From 64bd331314362d93b43e8df40e0ecd70ad9ba22c Mon Sep 17 00:00:00 2001
From: Martin Geisler <mgeisler@google.com>
Date: Mon, 16 Dec 2024 22:53:54 +0100
Subject: [PATCH] Add speaker notes to interop with C slides (#2496)

Part of #1083.
---
 src/android/interoperability.md        | 12 ++++++++++++
 src/android/interoperability/with-c.md | 14 ++++++++++++++
 2 files changed, 26 insertions(+)

diff --git a/src/android/interoperability.md b/src/android/interoperability.md
index 9436af43..8c116d2a 100644
--- a/src/android/interoperability.md
+++ b/src/android/interoperability.md
@@ -8,3 +8,15 @@ that you can:
 
 When you call functions in a foreign language we say that you're using a
 _foreign function interface_, also known as FFI.
+
+<details>
+
+- This is a key ability of Rust: compiled code becomes indistinguishable from
+  compiled C or C++ code.
+
+- Technically, we say that Rust can be compiled to the same [ABI] (application
+  binary interface) as C code.
+
+</details>
+
+[ABI]: https://en.wikipedia.org/wiki/Application_binary_interface
diff --git a/src/android/interoperability/with-c.md b/src/android/interoperability/with-c.md
index ad631e66..9991420a 100644
--- a/src/android/interoperability/with-c.md
+++ b/src/android/interoperability/with-c.md
@@ -24,3 +24,17 @@ We already saw this in the
 > production.
 
 We will look at better options next.
+
+<details>
+
+- The [`"C"` part][extern-abi] of the `extern` block tells Rust that `abs` can
+  be called using the C [ABI] (application binary interface).
+
+- The `safe fn abs` part tells that Rust that `abs` is a safe function. By
+  default, extern functions are considered unsafe, but since `abs(x)` is valid
+  for any `x`, we can declare it safe.
+
+</details>
+
+[extern-abi]: https://doc.rust-lang.org/reference/items/external-blocks.html#abi
+[ABI]: https://en.wikipedia.org/wiki/Application_binary_interface