subchroma_image_view methods return reference to local temporary object

[mloskot]

Actual behavior

../../boost/gil/extension/toolbox/image_types/subchroma_image.hpp:248:49: warning: returning reference to local temporary object [-Wreturn-stack-address]
    const point_t& v_ssfactors() const { return point_t( get_deref_fn().vx_ssfactor(), get_deref_fn().vx_ssfactor() ); }
                                                ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

../../boost/gil/extension/toolbox/image_types/subchroma_image.hpp:249:49: warning: returning reference to local temporary object [-Wreturn-stack-address]
    const point_t& u_ssfactors() const { return point_t( get_deref_fn().ux_ssfactor(), get_deref_fn().ux_ssfactor() ); }
                                                ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Expected behavior

C++ Minimal Working Example

$ cat test.cpp
#include <boost/gil/extension/toolbox//image_types/subchroma_image.hpp>
int main() {}

$ clang++-10 -std=c++11 -I/mnt/d/boost.wsl test.cpp

Environment

• Version (Git ref or <boost/version.hpp>): 1.72 and current develop branch
• Compiler: clang 3.9, 6, 7, ...

[Scramjet911]

Is this still an issue? I couldn't reproduce it on g++ 9.3 and c++11, all warnings enabled.

[mloskot]

Is this still an issue?

The code in question has not changed.

I couldn't reproduce it on g++ 9.3

As given in the issue description, I reproduced it with clang.

[sdebionne]

Isn't the fix as simple as returning by value instead of by reference?