gdb stops working for Qt program ???

[enno]

Running a simple program

int main(int argc, char **argv) {
  QApplication myApp(argc, argv);
}

int main(int argc, char **argv) {
  QApplication myApp(argc, argv);
}

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built with qmake CONFIG += debug runs under gdb and after the only statement

gdb> p myApp

gdb> p myApp

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prints all the normal info about a QApplication object. So I think debug libraries etc. are all in place and properly configured.

In a more complex program stopping after the QApplication creation gdb is only prepared to report

(gdb) p myApp
$3 = <incomplete type>

(gdb) p myApp
$3 = <incomplete type>

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and debugging properties or methods of Qt objects fails although the program compiles, links and executes properly except for one or two functions.

Could any of the following upset gdb:
1. Linking with a plain C objects from another directory
2. Linking with libtiff and/or libusb-1.0
3. Using a number of struct rather than classes
I think all these are acceptable but any ideas as to what upsets gdb are welcome.

PS. I could pare down my program until gdb starts working but that is very timeconsuming because of all interrelationsships. Would love a simpler list of things to try.

All suggestions welcome.
Enno.