Re: [PATCH] Revert "ALSA: firewire-lib: change structure member with proper type"

[Takashi Iwai <tiwai@suse.de>]

On Thu, 05 Jan 2017 01:41:31 +0100,
Takashi Sakamoto wrote:
> 
> This reverts commit 6b7e95d1336b9eb0d4c6db190ce756480496bd13. This commit
> is based on a concern about value of the given parameter. It's expected
> to be ORed value with some enumeration-constants, thus often it can not be
> one of the enumeration-constants. I understood that this is out of
> specification and causes implementation-dependent issues.
> 
> In C language specification, enumerated type can be interpreted as an
> integer type, in which all of enumeration-constants in corresponding
> enumerator-list can be stored. Implementations can select one of char,
> signed int and unsigned int as its type, and this selection is
> implementation-dependent.
> 
> In GCC, a signed integer is selected when at least one of
> enumeration-constants has negative value, else an unsigned integer is
> selected. This behaviour can be switched by -fshort-enums to short type.
> Anyway, the type can be decided after scanning all of
> enumeration-constants.
> 
> Totally, there's no rules to constrain the value of enumerated type to
> be one of enumeration-constants. In short, in enumerated type, decision
> of actual type for the type is the most important and
> enumeration-constants are just used for the decision, thus it's permitted
> to have an integer value in a range of enumeration-constants. In our case,
> actual type for the type is currently deterministic to be either char or
> unsigned int. Under GCC, it's unsigned int.

You sign-off is missing.


Takashi