Add proxy_wasm::main macro. (#141)

This is primarly a mechanism to deliver a workaround for a breaking
change in Rust v1.56.0 (which updated LLVM to v13.0), which changed
existing reactors into multi-entry commands, leading to performance
degradation and/or unusable Proxy-Wasm plugins.

See: WebAssembly/WASI#471

This is delivered as a macro to make it somehow compatible with the
unstable "-Z wasi-exec-model=reactor" feature.

Signed-off-by: Piotr Sikora <piotrsikora@google.com>

Author: PiotrSikora

.github/workflows/rust.yml

@@ -195,6 +195,43 @@ jobs:
     - name: Package (publish)
       run: cargo publish --dry-run --target=wasm32-unknown-unknown
 
+  reactor:
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v2
+
+    - name: Update Rust
+      run: |
+        rustup toolchain install nightly --component clippy
+        rustup +nightly target add wasm32-wasi
+        rustup default nightly
+
+    - name: Rewrite Cargo.toml examples
+      run: |
+        grep -v '^crate-type' Cargo.toml > Cargo.tmp
+        mv Cargo.tmp Cargo.toml
+
+    - name: Build (wasm32-wasi)
+      env:
+        RUSTFLAGS: -D warnings -C link-args=-S -Z wasi-exec-model=reactor
+      run: cargo build --release --all-targets --target=wasm32-wasi
+
+    - name: Build (wasm32-wasi with wee-alloc)
+      env:
+        RUSTFLAGS: -D warnings -C link-args=-S -Z wasi-exec-model=reactor
+      run: cargo build --release --all-targets --target=wasm32-wasi --features=wee-alloc
+
+    - name: Clippy (wasm32-wasi)
+      env:
+        RUSTFLAGS: -D warnings -C link-args=-S -Z wasi-exec-model=reactor
+      run: cargo clippy --release --all-targets --target=wasm32-wasi
+
+    - name: Clippy (wasm32-wasi with wee-alloc)
+      env:
+        RUSTFLAGS: -D warnings -C link-args=-S -Z wasi-exec-model=reactor
+      run: cargo clippy --release --all-targets --target=wasm32-wasi --features=wee-alloc
+
   outdated:
     runs-on: ubuntu-latest
 

BUILD

@@ -1,11 +1,21 @@
+load("@rules_rust//cargo:cargo_build_script.bzl", "cargo_build_script")
 load("@rules_rust//rust:defs.bzl", "rust_library")
 
+cargo_build_script(
+    name = "proxy_wasm_build_script",
+    srcs = ["build.rs"],
+    edition = "2018",
+    tags = ["manual"],
+    visibility = ["//visibility:private"],
+)
+
 rust_library(
     name = "proxy_wasm",
     srcs = glob(["src/*.rs"]),
     edition = "2018",
     visibility = ["//visibility:public"],
     deps = [
+        ":proxy_wasm_build_script",
         "//bazel/cargo:hashbrown",
         "//bazel/cargo:log",
     ],

CHANGELOG.md

@@ -6,6 +6,12 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
 ## [Unreleased]
 
+### Fixed
+
+- Fixed performance degradation with `wasm32-wasi` target in Rust v1.56.0
+  or newer by adding `proxy_wasm::main` macro that should be used instead
+  of custom `_start`, `_initialize` and/or `main` exports.
+
 ### Changed
 
 - Updated ABI to Proxy-Wasm ABI v0.2.1.

Cargo.toml

@@ -7,6 +7,7 @@ readme = "README.md"
 license = "Apache-2.0"
 repository = "https://github.com/proxy-wasm/proxy-wasm-rust-sdk"
 edition = "2018"
+build = "build.rs"
 
 [features]
 wee-alloc = ["wee_alloc"]

build.rs

@@ -0,0 +1,33 @@
+// Copyright 2022 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+fn main() {
+    println!("cargo:rerun-if-changed=build.rs");
+    println!("cargo:rerun-if-env-changed=RUSTFLAGS");
+
+    if let Some(target_os) = std::env::var_os("CARGO_CFG_TARGET_OS") {
+        if target_os != "wasi" {
+            return;
+        }
+    }
+
+    if let Some(rustflags) = std::env::var_os("CARGO_ENCODED_RUSTFLAGS") {
+        for flag in rustflags.to_string_lossy().split('\x1f') {
+            if flag.ends_with("wasi-exec-model=reactor") {
+                println!("cargo:rustc-cfg=wasi_exec_model_reactor");
+                return;
+            }
+        }
+    }
+}

examples/hello_world.rs

@@ -22,11 +22,10 @@ use std::time::Duration;
 #[cfg(not(all(target_arch = "wasm32", target_os = "unknown")))]
 use getrandom::getrandom;
 
-#[no_mangle]
-pub fn _start() {
+proxy_wasm::main! {{
     proxy_wasm::set_log_level(LogLevel::Trace);
     proxy_wasm::set_root_context(|_| -> Box<dyn RootContext> { Box::new(HelloWorld) });
-}
+}}
 
 struct HelloWorld;
 

examples/http_auth_random.rs

@@ -17,11 +17,10 @@ use proxy_wasm::traits::*;
 use proxy_wasm::types::*;
 use std::time::Duration;
 
-#[no_mangle]
-pub fn _start() {
+proxy_wasm::main! {{
     proxy_wasm::set_log_level(LogLevel::Trace);
     proxy_wasm::set_http_context(|_, _| -> Box<dyn HttpContext> { Box::new(HttpAuthRandom) });
-}
+}}
 
 struct HttpAuthRandom;
 

examples/http_body.rs

@@ -15,11 +15,10 @@
 use proxy_wasm::traits::*;
 use proxy_wasm::types::*;
 
-#[no_mangle]
-pub fn _start() {
+proxy_wasm::main! {{
     proxy_wasm::set_log_level(LogLevel::Trace);
     proxy_wasm::set_root_context(|_| -> Box<dyn RootContext> { Box::new(HttpBodyRoot) });
-}
+}}
 
 struct HttpBodyRoot;
 

examples/http_config.rs

@@ -15,15 +15,14 @@
 use proxy_wasm::traits::*;
 use proxy_wasm::types::*;
 
-#[no_mangle]
-pub fn _start() {
+proxy_wasm::main! {{
     proxy_wasm::set_log_level(LogLevel::Trace);
     proxy_wasm::set_root_context(|_| -> Box<dyn RootContext> {
         Box::new(HttpConfigHeaderRoot {
             header_content: String::new(),
         })
     });
-}
+}}
 
 struct HttpConfigHeader {
     header_content: String,

examples/http_headers.rs

@@ -16,11 +16,10 @@ use log::trace;
 use proxy_wasm::traits::*;
 use proxy_wasm::types::*;
 
-#[no_mangle]
-pub fn _start() {
+proxy_wasm::main! {{
     proxy_wasm::set_log_level(LogLevel::Trace);
     proxy_wasm::set_root_context(|_| -> Box<dyn RootContext> { Box::new(HttpHeadersRoot) });
-}
+}}
 
 struct HttpHeadersRoot;
 

src/lib.rs

@@ -20,6 +20,40 @@ mod allocator;
 mod dispatcher;
 mod logger;
 
+// For crate-type="cdylib".
+#[cfg(not(wasi_exec_model_reactor))]
+#[macro_export]
+macro_rules! main {
+    ($code:block) => {
+        #[cfg(target_os = "wasi")]
+        extern "C" {
+            fn __wasm_call_ctors();
+        }
+
+        #[no_mangle]
+        pub extern "C" fn _initialize() {
+            #[cfg(target_os = "wasi")]
+            unsafe {
+                __wasm_call_ctors();
+            }
+
+            $code;
+        }
+    };
+}
+
+// For crate-type="bin" with RUSTFLAGS="-Z wasi-exec-model=reactor".
+#[cfg(wasi_exec_model_reactor)]
+#[macro_export]
+macro_rules! main {
+    ($code:block) => {
+        pub fn main() -> Result<(), Box<dyn std::error::Error>> {
+            $code;
+            Ok(())
+        }
+    };
+}
+
 pub fn set_log_level(level: types::LogLevel) {
     logger::set_log_level(level);
 }