This problem appears when main.c is changed to main.cpp and error is reported in file “startup_stm32f411ceux.s�? bl main (simply, main.cpp is ignored) Also it appears randomly (on/off) when creating a new project from File→New→STM32 Project from an...

If you want to use cpp, do not forget to select cpp when using STM32CubeMX for the Target Languge. If you forget to select cpp and rename main.c to main.cpp , then you will get "bl main" error.Miguel