[asterisk-dev] any difference between NULL and "" in struct ast_callerid fields ?

[Julian Lyndon-Smith]

FWIW, I would say that "<unknown>" is the best.

Julian.
Luigi Rizzo wrote:
> given the lack of feedback, I have started to fix the issues
> described below.
> 
> As it is now, the code maps NULL or "" into three different values,
> not in a completely consistent way:
> 
> 	""
> 	"unknown"
> 	"<unknown>"
> 
> what is the correct format ?
> 
> 	luigi
> 
> On Tue, Apr 18, 2006 at 09:50:59AM -0700, Luigi Rizzo wrote:
>> hi,
>> browsing throughout the code, i see that some places map
>> a NULL value in the struct ast_callerid fields to "<unknown>"
>> or similar string, but the empty string is left alone.
>>
>> However, i am not so sure that the behaviour is
>> consistent across the whole code, and especially,
>> i cannot see a reason why the empty string "" should
>> be treated differently from NULL.
>>
>> In many other places in asterisk, NULL and "" are considered the
>> same thing and we have plenty of utility functions code that assume
>> that.
>>
>> The reason is for this behaviour is an important one:
>>
>>     we have both dynamically and statically allocated strings, and the
>>     latter cannot store NULL and must represent it as an empty string.
>>
>> So, even if parts of the code that handle the CID fields
>> make use of the difference between NULL and "", there is a
>> huge risk that this difference is lost when passing values
>> around between different types of buffers.
>>
>> As a consequence, unless there are convincing explaination
>> on why we need to differentiate that, I am going to add
>> comments, in include/asterisk/channel.h, that in the ast_callerid
>> fields, NULL and "" are considered equivalent, and then start
>> making the code consistent with the above spec.
>>
>> comments welcome.
>>
>> 	cheers
>> 	luigi
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