6 years, 4 months ago.

Explicit interrupt handler attach required in C++, but not C? (Nucleo-32F042)

I'm working with a UART console in MBED OS2 using STMicro's HAL libraries as opposed to the MBED Serial class. I could not get receive to work(the RX handler was not getting called, and further evidence showed that the program was going "in the weeds" on a receive character. I decided to make a small test program just to echo characters received, all in one main.c file. It works, however, if I change just the name of the file to main.cpp, RX stops working. After a lot of trial and error I found that adding this:

NVIC_SetVector(USART2_IRQn, (uint32_t)&USART2_IRQHandler); Attach interrupt handler

to the init code then fixed the RX operation. I thought USART2_IRQHandler, was a default predefined handler(somewhere in the STM32 HAL). Why do I get the attach for "free" in C, but in C++, I'm required to call NVIC_SetVector? This may be a STM HAL specific thing but I thought I'd post it here to see if anyone knew the "why" and so anyone else having this issue would have something to try that worked for me...