[Qt-creator] Debugging helper for forward declared classes (PIMPL)

resurrection at centrum.cz resurrection at centrum.cz
Sun May 12 17:05:16 CEST 2019

Thanks, this works!
I have only one problem with this. When the type of a field is another complex type for which a debugging helper exists (e.g. QString) instead of using that helper for that type it puts there the Python object representation, e.g.: 
def qdump__MyType(d, value):
    address = d.extractPointer(value["d"])
    ptr = d.createValue(address, "void*")
    name = ptr.split("{QString}")
    with Children(d):
        with SubItem(d, "Name"):
The value that appears during debugging is:
I can work around this by copying the logic from the particular debugging helper (mine or Qt's) but I would expect it to be picked up automatically or that I could somehow call it myself. I must be missing something yet.
> Od: "André Pönitz" <apoenitz at t-online.de>
> Komu: resurrection at centrum.cz
> Datum: 12.05.2019 13:50
> Předmět: Re: [Qt-creator] Debugging helper for forward declared classes (PIMPL)
On Sun, May 12, 2019 at 12:42:33PM +0200, resurrection at centrum.cz wrote:
 > I have a problem creating a debugging helper for classes that does use only
 > forward-declared data member like when using PIMPL:
 > - MyClass.h
 >     struct MyClassPrivate;
 >     class MyClass
 >     {
 >         MyClassPrivate *d;
 >     };
 > - MyClass.cpp
 >     struct MyClassPrivate
 >     {
 >         int i;
 >     };
 >     //...
 > And the debugging helper:
 > def qdump__MyClass(d, value):
 >     with Children(d):
 >         d.putSubItem("Number", value["d"]["i"])
 > Only place when debugging helper for MyClass works is in the implementation file of
 > MyClass.cpp. In all other places the MyClassPrivate is just forward declared type and
 > the pointer to it is completely opaque to the debugging helper engine unless I step into
 > the MyClass.cpp where the type is defined.    I may be asking for the impossible, but is
 > there a way to work around this somehow? 
 When you know the layout of the private class, you can direcly operate on that. 
 E.g.  value.split('...') e.g. works similar to Python's  struct.unpack('...')
 I actually prefer this approach nowadays for rarely changing types as it does
 not require any debug information for the type, just the address of an instance. 

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