Actually C++ is not slower or more bloat than C, depending on the features used.
For example I do not use RTTI or exceptions, so that makes it about the same as C for size. Yes you have to turn these features off in your compiler (-fno-rtti, -fno-exceptions). Sure you have trampolines or jump tables for function overloading but you have to do the same in C. If you do not use inheritance or function overloading you do not have the penalty.
I find that in most of my embedded projects the cost of development time is more than the cost of the processor for 5 years of production, that is the products are not super high volume products. As such, reducing development time is very important. To this end I do things like write libraries and test them, and then reuse them. For example I write an abstract interface class for a CharDevice, and BlockDevice. Then a UART can be a CharDevice and EEPROM a BlockDevice, SDCard is a BlockDevice, etc. This allows faster development. Sure I can do this in C, but C++ basically does the same thing I would do in C and is easier to understand.
Also things like templates are valuable, for example I wrote a FIFO template. I debug that template once and never have to write fifo code again. This is something very hard to do in C with any efficiency. Now I can create a FIFO for uint8_t, uint32_t, or a structure with one line. This can not be done easy in C. The same is true for circular buffers and such...
So yea C++ on embedded is very valid and real. I have been doing professional embedded C for over 30 years and just switched to C++ and do not want to go back to C. The misconceptions about bloat are no longer valid. Sure you can write bad C++ code using standard templates and such but you can also write bad C code, so don't do either. I think the misconception about C++ is because people try to do stupid stuff like use cout, new, RTTI, exceptions, etc. Where most of the time the simple compile time features of C++ offer huge advantages over C.
At the end of the day all the compile time features of C++ are free, like classes. There is zero reason not to use them because they are free. The run time features are not free but you can choose what you use, and turn off what you don't need.
So yes I can write bad C++ code that is slow and bloated. I can write bad C code that is slow and bloated. My job is to write functional code that works and works correctly with no side effects and I can do that faster and more efficiently in C++ using OO and minimal features of C++. Maybe others can not, but that is not my problem.
Note that I have worked on projects in the past where we squeezed every clock and every byte out of a processor. However I have not had to optimize for size or speed in 10 years. That is processors are so cheap and powerful if you have to optimize code for size or speed then you most likely picked the wrong microprocessor.
The problem with interrupt handlers which I asked about still exists if you use C to write the code. That is you still have to map the interrupt handler to the correct instance of the object unless you are insane and write a driver for each UART instance, which talking about bloat and slow....
Trampas