My program keeps crashing. My compiler doesn't give any error, message or anything else

I am working on a program. I tested it (no errors, worked perfectly), went on a break, and when I returned I was greeted with weird errors. When I fixed them, the program started crashing immediately after it was opened. Because my debugger/compiler didn't give any clues on what is happening, I went through my code and tested it with a printf every paragraph or so, to see where it stops working. I eventually found where it didn't print anymore, but changing the code, replacing everything in if (things) with true didn't do the job, since the place where it failed kept shifting. I had a backup from the previous day, where I am absolutely sure it works and has no errors, but after compiling it and running the .exe, it crashed upon opening too. This makes me think it's something to do with my compiler.The text editor I use is Emacs and the compiler is MSYS2 64x. The programming language is C++.What is going on?