Can't say for all, but I am reasonably certain C++ does not support designated initializers/sparse array definitions. Some of these features where added in more recent revisions to the C specification from which C++ has diverged from. I would expect most of the differences would become more pronounced starting with C99.

In theory, C++20 has designated init, but it has so many restrictions compared to C99 that it is pretty much useless for real world code.