[Interest] Interest Digest, Vol 80, Issue 8

[Roland Hughes]

On 05/12/2018 08:57 AM, Thiago Macieira wrote:
> I'm claiming that Qt is run 1% of the time in big-endian mode. Explain to me
> why the 99% should perform the byte swap.

Because that class was created to communicate with the big-endian world 
of real computers. Do not change the default. Feel free to create a 
different class, QWannaBeDataStream or some such name, but there is an 
installed base of code in production expecting the existing default 
behavior.

Before anyone pipes up with a silly little "You should never rely on 
defaults" response, I will ask

Just how many of you physically initialize a QString at point of 
declaration?

None of you. The historical default behavior of the class is to 
initialize it.

Visualize somebody arbitrarily deciding that default was a needless 
processing burden so they took it out and rolled that code into the new 
baseline. Just how good is your code going to work?

If you're not statically compiled and not running on a locked down 
system (say a desktop application) the next automatic update from the 
repos will shoot your application out of the saddle without you doing a 
thing.

Think that is too much of a reach? Not a problem. How about we choose 
one which is already 99% of the way there?

There is/was a .configure option or some other method of building Qt 
from source which sets a fixed amount of preallocated string space. It's 
a speed improvement for embedded targets with really crappy dynamic 
memory allocation (most of them). How about someone realizing the 
battery operated embedded processors _all_ had crappy dynamic memory 
allocation and justifiably concluded the extra processor time on grid 
connected computers was just a trifle so they change the build default?

This one is sweet. You can diff the code until the cows come home, but 
you won't find the change. Not unless you go all the way out to the 
build stuff.

Sounds tiny doesn't it?

Well, if you preallocate 15 bytes/characters, a newly created "empty" 
string is now 15 bytes/characters long, not "". Just how many of you 
always use .isEmpty() instead of an empty string compare? I haven't 
opened up and looked at the isEmpty() code to see if it also honors the 
compiled in preallocation amount. It would be interesting, from an 
academic perspective, to see what it returns in the first two examples here:

https://doc.qt.io/archives/qt-4.8/qstring.html#isEmpty


Changing default behavior based on a single viewpoint, while a time 
honored AGILE tradition, is always a bad thing. Then again, AGILE is 
always a bad thing.

-- 
Roland Hughes, President
Logikal Solutions
(630)-205-1593

http://www.theminimumyouneedtoknow.com
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