> It's in many cases as simple as renaming a file from .c to .cpp.

That is rather optimistic, but, for example, scpptool has a feature [1] that auto-converts from C to a subset of C that can (hopefully) be compiled with clang++. If the original C source uses C11 extensions, clang++ seems to generally produce warnings rather than compile errors.

> But for writing something from scratch it's better to use Rust.

scpptool attempts to make C++ a more viable option by enforcing a memory and data race safe subset using a similar safety strategy.

[1] https://github.com/duneroadrunner/SaferCPlusPlus-AutoTransla...