[alsa-devel] Compiler warning - overriding codec compress type

Clemens Ladisch clemens at ladisch.de
Mon Apr 18 11:25:43 CEST 2011

Patrick Lai wrote:
> I got a compiler warning soc-core.c: In function
> 'snd_soc_instantiate_cards' warning: 'compress_type' may be used
> uninitialized in this function. In reality, compress_type is defined as
> local variable in snd_soc_instantiate_card().

Please note that this warning is merely a tool to find errors in the
code; the word "may" indicates that the compilter isn't sure about this.

> I think the fix should look like the following:
> list_for_each_entry(codec, &codec_list, list) {
>                  if (codec->cache_init)
>                          continue;
> +               compress_type = 0;
>                  /* check to see if we need to override the compress_type */
>                  for (i = 0; i < card->num_configs; ++i) {
>                          codec_conf = &card->codec_conf[i];

When the for loop does not find an override, the following if() will
jump out of the outer list_for_each_entry loop before the compress_type
could be used, so it is not actually necessary to initialize this
variable; a better way would be to use uninitialized_var.

> My kernel version is 2.6.38. Has the warning being addressed in 2.6.39 
> or 2.6.40 patches?

... and an even better way is to simplify the logic:


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