STM32F103 bxCAN not working
TxMailbox -> &amp;TxMailbox. 

The manual:


  pTxMailbox  pointer to a variable where the function will return the TxMailbox used to store the Tx message. 


Since the function will apparently try to return data through this pointer, it will crash and burn if you provide a uint32_t by value.

Notably, a conforming C compiler must give you a message (warning or error) for this code. If you didn't get any such message, your tool chain is broken. References.