Compile a C library while setting custom defines

Author: eduairet

build_time_tooling/build.rs

@@ -5,4 +5,14 @@ fn main() {
         .cpp(true)
         .file("src/foo.cpp")
         .compile("foo");
+
+    cc::Build::new()
+        .define("APP_NAME", "\"bar\"")
+        .define(
+            "VERSION",
+            format!("\"{}\"", env!("CARGO_PKG_VERSION")).as_str(),
+        )
+        .define("WELCOME", None)
+        .file("src/bar.c")
+        .compile("bar");
 }

build_time_tooling/src/bar.c

@@ -0,0 +1,8 @@
+#include <stdio.h>
+
+void print_app_info() {
+#ifdef WELCOME
+    printf("Welcome to ");
+#endif
+    printf("%s - version %s\n", APP_NAME, VERSION);
+}

build_time_tooling/src/main.rs

@@ -21,6 +21,7 @@ extern "C" {
     fn hello();
     fn greet(name: *const c_char);
     fn multiply(x: i32, y: i32) -> i32;
+    fn print_app_info();
 }
 
 fn main() -> Result<()> {
@@ -31,5 +32,8 @@ fn main() -> Result<()> {
     unsafe {
         println!("{}", multiply(5, 7));
     }
+    unsafe {
+        print_app_info();
+    }
     Ok(())
 }