Add example for cpp calling rust by including header

examples/ffi/cpp_calling_rust_with_header/BUILD

@@ -0,0 +1,7 @@
+load("@rules_cc//cc:defs.bzl", "cc_library")
+
+cc_library(
+    name = "main",
+    srcs = ["main.cpp"],
+    deps = ["//ffi/cpp_calling_rust_with_header/rust:librusty_for_cc"],
+)

examples/ffi/cpp_calling_rust_with_header/main.cpp

@@ -0,0 +1,6 @@
+#include "rusty.h"
+
+int main() {
+  print_c_hello_rust();
+  return 0;
+}

examples/ffi/cpp_calling_rust_with_header/rust/BUILD

@@ -0,0 +1,17 @@
+load("@rules_cc//cc:defs.bzl", "cc_import")
+load("@rules_rust//rust:defs.bzl", "rust_static_library")
+
+rust_static_library(
+    name = "librusty",
+    srcs = ["librusty.rs"],
+    crate_name = "rusty",
+    visibility = ["//visibility:public"],
+)
+
+cc_import(
+    name = "librusty_for_cc",
+    hdrs = ["rusty.h"],
+    includes = [package_name()],
+    static_library = ":librusty",
+    visibility = ["//visibility:public"],
+)

examples/ffi/cpp_calling_rust_with_header/rust/librusty.rs

@@ -0,0 +1,6 @@
+//! A simple hello world example that can be called from C
+
+#[no_mangle]
+pub fn print_c_hello_rust() {
+    println!("Hello Rust!");
+}

examples/ffi/cpp_calling_rust_with_header/rust/rusty.h

@@ -0,0 +1,6 @@
+#ifndef SIMPLE_PRINTER_H
+#define SIMPLE_PRINTER_H
+
+extern "C" void print_c_hello_rust();
+
+#endif