPL(regulator_disable_regmap);
>   */
>  int regulator_get_voltage_sel_regmap(struct regulator_dev *rdev)
>  {
> -       unsigned int val;
> +       unsigned int uninitialized_var(val);
>         int ret;
>
>         ret = regmap_read(rdev->regmap, rdev->desc->vsel_reg, &val);
> @@ -453,7 +453,7 @@ EXPORT_SYMBOL_GPL(regulator_set_bypass_regmap);
>   */
>  int regulator_get_bypass_regmap(struct regulator_dev *rdev, bool *enable)
>  {
> -       unsigned int val;
> +       unsigned int uninitialized_var(val);
>         int ret;
>
>         ret = regmap_read(rdev->regmap, rdev->desc->bypass_reg, &val);
> --
> 1.7.10.4
>
> --
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Re: [PATCH] Regulator: Suppress compiler warnings

[Mark Brown]

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On Tue, Sep 01, 2015 at 09:52:13AM +0900, Krzysztof Kozlowski wrote:
> 2015-09-01 1:41 GMT+09:00 Keith Busch <keith.busch@intel.com>:
> > Some compilers complain of possible uninitialized variable usage, like
> > the following:

> >   drivers/regulator/helpers.c: In function ‘regulator_get_bypass_regmap’:
> >   drivers/regulator/helpers.c:463:16: warning: ‘val’ may be used uninitialized in this function [-Wuninitialized]

> > The code is safe though, and only uses the variables if they were
> > successfully set, so suppressing the warning with uninitialized_val.

> >  int regulator_is_enabled_regmap(struct regulator_dev *rdev)
> >  {
> > -       unsigned int val;
> > +       unsigned int uninitialized_var(val);
> >         int ret;
> >
> >         ret = regmap_read(rdev->regmap, rdev->desc->enable_reg, &val);

> This is quite common pattern so such work-around should be added to
> many other functions leading to code obfuscation. Which compiler do
> you have in mind?

Right, plus this will shut up valid compiler warnings which is poor
practice anyway.  I'd say this is a bug in the compiler.

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Re: [PATCH] Regulator: Suppress compiler warnings

[Keith Busch]

On Tue, 1 Sep 2015, Mark Brown wrote:
> On Tue, Sep 01, 2015 at 09:52:13AM +0900, Krzysztof Kozlowski wrote:
>> 2015-09-01 1:41 GMT+09:00 Keith Busch <keith.busch@intel.com>:
>>>  int regulator_is_enabled_regmap(struct regulator_dev *rdev)
>>>  {
>>> -       unsigned int val;
>>> +       unsigned int uninitialized_var(val);
>>>         int ret;
>>>
>>>         ret = regmap_read(rdev->regmap, rdev->desc->enable_reg, &val);
>
>> This is quite common pattern so such work-around should be added to
>> many other functions leading to code obfuscation. Which compiler do
>> you have in mind?
>
> Right, plus this will shut up valid compiler warnings which is poor
> practice anyway.  I'd say this is a bug in the compiler.

Using gcc 4.7.2 with '-Os'. The warning does not happen when that option
is not used, i.e. disable CONFIG_CC_OPTIMIZE_FOR_SIZE.

I will certainly try other gcc versions with the same config and see
what happens.