#172 bug: branch found in member init list

[Fatman]

lcov finds a branch in the following simple constructor.

  12         [ -  + ]:         26 : Vint::Vint() : m_bytes{nullptr}, m_len{0} {}

This happens in all my constructors with member init lists.

I've narrowed it down a bit by adding whitespace:

  12                 :            : Vint::Vint() :
  13         [ -  + ]:         26 : m_bytes
  14                 :         26 : {nullptr}, m_len{0} { }

I think it's the member init list itself rather than the first member (m_bytes), because it doesn't find a branch in the second member (m_len).

=========================

OS: Ubuntu 16.04.1 LTS
lcov: LCOV version 1.12
genhtml: LCOV version 1.12
clang version 3.8.0-2ubuntu4 (tags/RELEASE_380/final)

To reproduce:

~/Vint/cmake$ clang++-3.8 test.cc Vint.cc -std=c++14 --coverage
~/Vint/cmake$ ./a.out
~/Vint/cmake$ gcov -b -color -o ./Vint.gcda ./Vint.gcno
~/Vint/cmake$ mv *.gcov cov/
~/Vint/cmake$ lcov --capture --directory . --output-file demo.info --test-name demo --rc lcov_branch_coverage=1
~/Vint/cmake$ genhtml demo.info --output-directory cov/demo --demangle-cpp --rc lcov_branch_coverage=1 --legend --prefix .

test.cc (Vint.cc and Vint.hh in attachment):

#include "Vint.hh"

#include <iostream>

using std::cout;
using std::endl;

void output(Vint temp) {
    cout << temp.val();
    cout << " => " << temp.xxd();
    cout << " (length " << temp.len() << ")";
    cout << endl;
}

int main(int, char **) {
    output(Vint{});
    output(Vint{0});
    output(Vint{127});    // 0x7f
    output(Vint{128});    // 0x0180
    output(Vint{129});    // 0x0181
    output(Vint{16383});  // 0x7fff
    output(Vint{16384});  // 0x018080
    output(Vint{16385});  // 0x018081
    output(Vint{288312}); // 0x11ccb8
    {
        Vint v{288312};
        Vint v2{v};
        Vint v3 = v;
        v2 = v3;
        cout << "v2 < v: " << std::boolalpha << (v2 < v.val()) << endl;
        cout << "v3 > v: " << std::boolalpha << (v3 > v.val()) << endl;
        cout << "v2 == v3: " << std::boolalpha << (v2 == v3) << endl;
        cout << "v == v3: " << std::boolalpha << (v == v3.val()) << endl;
        cout << "v2 <= v: " << std::boolalpha << (v2 <= v.val()) << endl;
        cout << "v3 >= v: " << std::boolalpha << (v3 >= v.val()) << endl;
    }
    {
        Vint v{288312};
        Vint v2{123};
        Vint v3{4321};
        cout << "v2 < v: " << std::boolalpha << (v2 < v.val()) << endl;
        cout << "v > v3: " << std::boolalpha << (v > v3.val()) << endl;
        cout << "v2 == v3: " << std::boolalpha << (v2 == v3) << endl;
        cout << "v == v3: " << std::boolalpha << (v == v3.val()) << endl;
        cout << "v <= v2: " << std::boolalpha << (v <= v2.val()) << endl;
        cout << "v3 >= v: " << std::boolalpha << (v3 >= v.val()) << endl;
    }
    return 0;
}

[Peter Oberparleiter]

LCOV doesn't generate branch coverage information itself - it displays the data taken from gcov. I would assume that the unexpected branch coverage data is also present in the .gcov files generated by gcov.

[Fatman]

Thanks for the quick reply Peter.

I will redirect this bug report to the Clang folks, whose implementation of gcov I'm using.

Sorry for the noise.