C++ 20 compilation issue in rawtoaces_util/image_converter.cpp

[jfpanisset]

When compiling rawtoaces_util/image_converter.cpp with gcc 14 in C++ 20 mode, the following code fails:

#9 38.14 /opt/conan_home/d/b/rawtoe81215628ac43/b/src/src/rawtoaces_util/image_converter.cpp: In function 'rta::util::CameraIdentifier rta::util::get_camera_identifier(const OpenImageIO::v3_1
::ImageSpec&, const ImageConverter::Settings&)':
#9 38.14 /opt/conan_home/d/b/rawtoe81215628ac43/b/src/src/rawtoaces_util/image_converter.cpp:212:40: error: could not convert '{camera_make, camera_model}' from '<brace-enclosed initializer l
ist>' to 'rta::util::CameraIdentifier'
#9 38.14   212 |     return { camera_make, camera_model };
#9 38.14       |                                        ^
#9 38.14       |                                        |
#9 38.14       |                                        <brace-enclosed initializer list>

In C++ 20 used defined constructors prevent a class from being considered as an aggregate:

https://en.cppreference.com/w/cpp/20.html
https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/p1008r1.pdf

The following patch against versions 2.0.0 allows the file to compile, but I have not tested it (yet) against earlier C++ versions:

--- src/rawtoaces_util/image_converter.cpp
+++ src/rawtoaces_util/image_converter.cpp
@@ -22,7 +22,8 @@
     std::string make;
     std::string model;

-    CameraIdentifier() = default;
+    // In C++ 20 a default constructure means the class is no longer an aggregate
+    // CameraIdentifier() = default;

     bool is_empty() const { return make.empty() && model.empty(); }

[antond-weta]

Thanks JF,

I've fixed the issue and also added some C++20 runners on CI #253