scantailor fails to build with clang-3.4 due to friend declaration bugs

[ryandesign (Ryan Carsten Schmidt)]

Jeremy asked in r102283 how scantailor failed to build with clang. This ticket is to document that failure. The attached log is from Xcode 4.6 on OS X 10.8.2 Mountain Lion.

In file included from /opt/local/var/macports/build/_Users_rschmidt_macports_dports_graphics_scantailor/scantailor/work/scantailor-0.9.11.1/dewarping/DistortionModelBuilder.cpp:21:
In file included from /opt/local/var/macports/build/_Users_rschmidt_macports_dports_graphics_scantailor/scantailor/work/scantailor-0.9.11.1/dewarping/CylindricalSurfaceDewarper.h:22:
In file included from /opt/local/var/macports/build/_Users_rschmidt_macports_dports_graphics_scantailor/scantailor/work/scantailor-0.9.11.1/math/HomographicTransform.h:23:
/opt/local/var/macports/build/_Users_rschmidt_macports_dports_graphics_scantailor/scantailor/work/scantailor-0.9.11.1/math/MatrixCalc.h:127:10: error: calling a private constructor of class 'mcalc::Mat<double>'
                return mcalc::Mat<T>(&m_alloc, data, rows, cols);
                       ^
/opt/local/var/macports/build/_Users_rschmidt_macports_dports_graphics_scantailor/scantailor/work/scantailor-0.9.11.1/dewarping/DistortionModelBuilder.cpp:516:5: note: in instantiation of member function 'MatrixCalc<double, mcalc::DynamicPoolAllocator<double> >::operator()' requested here
                mc(&At[0], 2, polyline_size).transWrite(&A[0]);
                  ^
/opt/local/var/macports/build/_Users_rschmidt_macports_dports_graphics_scantailor/scantailor/work/scantailor-0.9.11.1/math/MatrixCalc.h:107:2: note: declared private here
        Mat(AbstractAllocator<T>* alloc, T const* data, int rows, int cols)
        ^
1 error generated.

[jeremyhu (Jeremy Huddleston Sequoia)]

Ok, then this looks like a project bug. Those should probably not be private.

[raphael-st (Raphael Straub)]

Replying to jeremyhu@…:

Ok, then this looks like a project bug. Those should probably not be private.

But, there is a friend declaration in class Mat in math/MatrixCalc.h:

template<typename T>
class Mat
{
        template<typename OT, typename Alloc> friend class MatrixCalc;
        [...]
private:
        Mat(AbstractAllocator<T>* alloc, T const* data, int rows, int cols)
                : alloc(alloc), data(data), rows(rows), cols(cols) {}
        [...]
};
[...]
template<typename T, typename Alloc = mcalc::StaticPoolAllocator<T, 128, 9> >
class MatrixCalc
{
        [...]
public:
        MatrixCalc() {}

        mcalc::Mat<T> operator()(T const* data, int rows, int cols) {
                return mcalc::Mat<T>(&m_alloc, data, rows, cols);
        }
        [...]
};

This looks OK to me and also to gcc. Is this one of the ​bugs concerning friend declarations in clang?

[Martin.vGagern@…]

See also #46014: macports-clang-3.4 causes this failure as well.

[jeremyhu (Jeremy Huddleston Sequoia)]

Could you please attach preprocessed source for the failing DistortionModelBuilder.cpp?

[Martin.vGagern@…]

Upstream commit ​123a71a has a fix. The problem is the namespace: Mat is in the mcalc namespace while MatrixCalc is in the global namespace, so the friend declaration should go ::MatrixCalc. I managed to successfully build the current upstream master (​6475756) using Apple LLVM version 5.1 (clang-503.0.38) (based on LLVM 3.4svn).

[jeremyhu (Jeremy Huddleston Sequoia)]

Ah, ok. thanks. I was heading back to thinking this was a compiler bug, but I'm glad to see it is a project bug and with a fix too! qt4-mac is in the middle of compile here, but I suspect it'll finish up sometime tomorrow to allow me to test the change and commit if someone else doesn't beat me to it.

[jeremyhu (Jeremy Huddleston Sequoia)]

r128696