Using C++ std::exceptions with NCS

[OliverB]

Hi,

we're using a library which is written in C++ and is using exceptions. As stated here Zephyr has C++ support including exceptions.

Following the docs I set

...
CONFIG_CPLUSPLUS=y
CONFIG_LIB_CPLUSPLUS=y

CONFIG_NEWLIB_LIBC=y
CONFIG_EXCEPTIONS=y
CONFIG_NEWLIB_LIBC_NANO=n
...

But this leads to a linker error:

fini.c:(.text.__libc_fini_array+0x20): undefined reference to `_fini' 

When removing 

CONFIG_NEWLIB_LIBC_NANO=n

the code is being compiled with a warning that CONFIG_EXCEPTIONS is set to 'n' because of unsatisfied dependencies (!NEWLIB_LIBC_NANO). In this case thrown exceptions are not catched. Instead of running the catch-path the code is running into _exit in libc-hooks.c which is part of newlib. 

So, does anybody know how to enable the exception support? Am I missing some more CONFIGs?

Regards,
Oliver

[Øyvind]

Hello Oliver, 

This is unfortunately nothing we can assist with as this is part of the Zephyr RTOS. Please reach out to the Zephyr community through their Discord channel.

Kind regards,
Øyvind

[OliverB]

Hi Øyvind,

thanks for your suggestion. It's definitely a good place to get Zephyr related help.

For those that might run into the same issue, here's my solution:

In prj.conf you need the C++ and exceptions related stuff:

...
CONFIG_CPLUSPLUS=y
CONFIG_LIB_CPLUSPLUS=y

CONFIG_NEWLIB_LIBC=y
CONFIG_EXCEPTIONS=y
CONFIG_NEWLIB_LIBC_NANO=n
...

To prevent the linker error, I had to implement following function:

void exit(int reason) {
  printk("EXIT %d", reason);
  while (1)
    ;
}

Now the code compiles without error and the exceptions are being catched. But Interestingly exit() is being called.