CMake errors cause Qt Creator configuration to become unresponsive.
For many versions now the Qt Creator IDE has been integrated with CMake and the most recent versions take over the management of CMake configuration variables. However, the most recent versions of these two tools are using the server-mode feature of CMake, and this is causing a problem when the configuration is in a temporarily invalid state.
The problem happens when Qt Creator runs CMake and CMake has a configuration error. When this happens, the Qt Creator project build settings dialog where you set CMake variables becomes non-responsive. That is, if the run of CMake fails to successfully generate all its files, you cannot do anything with the project in Qt Creator. Most of the time you solve CMake configure failures by changing CMake variables, which is a problem because at this point Qt Creator does not let you change any CMake variables.
This simple CMakeLists.txt file demonstrates the issue. It contains a single option that must be turned off for the configure to succeed. If you try to open this as a project in Qt Creator, the CMake configure will fail and you won't be able to turn the option off.
Frankly, I'm a bit shocked no one has run into this before me. It is rare for me to configure a software project that did not require me to set something like a library configuration through CMake variables.
I am currently using CMake 3.10.2 and Qt Creator (4.5.1).