[dpdk-dev] [PATCH 01/13] eal/log: introduce log register macro

[Andrew Rybchenko]

On 6/24/20 6:32 PM, Jerin Jacob wrote:
> On Wed, Jun 24, 2020 at 8:56 PM Andrew Rybchenko
> <arybchenko at solarflare.com> wrote:
>>
>> On 6/24/20 4:11 PM, Jerin Jacob wrote:
>>> On Wed, Jun 17, 2020 at 3:51 PM Andrew Rybchenko
>>> <arybchenko at solarflare.com> wrote:
>>>>
>>>> On 6/17/20 1:02 PM, David Marchand wrote:
>>>>> On Wed, Jun 17, 2020 at 8:30 AM <jerinj at marvell.com> wrote:
>>>>>>
>>>>>> From: Jerin Jacob <jerinj at marvell.com>
>>>>>>
>>>>>> Introducing the RTE_LOG_REGISTER macro to avoid the code duplication
>>>>>> in the log registration process.
>>>>>>
>>>>>> It is a wrapper macro for declaring the logtype, register the log and sets
>>>>>
>>>>> Having the logtype variable declared as part of the macro will force
>>>>> us to have global symbols (for the cases where it is needed).
>>>>> I'd rather leave the declaration to the caller, and only handle the
>>>>> registering part in this macro.
>>>>
>>>> I agree with David that it is important to avoid global symbols
>>>> when it is not needed.
>>>
>>> David, Andrew,
>>>
>>> Since it is executed in "constructor" context, it will be always from
>>> the global variable. Right?
>>> i.e DPDK is not yet initialized in when "constructor" being called.
>>> In addition to that, It will be adding more lines of code in the
>>> consumer of this MACRO.
>>> Thoughts?
>>
>> The problem is rather 'extern' vs 'static'. Before the patch
>> many variables are static, but become externally visible after
>> the patch.
> 
> OK. How about RTE_LOG_REGISTER_EXTERN or RTE_LOG_REGISTER_STATIC then?
> It will allow less code in the consumer of this macro.
> May be default we an make it as static so RTE_LOG_REGISTER and
> RTE_LOG_REGISTER_EXTERN
> for the different needs.
> 
> Thoughts?

Yes, I think it is a possible solution to use static in
RTE_LOG_REGISTER and use RTE_LOG_REGISTER_EXTERN
for non-static version. If we go this way, I'd prefer
the option.

Alternative is to keep variable declaration outside,
as David suggested, and I tend to agree that it is a
bit better. Macro name says 'register'. It is not
'declare and register'. Also it avoids static-vs-extern
problem completely. The solution allows to keep the
variable declaration untouched and put constructor (macro)
at the end of fine where constructors typically reside.