It's been the primary and most annoying interop issue for us when we have to integrate C++ code into our primarily C codebase (= build some pieces of our code in C++, which necessarily has to interact with at least our header files).
(Second place: differences in available GCC/clang compiler extensions between C and C++ [our software does not support Windows/MSVC], third place: differences in what casts are permitted/how they are done)
Even though you need to declare a struct for this (or other) functions to receive these fields, I feel like this is the cleanest approach. What I'm not sure about is if reference, value, or pointer is the best way to let the compiler optimize this.
Edit: struggling to find a source, though this GCC doc suggests it's C99 (but maybe that's only GCC?) - https://gcc.gnu.org/onlinedocs/gcc/Designated-Inits.html