[PATCH] selftests/alsa: remove 0/NULL global variable assignment

[PATCH] selftests/alsa: remove 0/NULL global variable assignment

[Nikola Z. Ivanov]

Remove 0/NULL global variable assignment in mixer-test.c and pcm-test.c

Signed-off-by: Nikola Z. Ivanov <zlatistiv@gmail.com>
---
 tools/testing/selftests/alsa/mixer-test.c | 8 ++++----
 tools/testing/selftests/alsa/pcm-test.c   | 8 ++++----
 2 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/tools/testing/selftests/alsa/mixer-test.c b/tools/testing/selftests/alsa/mixer-test.c
index 2a4b2662035e..e113dafa5c24 100644
--- a/tools/testing/selftests/alsa/mixer-test.c
+++ b/tools/testing/selftests/alsa/mixer-test.c
@@ -53,10 +53,10 @@ struct ctl_data {
 	struct ctl_data *next;
 };
 
-int num_cards = 0;
-int num_controls = 0;
-struct card_data *card_list = NULL;
-struct ctl_data *ctl_list = NULL;
+int num_cards;
+int num_controls;
+struct card_data *card_list;
+struct ctl_data *ctl_list;
 
 static void find_controls(void)
 {
diff --git a/tools/testing/selftests/alsa/pcm-test.c b/tools/testing/selftests/alsa/pcm-test.c
index dbd7c222ce93..ce92548670c8 100644
--- a/tools/testing/selftests/alsa/pcm-test.c
+++ b/tools/testing/selftests/alsa/pcm-test.c
@@ -30,7 +30,7 @@ struct card_data {
 	struct card_data *next;
 };
 
-struct card_data *card_list = NULL;
+struct card_data *card_list;
 
 struct pcm_data {
 	snd_pcm_t *handle;
@@ -43,10 +43,10 @@ struct pcm_data {
 	struct pcm_data *next;
 };
 
-struct pcm_data *pcm_list = NULL;
+struct pcm_data *pcm_list;
 
-int num_missing = 0;
-struct pcm_data *pcm_missing = NULL;
+int num_missing;
+struct pcm_data *pcm_missing;
 
 snd_config_t *default_pcm_config;
 
-- 
2.50.1

Re: [PATCH] selftests/alsa: remove 0/NULL global variable assignment

[Mark Brown]

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On Thu, Aug 21, 2025 at 11:01:32PM +0300, Nikola Z. Ivanov wrote:
> Remove 0/NULL global variable assignment in mixer-test.c and pcm-test.c

Why?

> --- a/tools/testing/selftests/alsa/mixer-test.c
> +++ b/tools/testing/selftests/alsa/mixer-test.c
> @@ -53,10 +53,10 @@ struct ctl_data {
>  	struct ctl_data *next;
>  };
>  
> -int num_cards = 0;
> -int num_controls = 0;
> -struct card_data *card_list = NULL;
> -struct ctl_data *ctl_list = NULL;
> +int num_cards;
> +int num_controls;
> +struct card_data *card_list;
> +struct ctl_data *ctl_list;

Nothing now sets initial values for these variables so they all have
undefined values which is buggy.  The code is relying on the default
values.

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Re: [PATCH] selftests/alsa: remove 0/NULL global variable assignment

[Nikola Ivanov]

On Thu, Aug 21, 2025 at 09:49:29PM +0100, Mark Brown wrote:
> On Thu, Aug 21, 2025 at 11:01:32PM +0300, Nikola Z. Ivanov wrote:
> > Remove 0/NULL global variable assignment in mixer-test.c and pcm-test.c
>
> Why?
>
> > --- a/tools/testing/selftests/alsa/mixer-test.c
> > +++ b/tools/testing/selftests/alsa/mixer-test.c
> > @@ -53,10 +53,10 @@ struct ctl_data {
> >     struct ctl_data *next;
> >  };
> >
> > -int num_cards = 0;
> > -int num_controls = 0;
> > -struct card_data *card_list = NULL;
> > -struct ctl_data *ctl_list = NULL;
> > +int num_cards;
> > +int num_controls;
> > +struct card_data *card_list;
> > +struct ctl_data *ctl_list;
>
> Nothing now sets initial values for these variables so they all have
> undefined values which is buggy.  The code is relying on the default
> values.

Checkpatch reports it as an error, it looks to be part of the C
standard that all compilers must initialize globals to 0.
Though I suppose it helps with readability to see
the num_ counters assigned 0.

Re: [PATCH] selftests/alsa: remove 0/NULL global variable assignment

[Mark Brown]

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On Fri, Aug 22, 2025 at 12:17:14AM +0300, Nikola Ivanov wrote:
> On Thu, Aug 21, 2025 at 09:49:29PM +0100, Mark Brown wrote:

> > > -int num_cards = 0;
> > > -int num_controls = 0;
> > > -struct card_data *card_list = NULL;
> > > -struct ctl_data *ctl_list = NULL;
> > > +int num_cards;
> > > +int num_controls;
> > > +struct card_data *card_list;
> > > +struct ctl_data *ctl_list;

> > Nothing now sets initial values for these variables so they all have
> > undefined values which is buggy.  The code is relying on the default
> > values.

> Checkpatch reports it as an error, it looks to be part of the C
> standard that all compilers must initialize globals to 0.
> Though I suppose it helps with readability to see
> the num_ counters assigned 0.

Do you have a reference there, note that these are just plain non-static
variables?  I wouldn't trust checkpatch for anything that isn't kernel
code (and even there it's got issues).

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Re: [PATCH] selftests/alsa: remove 0/NULL global variable assignment

[Nikola Z. Ivanov]

On Thu, Aug 21, 2025 at 10:30:50PM +0100, Mark Brown wrote:
> On Fri, Aug 22, 2025 at 12:17:14AM +0300, Nikola Ivanov wrote:
> > On Thu, Aug 21, 2025 at 09:49:29PM +0100, Mark Brown wrote:
> 
> > > > -int num_cards = 0;
> > > > -int num_controls = 0;
> > > > -struct card_data *card_list = NULL;
> > > > -struct ctl_data *ctl_list = NULL;
> > > > +int num_cards;
> > > > +int num_controls;
> > > > +struct card_data *card_list;
> > > > +struct ctl_data *ctl_list;
> 
> > > Nothing now sets initial values for these variables so they all have
> > > undefined values which is buggy.  The code is relying on the default
> > > values.
> 
> > Checkpatch reports it as an error, it looks to be part of the C
> > standard that all compilers must initialize globals to 0.
> > Though I suppose it helps with readability to see
> > the num_ counters assigned 0.
> 
> Do you have a reference there, note that these are just plain non-static
> variables?  I wouldn't trust checkpatch for anything that isn't kernel
> code (and even there it's got issues).


This is what it says in the C99/C11/C18/C23 drafts I found:

> If an object that has automatic storage duration is not initialized explicitly, its value is
> indeterminate. If an object that has static or thread storage duration is not initialized
> explicitly, then:
> — if it has pointer type, it is initialized to a null pointer;
> — if it has arithmetic type, it is initialized to (positive or unsigned) zero;

"static or thread storage" referring to variables declared at global scope 
(regardless of static keyword) as well as those inside function scope defined
with static keyword.

Since as you said checkpatch.pl is mostly intended for kernel code
(which I was not aware of) this patch is probably not desired.
In case it still is I can add quote to the draft and link it in the patch.

Re: [PATCH] selftests/alsa: remove 0/NULL global variable assignment

[Mark Brown]

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On Fri, Aug 22, 2025 at 01:57:05AM +0300, Nikola Z. Ivanov wrote:
> On Thu, Aug 21, 2025 at 10:30:50PM +0100, Mark Brown wrote:

> > Do you have a reference there, note that these are just plain non-static
> > variables?  I wouldn't trust checkpatch for anything that isn't kernel
> > code (and even there it's got issues).

> This is what it says in the C99/C11/C18/C23 drafts I found:

...

> Since as you said checkpatch.pl is mostly intended for kernel code
> (which I was not aware of) this patch is probably not desired.
> In case it still is I can add quote to the draft and link it in the patch.

No, it's fine - thanks for checking the reference.  I suspected this
might be something specific to how the kernel is linked:

Reviewed-by: Mark Brown <broonie@kernel.org>

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Re: [PATCH] selftests/alsa: remove 0/NULL global variable assignment

[Takashi Iwai]

On Thu, 21 Aug 2025 22:01:32 +0200,
Nikola Z. Ivanov wrote:
> 
> Remove 0/NULL global variable assignment in mixer-test.c and pcm-test.c
> 
> Signed-off-by: Nikola Z. Ivanov <zlatistiv@gmail.com>

Applied now.  Thanks.


Takashi