An example of how to pass closures through FFI to C functions. The principle is
that if you have a C function that accepts a function pointer like a void (*)(void *), and an argument like a void *, then you can convert a reference
to the closure to a void * and pass in a shim function pointer that will
convert it back and call it.
Also note that if the closure is stored anywhere else and then invoked later,
the reference would be invalid. In this case, we use a Box; see the
c_deferred_call/c_do_deferred_call example.
# Compile only the C parts (make the shared library)
$ make cparts
# Compile everything (C + Rust)
$ make
# Run the program
$ make run
# Remove all build output
$ make clean
Requires make, a C and Rust toolchain, and libclang (for bindgen). You may need
to set LIBCLANG_PATH to the location of the libclang installation.
Nix is provided to set up a dev shell with the required dependencies and environment variables.