How to make C++ wait after emitting signal

Hi everyone I have an app that reads data from a serial port. On a certain message type the C++ emits a signal that is handled by QML. I want to make the C++ code wait until the signal has been serviced. I use signals here, but I’d prefer a function and return value. I’m not sure how I’d go about this without hacking the mother out of it and I would like it elegant. Has anyone done this before? I appreciate any help Thanks