Re: [boost] [log] Review-ready version in the Vault

Subject: Re: [boost] [log] Review-ready version in the Vault
From: Andrey Semashev (andrey.semashev_at_[hidden])
Date: 2009-02-11 14:28:31

vicente.botet wrote:
> 
>> I have some innocent questions: 
>> * Is logging thread-safe? 
>> * If yes, are the lines interleaved as it is the case for output streams? 
>> * If not could you point out how and where in the implementation this is handled?
> 
> Hi again,
> 
> well i have found some anwers to my questions on the document. I'll come back later on.

I'm glad you did. :)

> How a log record is recognized, i.e. I don't see std::endl neither std::flush are used in the examples. How many lines result in the following example if condifiton is true (2 or 3)
> 
>     src::logger_mt& lg = my_logger::get();
>     if (lg.open_record()) {
>         lg.strm() << "Hello ";
>         lg.strm() << "world!";
>     }

That one is not valid in the current implementation. It should be 
replaced with:

   if (lg.open_record())
     lg.strm() << "Hello ";
   if (lg.open_record())
     lg.strm() << "world!";

This is because strm() returns a temporary object that confirms the 
opened log record on its destruction. Once confirmed, the record is 
dispatched and cannot be modified, so a new record must be opened.

>     // do something
>     if (condition) {
>         if (lg.open_record()) lg.strm() << "Bye!";
>     }

Every complete streaming statement is a log record. So, you emit three 
records in your code sample, assuming that all conditions are true and 
the needed corrections are made.

> Can other logs be interleaved between "Hello " , "world!"  and Bye in a multi threaded program? 

Yes.