[Interest] Debugging very slow in my MainWindow

André Pönitz andre.poenitz at mathematik.tu-chemnitz.de
Fri Jun 7 19:52:02 CEST 2013


On Fri, Jun 07, 2013 at 12:59:38PM +0200, Etienne Sandré-Chardonnal wrote:
> Dear all,
> 
> When I'm debugging my project (gcc 32 and 64bit mingw-w64, Qt 4.8.1) under
> QtCreator (2.6.0), it's not ultra-fast, but usable, in most of my code.
> However, when stepping inside my MainWindow class, and especially when
> unrolling some "Locals and Expressions", it takes about 1min to respond, or
> sometimes more (but then I kill gdb since I'm not patient enough...)
> I tried to disable debug helpers, and it doesn't help.
> 
> Seems I feel that this comes from the local & expression retrieval by gdb, the
> details of my class are below.

It depends a lot on your version of GDB. Especially recent versions
exhibit severe performance regressions, to a degree that renders them
basically unsuitable for serious use.

See e.g. http://sourceware.org/bugzilla/show_bug.cgi?id=15412
or http://sourceware.org/bugzilla/show_bug.cgi?id=15519 

The problem seems to be related to the handling of type information
which is especially bad in the Qt Creator context because of the
heavy use of "pretty printing" for data display, which requires quite
a bit of type manipulation under the hood.

I would recommend to stick to GDB 7.4.1 (or something close to that)
as long as this unfortunate situation lasts. On Linux building GDB
from source is a straight-forward five-minute ./configure && make,
for MinGW you could try http://builds.qt-project.org/job/gdb-windows/

Andre'



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