avr-gcc: Undefined references to __iob from unity.c

[davidrea]

It seems that the avr-gcc header files inject references to the __iob input/output buffer symbol, so attempting to mock any avr-gcc module with #include <avr/io.h> will cause the following linker errors:

<<snip>>
Compiling mock_io_manager.c...
Linking test_stateMachine_interface.out...
/usr/bin/ld: build/test/out/c/unity.o: in function `UnityPrintChar':
/var/lib/gems/2.7.0/gems/ceedling-0.30.0/vendor/unity/src/unity.c:84: undefined reference to `__iob'
/usr/bin/ld: /var/lib/gems/2.7.0/gems/ceedling-0.30.0/vendor/unity/src/unity.c:89: undefined reference to `__iob'
/usr/bin/ld: /var/lib/gems/2.7.0/gems/ceedling-0.30.0/vendor/unity/src/unity.c:90: undefined reference to `__iob'
/usr/bin/ld: /var/lib/gems/2.7.0/gems/ceedling-0.30.0/vendor/unity/src/unity.c:95: undefined reference to `__iob'
/usr/bin/ld: /var/lib/gems/2.7.0/gems/ceedling-0.30.0/vendor/unity/src/unity.c:96: undefined reference to `__iob'
/usr/bin/ld: build/test/out/c/unity.o:/var/lib/gems/2.7.0/gems/ceedling-0.30.0/vendor/unity/src/unity.c:101: more undefined references to `__iob' follow
collect2: error: ld returned 1 exit status

@stephendpmurphy also ran into this problem in tiny.oled-firmware #13 but that issue remains unsolved...

My first thought on a workaround was to include a dummy __iob object (or maybe a re-redirect back to standard host OS streams) in a source file within test/support/ for the linker to resolve, but I'm not sure where to start.

[mvandervoord]

Any non-standard compiler-specific defines like this can usually be avoided by adding the following to your cmock configuration:

:cmock:
   :strippables:
      - __iob

These values will then be stripped from the file before it is parsed for function prototypes.

[davidrea]

Awesome - will give it a try!!

[davidrea]

Hmm...no dice...still getting the undefined reference errors at the link stage. Tried running ceedling clobber beforehand too, just to make sure we started fresh.

Also tried while using the fake_function_framework plugin, same results.

[mvandervoord]

Hm. I hadn't noticed that the problem is in the linker step. strippables is only going to help during mocking.

It's strange that it's citing unity as the thing that contains __iob. I notice that you're on an older ceedling... but honestly I don't recall that ever being part of unity? If you search unity.cpp or its header files for that, does it show up?