[Development] FW: Backwards compatibiltiy break in Qt 5.5

[Thiago Macieira]

On Monday 27 July 2015 16:54:49 Knoll Lars wrote:
> QChar::isPrint() is not that expensive, and this is about debug output. Your
> code escaping all these chars is a more expensive if it gets hit. 

I don't think so. The code is pretty efficient and it's just a simple stateful 
loop. QChar::isPrint requires an out-of-line function call for every character 
and then looking it up in our Unicode tables. That's a lot of data for the L1 
cache: qstring.o's .rodata section is 188200 bytes.

> And I don't see how homographs are a problem for debug output. Unless you're
> debugging certain rather special cases in which case you should be able to
> turn full escaping on. I would guess that 98% of our users are using qDebug
> differently than you are.

That is again what I am trying to avoid: having to know that you need this 
before you actually see the problem.

In any case, if we want to escape characters < 32, we need to escape the 
backslash too, which also was a source of complaints in the bug report, as

	"C:\Users"

became

	"C:\\Users"

Nikolai didn't include this in his mail to the list.

-- 
Thiago Macieira - thiago.macieira (AT) intel.com
  Software Architect - Intel Open Source Technology Center