Unclear which functions are not interpreted

[podhrmic]

When running cn test ... on various OpenSUT code, I often get the following error:

root@ac94c45769b6:/work/components/mission_protection_system/src# cn test --output-dir=test -I include --include=include/wars.h --magic-comment-char-dollar components/instrumentation_common.c
include/common.h:34:24: warning: experimental keyword 'cn_function' (use of experimental features is discouraged)
uint8_t c_NINSTR() /*$ cn_function NINSTR; $*/ { return NINSTR; }
                       ^~~~~~~~~~~ 
...
cn: internal error, uncaught exception:
    Failure("Uninterpreted CN functions not supported at runtime. Please provide a concrete function definition")
    Raised at Stdlib.failwith in file "stdlib.ml", line 29, characters 17-33
    Called from Cn__Cn_internal_to_ail.cn_to_ail_function_internal in file "backend/cn/lib/cn_internal_to_ail.ml", lines 2952-2954, characters 6-29
    Called from Stdlib__List.map in file "list.ml", line 86, characters 15-19
    Called from Cn__Executable_spec_internal.generate_c_functions_internal in file "backend/cn/lib/executable_spec_internal.ml", lines 376-382, characters 4-24
    Called from Cn__Executable_spec.main in file "backend/cn/lib/executable_spec.ml", line 233, characters 4-63
    Called from Dune__exe__Main.run_tests.(fun) in file "backend/cn/bin/main.ml", lines 495-504, characters 10-26
    Called from Cerb_colour.without_colour in file "util/cerb_colour.ml", line 40, characters 10-13
    Called from Dune__exe__Main.run_tests.(fun) in file "backend/cn/bin/main.ml", lines 476-531, characters 6-10
    Called from Dune__exe__Main.with_well_formedness_check in file "backend/cn/bin/main.ml", lines 157-168, characters 6-48
    Re-raised at Dune__exe__Main.with_well_formedness_check in file "backend/cn/bin/main.ml", line 176, characters 4-69
    Called from Cmdliner_term.app.(fun) in file "cmdliner_term.ml", line 24, characters 19-24
    Called from Cmdliner_eval.run_parser in file "cmdliner_eval.ml", line 35, characters 37-44

The source code hides certain functions/features to make cn verify pass, but it is difficult for me to understand which functions are causing the problems for cn test. I tried removing all modifications, but I am still hitting the same error. Is it possible to add a more informative output, ideally pointing at the offending line in the C source?

[podhrmic]

@ZippeyKeys12 this issue is important for debugging - the OpenSUT code contains lot of #ifdef CN_ENV to help the verification pass, but testing might need a different set of #ifdef CN_TEST macros. So a more informative output would be very helpful