Merge pull request #1092 from godot-rust/bugfix/wasm-registration

Remove `gensym`, fix Wasm class registration

Author: Bromeon

.github/other/deny.toml

@@ -182,18 +182,16 @@ allow = [
 # List of crates to deny
 # See also: https://github.com/RustSec/advisory-db/issues/173
 deny = [
-    # unmaintained since Feb 20 + https://github.com/noamtashma/owning-ref-unsoundness
-    { name = "owning_ref" },
-
-    # unmaintained since Jul 20, RustSec refuses to acknowledge "because author says maintained"
-    # https://togithub.com/rustsec/advisory-db/pull/891
-    { name = "im" },
-    { name = "im-rc" },
-
     # Too heavy in default setup. Can be included for api-custom etc.
     # Note: rand indirectly depends on syn via rand_chacha -> ppv-lite86 -> zerocopy -> zerocopy-derive.
-    { name = "syn", wrappers = ["bindgen", "gensym", "zerocopy-derive"] },
+    { name = "syn", wrappers = ["bindgen"] },
     { name = "serde", wrappers = ["godot-core", "serde_json"] },
+    { name = "rand" },
+
+    # Unmaintained since Jul 2020, RustSec refuses to acknowledge "because author says maintained".
+    # https://github.com/rustsec/advisory-db/pull/891
+    { name = "im" },
+    { name = "im-rc" },
 ]
 
 # List of features to allow/deny

godot-ffi/Cargo.toml

@@ -33,16 +33,14 @@ api-4-3 = ["godot-bindings/api-4-3"]
 api-4-4 = ["godot-bindings/api-4-4"]
 # ]]
 
-# TODO: get rid of gensym, which is implementable with proc-macros. Update cargo-deny.
-# gensym pulls in entire syn for 10 LoC. See https://github.com/regiontog/gensym/blob/master/src/lib.rs.
-# Might however require godot-ffi to depend on godot-macro, which is not ideal...
 [dependencies]
 
 [target.'cfg(target_os = "linux")'.dependencies]
-libc = "0.2.153"
+libc = "0.2.171"
 
 [target.'cfg(target_family = "wasm")'.dependencies]
-gensym = "0.1.1"
+# Only needed for WASM identifier generation.
+godot-macros = { path = "../godot-macros", version = "=0.2.4", features = ["experimental-wasm"] }
 
 [build-dependencies]
 godot-bindings = { path = "../godot-bindings", version = "=0.2.4" }

godot-ffi/src/interface_init.rs

@@ -16,6 +16,9 @@
 
 use crate as sys;
 
+#[cfg(not(target_family = "wasm"))]
+use crate::toolbox::read_version_string;
+
 // In WebAssembly, function references and data pointers live in different memory spaces, so trying to read the "memory"
 // at a function pointer (an index into a table) to heuristically determine which API we have (as is done below) won't work.
 #[cfg(target_family = "wasm")]
@@ -146,16 +149,3 @@ pub unsafe fn load_interface(
 ) -> sys::GDExtensionInterface {
     sys::GDExtensionInterface::load(get_proc_address)
 }
-
-fn read_version_string(version_ptr: &sys::GDExtensionGodotVersion) -> String {
-    let char_ptr = version_ptr.string;
-
-    // SAFETY: `version_ptr` points to a layout-compatible version struct.
-    let c_str = unsafe { std::ffi::CStr::from_ptr(char_ptr) };
-
-    String::from_utf8_lossy(c_str.to_bytes())
-        .as_ref()
-        .strip_prefix("Godot Engine ")
-        .unwrap_or(&String::from_utf8_lossy(c_str.to_bytes()))
-        .to_string()
-}

godot-ffi/src/lib.rs

@@ -63,7 +63,15 @@ mod toolbox;
 
 #[doc(hidden)]
 #[cfg(target_family = "wasm")]
-pub use gensym::gensym;
+pub use godot_macros::wasm_declare_init_fn;
+
+// No-op otherwise.
+#[doc(hidden)]
+#[cfg(not(target_family = "wasm"))]
+#[macro_export]
+macro_rules! wasm_declare_init_fn {
+    () => {};
+}
 
 pub use crate::godot_ffi::{GodotFfi, GodotNullableFfi, PrimitiveConversionError, PtrcallType};
 

godot-ffi/src/plugins.rs

@@ -25,25 +25,6 @@ macro_rules! plugin_registry {
     };
 }
 
-#[doc(hidden)]
-#[macro_export]
-// Following rustfmt::skip is no longer needed, but there are 2 workarounds good to know, thus preserved.
-// #[allow(clippy::deprecated_cfg_attr)]
-// #[cfg_attr(rustfmt, rustfmt::skip)]
-//   cfg_attr: workaround for https://github.com/rust-lang/rust/pull/52234#issuecomment-976702997
-macro_rules! plugin_execute_pre_main_wasm {
-    ($gensym:ident,) => {
-        // Rust presently requires that statics with a custom `#[link_section]` must be a simple
-        // list of bytes on the Wasm target (with no extra levels of indirection such as references).
-        //
-        // As such, instead we export a function with a random name of predictable format to be used by the embedder.
-        #[no_mangle]
-        extern "C" fn $gensym() {
-            __init();
-        }
-    };
-}
-
 /// Executes a block of code before main, by utilising platform specific linker instructions.
 #[doc(hidden)]
 #[macro_export]
@@ -73,8 +54,7 @@ macro_rules! plugin_execute_pre_main {
                 __inner_init
             };
 
-            #[cfg(target_family = "wasm")]
-            $crate::gensym! { $crate::plugin_execute_pre_main_wasm!() }
+            $crate::wasm_declare_init_fn!();
         };
     };
 }

godot-macros/Cargo.toml

@@ -12,8 +12,9 @@ homepage = "https://godot-rust.github.io"
 
 [features]
 api-custom = ["godot-bindings/api-custom"]
-register-docs = ["dep:markdown", "dep:litrs"]
 codegen-full = ["godot/__codegen-full"]
+experimental-wasm = ["dep:libc"]
+register-docs = ["dep:markdown", "dep:litrs"]
 
 [lib]
 proc-macro = true
@@ -25,9 +26,12 @@ quote = "1.0.29"
 # Enabled by `docs`.
 markdown = { version = "=1.0.0-alpha.21", optional = true }
 litrs = { version = "0.4.1", optional = true }
-# Requires bugfixes from 0.6.1.
 venial = "0.6.1"
 
+# Cannot use [target.'cfg(target_family = "wasm")'.dependencies], as proc-macro crates are always compiled for host platform, not target.
+# Thus solved via feature.
+libc = { version = "0.2.171", optional = true }
+
 [build-dependencies]
 godot-bindings = { path = "../godot-bindings", version = "=0.2.4" } # emit_godot_version_cfg
 

godot-macros/src/ffi_macros.rs

@@ -0,0 +1,42 @@
+/*
+ * Copyright (c) godot-rust; Bromeon and contributors.
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+//! Macro implementations used by `godot-ffi` crate.
+
+#![cfg(feature = "experimental-wasm")]
+
+use crate::util::bail;
+use crate::ParseResult;
+use proc_macro2::TokenStream;
+use quote::{format_ident, quote};
+
+pub(super) fn wasm_declare_init_fn(input: TokenStream) -> ParseResult<TokenStream> {
+    if !input.is_empty() {
+        return bail!(input, "macro expects no arguments");
+    }
+
+    // Create sufficiently unique identifier without entire `uuid` (let alone `rand`) crate dependency.
+    let a = unsafe { libc::rand() };
+    let b = unsafe { libc::rand() };
+
+    // Rust presently requires that statics with a custom `#[link_section]` must be a simple
+    // list of bytes on the Wasm target (with no extra levels of indirection such as references).
+    //
+    // As such, instead we export a function with a random name of known prefix to be used by the embedder.
+    // This prefix is queried at load time, see godot-macros/src/gdextension.rs.
+    let function_name = format_ident!("__godot_rust_registrant_{a}_{b}");
+
+    let code = quote! {
+        #[cfg(target_family = "wasm")] // Strictly speaking not necessary, as this macro is only invoked for Wasm.
+        #[no_mangle]
+        extern "C" fn #function_name() {
+            __init();
+        }
+    };
+
+    Ok(code)
+}

godot-macros/src/gdextension.rs

@@ -87,7 +87,7 @@ pub fn attribute_gdextension(item: venial::Item) -> ParseResult<TokenStream> {
                             console.log(`Patching Module with ${sym}`);
                             Module[sym] = dso_exports[sym];
                         }
-                    } else if (sym.startsWith("rust_gdext_registrant_")) {
+                    } else if (sym.startsWith("__godot_rust_registrant_")) {
                         registrants.push(sym);
                     }
                 }

godot-macros/src/lib.rs

@@ -15,6 +15,7 @@ mod class;
 mod derive;
 #[cfg(all(feature = "register-docs", since_api = "4.3"))]
 mod docs;
+mod ffi_macros;
 mod gdextension;
 mod itest;
 mod util;
@@ -774,9 +775,6 @@ pub fn derive_godot_class(input: TokenStream) -> TokenStream {
 /// method, you can access all declared signals in `self.signals().some_signal()` or `gd.signals().some_signal()`. The returned object is
 /// of type [`TypedSignal`], which provides further APIs for emitting and connecting, among others.
 ///
-/// Visibility of signals **must not exceed class visibility**. If your class is private (as above) and you declare your signal as `pub fn`,
-/// you will get a compile error "can't leak private type".
-///
 /// A detailed explanation with examples is available in the [book chapter _Registering signals_](https://godot-rust.github.io/book/register/signals.html).
 ///
 /// [`WithSignals`]: ../obj/trait.WithSignals.html
@@ -1051,9 +1049,21 @@ pub fn gdextension(meta: TokenStream, input: TokenStream) -> TokenStream {
 }
 
 // ----------------------------------------------------------------------------------------------------------------------------------------------
+// Used by godot-ffi
+
+/// Creates an initialization block for Wasm.
+#[proc_macro]
+#[cfg(feature = "experimental-wasm")]
+pub fn wasm_declare_init_fn(input: TokenStream) -> TokenStream {
+    translate_functional(input, ffi_macros::wasm_declare_init_fn)
+}
+
+// ----------------------------------------------------------------------------------------------------------------------------------------------
+// Implementation
 
 type ParseResult<T> = Result<T, venial::Error>;
 
+/// For `#[derive(...)]` derive macros.
 fn translate<F>(input: TokenStream, transform: F) -> TokenStream
 where
     F: FnOnce(venial::Item) -> ParseResult<TokenStream2>,
@@ -1067,6 +1077,7 @@ where
     TokenStream::from(result2)
 }
 
+/// For `#[proc_macro_attribute]` procedural macros.
 fn translate_meta<F>(
     self_name: &str,
     meta: TokenStream,
@@ -1087,6 +1098,18 @@ where
     TokenStream::from(result2)
 }
 
+/// For `#[proc_macro]` function-style macros.
+#[cfg(feature = "experimental-wasm")]
+fn translate_functional<F>(input: TokenStream, transform: F) -> TokenStream
+where
+    F: FnOnce(TokenStream2) -> ParseResult<TokenStream2>,
+{
+    let input2 = TokenStream2::from(input);
+    let result2 = transform(input2).unwrap_or_else(|e| e.to_compile_error());
+
+    TokenStream::from(result2)
+}
+
 /// Returns the index of the key in `keys` (if any) that is present.
 fn handle_mutually_exclusive_keys(
     parser: &mut KvParser,

godot/src/lib.rs

@@ -104,14 +104,18 @@
 //!   Support for WebAssembly exports is still a work-in-progress and is not yet well tested. This feature is in place for users
 //!   to explicitly opt in to any instabilities or rough edges that may result.
 //!
-//!   By default, Wasm threads are enabled and require the flag `"-C", "link-args=-sUSE_PTHREADS=1"` in the `wasm32-unknown-unknown` target.
+//!   Please read [Export to Web](https://godot-rust.github.io/book/toolchain/export-web.html) in the book.
+//!
+//!   By default, Wasm threads are enabled and require the flag `"-C", "link-args=-pthread"` in the `wasm32-unknown-unknown` target.
 //!   This must be kept in sync with Godot's Web export settings (threading support enabled). To disable it, use **additionally* the feature
 //!   `experimental-wasm-nothreads`.<br><br>
 //!
+//!   It is recommended to use this feature in combination with `lazy-function-tables` to reduce the size of the generated Wasm binary.
+//!
 //! * **`experimental-wasm-nothreads`**
 //!
 //!   Requires the `experimental-wasm` feature. Disables threading support for WebAssembly exports. This needs to be kept in sync with
-//!   Godot's Web export setting (threading support disabled), and must _not_ use the `"-C", "link-args=-sUSE_PTHREADS=1"` flag in the
+//!   Godot's Web export setting (threading support disabled), and must _not_ use the `"-C", "link-args=-pthread"` flag in the
 //!   `wasm32-unknown-unknown` target.<br><br>
 //!
 //! * **`codegen-rustfmt`**