Gabriel M. Beddingfield wrote:
> Hi Sebastian,
>
> On Tue, 5 Jan 2010, Sebastian Moors wrote:
>
>
>> I've just read all the other mails concerning the logger class and a few
>> questions popped out of mind..
>> If i understand it correct, the new proposal uses something like
>> INFOLOG( const char* , .. ) instead of INFOLOG( const QString ). Why is
>> this faster? Is it just the fact the we don't have to pass the QString
>> by value, which results in an expensive call to the copy constructor ?
>>
> Correct on the change to INFOLOG.
>
> The objective isn't to be /faster/, but to be real-time
> safe. QString::QString(...) and QString::operator=(const
> QString&) are not real-time safe because they allocate
> memory dynamically (i.e. they use 'new'). You must not do
> this in a real-time thread.
>
> We currently work around this by wrapping the code inside an
> integer check. Something like:
>
> if( Logger::log_level()& Logger::Info ) {
> Logger::log(Logger::Info, message, ... );
> }
>
> This avoids invoking QString's methods unless the logging
> level is set sufficiently high.
>
> But if you /do/ set the log level high, you risk becoming a
> JACK zombie while you wait on `new QChar`.
>
> The proposal would use strings that are allocated on the
> stack or pre-allocated in a buffer.
>
> As a side benefit, these strings will also run faster
> becaus. However, you give up the benefits of having unicode
> strings.
>
Thanks, your explanation of the allocation problem made it clear!
- Sebastian
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