Do you get to the interview, or they don't even reply to your resume? Because if you get interviews you need interview practice not projects.

Assuming you do have, like, school projects, and your PhD project includes programming. Otherwise you do need projects. For C++ a good way to have projects is to talk to PhD students in other fields (physics and bio are good) and ask if they need help with their computation and modeling. Listen to them a lot as they often already use software for most important things but may have need of e.g. quickly indexing text files or targeted data visualizations. In industry, we like hearing about collaborative projects.