From 57499cf8b3add216dde930df626ab7828364eff9 Mon Sep 17 00:00:00 2001
From: James Wainwright <james.wainwright@lowrisc.org>
Date: Tue, 16 Jul 2024 11:20:26 +0100
Subject: [PATCH] Add shared-header bindgen example

---
 examples/bindgen/BUILD.bazel            | 21 ++++++++++++++-
 examples/bindgen/shared.rs              |  4 +++
 examples/bindgen/shared/BUILD.bazel     | 36 +++++++++++++++++++++++++
 examples/bindgen/shared/greeting.h      |  6 +++++
 examples/bindgen/shared/hello.c         |  6 +++++
 examples/bindgen/shared/hello.h         |  6 +++++
 examples/bindgen/shared/hello.rs        |  6 +++++
 examples/bindgen/{main.rs => simple.rs} |  0
 8 files changed, 84 insertions(+), 1 deletion(-)
 create mode 100644 examples/bindgen/shared.rs
 create mode 100644 examples/bindgen/shared/BUILD.bazel
 create mode 100644 examples/bindgen/shared/greeting.h
 create mode 100644 examples/bindgen/shared/hello.c
 create mode 100644 examples/bindgen/shared/hello.h
 create mode 100644 examples/bindgen/shared/hello.rs
 rename examples/bindgen/{main.rs => simple.rs} (100%)

diff --git a/examples/bindgen/BUILD.bazel b/examples/bindgen/BUILD.bazel
index 400fd0c0fa..d2202151ca 100644
--- a/examples/bindgen/BUILD.bazel
+++ b/examples/bindgen/BUILD.bazel
@@ -14,7 +14,7 @@ rust_bindgen_library(
 
 rust_binary(
     name = "simple_example",
-    srcs = ["main.rs"],
+    srcs = ["simple.rs"],
     deps = [":simple_bindgen"],
 )
 
@@ -22,3 +22,22 @@ rust_test(
     name = "simple_test",
     crate = ":simple_example",
 )
+
+rust_bindgen_library(
+    name = "hello_c_bindgen",
+    bindgen_flags = [
+        "--allowlist-function=hello",
+    ],
+    cc_lib = "//bindgen/shared:hello_c",
+    crate_name = "hello_c",
+    header = "//bindgen/shared:hello.h",
+)
+
+rust_binary(
+    name = "shared_example",
+    srcs = ["shared.rs"],
+    deps = [
+        ":hello_c_bindgen",
+        "//bindgen/shared:hello_rs",
+    ],
+)
diff --git a/examples/bindgen/shared.rs b/examples/bindgen/shared.rs
new file mode 100644
index 0000000000..784a42aeb5
--- /dev/null
+++ b/examples/bindgen/shared.rs
@@ -0,0 +1,4 @@
+fn main() {
+    hello_rs::hello();
+    unsafe { hello_c::hello() };
+}
diff --git a/examples/bindgen/shared/BUILD.bazel b/examples/bindgen/shared/BUILD.bazel
new file mode 100644
index 0000000000..f7b471b660
--- /dev/null
+++ b/examples/bindgen/shared/BUILD.bazel
@@ -0,0 +1,36 @@
+load("@rules_cc//cc:defs.bzl", "cc_library")
+load("@rules_rust//bindgen:defs.bzl", "rust_bindgen")
+load("@rules_rust//rust:defs.bzl", "rust_library")
+
+package(default_visibility = ["//bindgen:__pkg__"])
+
+cc_library(
+    name = "greeting",
+    hdrs = ["greeting.h"],
+)
+
+rust_bindgen(
+    name = "greeting_bindgen",
+    bindgen_flags = [
+        "--allowlist-var=GREETING",
+        "--generate-cstr",
+    ],
+    cc_lib = ":greeting",
+    header = "greeting.h",
+)
+
+rust_library(
+    name = "hello_rs",
+    srcs = [
+        "hello.rs",
+        ":greeting_bindgen",
+    ],
+    crate_root = "hello.rs",
+)
+
+cc_library(
+    name = "hello_c",
+    srcs = ["hello.c"],
+    hdrs = ["hello.h"],
+    deps = [":greeting"],
+)
diff --git a/examples/bindgen/shared/greeting.h b/examples/bindgen/shared/greeting.h
new file mode 100644
index 0000000000..7cfaf8f0fb
--- /dev/null
+++ b/examples/bindgen/shared/greeting.h
@@ -0,0 +1,6 @@
+#ifndef __FFI_H_INCLUDE__
+#define __FFI_H_INCLUDE__
+
+#define GREETING "Hello"
+
+#endif // __FFI_H_INCLUDE__
diff --git a/examples/bindgen/shared/hello.c b/examples/bindgen/shared/hello.c
new file mode 100644
index 0000000000..0614aa7ae0
--- /dev/null
+++ b/examples/bindgen/shared/hello.c
@@ -0,0 +1,6 @@
+#include <stdio.h>
+#include "greeting.h"
+
+void hello(void) {
+  printf("%s from C!\n", GREETING);
+}
diff --git a/examples/bindgen/shared/hello.h b/examples/bindgen/shared/hello.h
new file mode 100644
index 0000000000..2ed0544293
--- /dev/null
+++ b/examples/bindgen/shared/hello.h
@@ -0,0 +1,6 @@
+#ifndef HELLO_H_INCLUDE__
+#define HELLO_H_INCLUDE__
+
+void hello(void);
+
+#endif // HELLO_H_INCLUDE__
diff --git a/examples/bindgen/shared/hello.rs b/examples/bindgen/shared/hello.rs
new file mode 100644
index 0000000000..2090f88fc1
--- /dev/null
+++ b/examples/bindgen/shared/hello.rs
@@ -0,0 +1,6 @@
+mod greeting_bindgen;
+
+pub fn hello() {
+    let greeting = greeting_bindgen::GREETING.to_str().unwrap();
+    println!("{greeting} from Rust!");
+}
diff --git a/examples/bindgen/main.rs b/examples/bindgen/simple.rs
similarity index 100%
rename from examples/bindgen/main.rs
rename to examples/bindgen/simple.rs