From e22236f201613d3e4864b4ca8af386321ec9cc7d Mon Sep 17 00:00:00 2001
From: Jaroslaw Konik <konikjar@gmail.com>
Date: Tue, 27 May 2025 18:58:02 +0200
Subject: [PATCH] dynamic resolutions docs

---
 Cargo.toml                    |  1 +
 book/src/ruby/installation.md | 10 ++++++++++
 src/lib.rs                    | 30 ++++++++++++++++++++++++++++++
 src/runtimes/ruby.rs          |  4 ++++
 4 files changed, 45 insertions(+)

diff --git a/Cargo.toml b/Cargo.toml
index 10f089d..ad3fc0f 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -34,6 +34,7 @@ mlua = { version = "0.9.8", features = [
 magnus = { version = "0.7.1", optional = true }
 rb-sys = { version = "*", default-features = false, features = ["link-ruby", "ruby-static"], optional = true }
 crossbeam-channel = "0.5.15"
+libc = "0.2.172"
 
 [[example]]
 name = "call_function_from_rust_rhai"
diff --git a/book/src/ruby/installation.md b/book/src/ruby/installation.md
index 40f291e..1dc0a82 100644
--- a/book/src/ruby/installation.md
+++ b/book/src/ruby/installation.md
@@ -38,3 +38,13 @@ bevy_scriptum = { version = "0.8", features = ["ruby"] }
 
 If you need a different version of bevy you need to use a matching bevy_scriptum
 version according to the [bevy support matrix](../bevy_support_matrix.md)
+
+Ruby also needs dynamic symbol resolution and since `bevy_scriptum` links Ruby
+statically the following `build.rs` file is needed to be present in project
+root directory.
+
+```rust
+fn main() {
+    println!("cargo:rustc-link-arg=-rdynamic");
+}
+```
diff --git a/src/lib.rs b/src/lib.rs
index 0e83be6..94bad40 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -371,6 +371,10 @@ pub trait Runtime: Resource + Default {
         context: &Self::CallContext,
         args: Vec<Self::Value>,
     ) -> Result<Self::Value, ScriptingError>;
+
+    fn needs_rdynamic_linking() -> bool {
+        false
+    }
 }
 
 pub trait FuncArgs<'a, V, R: Runtime> {
@@ -433,6 +437,19 @@ impl BuildScriptingRuntime for App {
     /// Adds a scripting runtime. Registers required bevy systems that take
     /// care of processing and running the scripts.
     fn add_scripting<R: Runtime>(&mut self, f: impl Fn(ScriptingRuntimeBuilder<R>)) -> &mut Self {
+        #[cfg(debug_assertions)]
+        if R::needs_rdynamic_linking() {
+            if !is_rdynamic_linking() {
+                panic!(
+                    "Missing `-rdynamic`: symbol resolution failed.\n\
+                     It is needed by {:?}.\n\
+                     Please add `println!(\"cargo:rustc-link-arg=-rdynamic\");` to your build.rs\n\
+                     or set `RUSTFLAGS=\"-C link-arg=-rdynamic\"`.",
+                    std::any::type_name::<R>()
+                );
+            }
+        }
+
         self.world_mut()
             .resource_mut::<MainScheduleOrder>()
             .insert_after(Update, R::Schedule::default());
@@ -495,6 +512,19 @@ impl<R: Runtime> Default for Callbacks<R> {
     }
 }
 
+pub extern "C" fn is_rdynamic_linking() -> bool {
+    unsafe {
+        // Get a function pointer to itself
+        let addr = is_rdynamic_linking as *const libc::c_void;
+        let mut info: libc::Dl_info = std::mem::zeroed();
+
+        // Try to resolve symbol info
+        let result = libc::dladdr(addr, &mut info);
+
+        result != 0 && !info.dli_sname.is_null()
+    }
+}
+
 pub mod prelude {
     pub use crate::{BuildScriptingRuntime as _, Runtime as _, Script};
 }
diff --git a/src/runtimes/ruby.rs b/src/runtimes/ruby.rs
index b41262e..1ccccdd 100644
--- a/src/runtimes/ruby.rs
+++ b/src/runtimes/ruby.rs
@@ -505,6 +505,10 @@ impl Runtime for RubyRuntime {
             Ok(RubyValue::new(result))
         })
     }
+
+    fn needs_rdynamic_linking() -> bool {
+        true
+    }
 }
 
 pub mod magnus {