Measure test coverage for files in custom programming language that is translated to C/C++?

Question

I have code in a domain-specific language (DSL). Files in this language are translated into C source code files, which are then compiled into binaries by a usual compiler toolchain (GCC):

DSL file --> C file --> Object file --> binary file

I want to measure test coverage for code written in this DSL. The language lacks native tooling support for measuring test coverage. However, I can use traditional GCC tools such as gcov and compiler's --coverage flags (or Clang equivalents) to instrument the generated binaries. The intermediate C-representation can then be annotated with coverage information.

DSL file --> C file --> Instrumented object file --> instrumented binary file --> coverage database
                ↕                                                                     |
         annotated C file <-----------------------------------------------------------+

The problem is, the intermediate C-code does not precisely map to its DSL input: symbols may be renamed, methods moved around, lines added and removed etc.

It is quite hard to mentally map the source code lines back and forth.

Is there a way to trace back collected coverage information to associate it with the original DSL code?

Grigory Rechistov · Accepted Answer · 2022-03-10 10:14:04Z

It turns out that gcovr (and I assume gcov which it wraps does it as well) understands #line preprocessor directives. This directive informs that code lines following it should be treated as if they came from a differently named source file and were placed at different line number.

So as long as my DSL-to-C translator is capable to annotate the generated code with #lines as shown below, the coverage tools are capable of associating the coverage database with the original DSL code:

#line 3248 "foo-controller-dsl.c"
/* get_allowed_deadline */
static uint64 _dsl_M_get_allowed_deadline(foo_controller_t *_dev, obj_t *cpu)
#line 179 "/src/foo-controller/foo-controller.dsl"
{
    #line 180 "/src/foo-controller/foo-controller.dsl"
    uint64 v618_baz_freq  = _dsl_M_ctr_storage__get_ref_freq(_dev);
    #line 181 "/src/foo-controller/foo-controller.dsl"
    double v618_threshold_seconds  = _dsl_M_get_threshold_in_seconds(_dev, cpu);
    #line 182 "/src/foo-controller/foo-controller.dsl"
    double v618_threshold_baz_units  = v618_threshold_seconds * (double )v618_baz_freq;
    #line 184 "/src/foo-controller/foo-controller.dsl"
    double v618_baz_counter  = _dsl_M_ctr_storage__get_ctr(_dev);
    #line 185 "/src/foo-controller/foo-controller.dsl"
    double v618_allowed_deadline  = v618_baz_counter + v618_threshold_baz_units;
    #line 187 "/src/foo-controller/foo-controller.dsl"
    return (uint64 )((int64 )v618_allowed_deadline);
    #line 188 "/src/foo-controller/foo-controller.dsl"
}

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