Add C to Rust example

c-to-rust/Cargo.toml

@@ -0,0 +1,8 @@
+[package]
+name = "c-to-rust"
+version = "0.1.0"
+authors = ["Alex Crichton <alex@alexcrichton.com>"]
+
+[lib]
+name = "double_input"
+crate-type = ["staticlib"]

c-to-rust/Makefile

@@ -0,0 +1,18 @@
+all: target/double
+	target/double
+
+target:
+	mkdir -p $@
+
+target/double: target/main.o target/libdouble_input.a
+	$(CC) -o $@ -Wl,--gc-sections $^ -lpthread
+
+target/libdouble_input.a: src/lib.rs Cargo.toml
+	cargo build
+	(cd target && ln -nsf debug/libdouble_input-*.a libdouble_input.a)
+
+target/main.o: src/main.c | target
+	$(CC) -o $@ -c $<
+
+clean:
+	rm -rf target

c-to-rust/src/lib.rs

@@ -0,0 +1,6 @@
+#![crate_type = "staticlib"]
+
+#[no_mangle]
+pub extern fn double_input(input: i32) -> i32 {
+    input * 2
+}

c-to-rust/src/main.c

@@ -0,0 +1,11 @@
+#include <stdint.h>
+#include <stdio.h>
+
+extern int32_t double_input(int32_t input);
+
+int main() {
+    int input = 4;
+    int output = double_input(input);
+    printf("%d * 2 = %d\n", input, output);
+    return 0;
+}