[cfe-dev] Invalid coverage results from Clang's Source-based Code Coverage

[Michał Pszona via cfe-dev]

I'm trying to get a reliable code coverage through Clang's
Source-based Code Coverage and am heading some false negatives on
virtual inheriting classes. In particular the inheriting class'
constructor is displayed as NOT covered.

Given this code:

#include <iostream>
class Foo
{
public:
    Foo()
    {
        std::cout << "in Foo()" << std::endl;
    }
};

class Bar : virtual public Foo
{
public:
   Bar()
   {
        std::cout << "in Bar()" << std::endl;  // supposedly not covered
   };
};

int main (int argc, char* argv[])
{
    Bar b;
}

The output is, obviously:

in Foo()
in Bar()

but the Bar's constructor is reported as uncovered.


I'm folliwng the steps described on the above page ie.
1. clang++ -fprofile-instr-generate -fcoverage-mapping main.cpp
2. running the binary
3. llvm-profdata merge default.profraw -o default.profdata
4. llvm-cov-4.0 show a.out --instr-profile default.profdata

Tried clang 4.0 and 5.0 (compiled from trunk) with same effect.


Could anyone help me with this issue?
Is there a way to workaround this issue?
How can I debug it to see what's causing it?


regards,
Michał Pszona