Pros of Wasmer

• Supports multiple backends (LLVM, Cranelift, Singlepass) for different performance/compilation speed trade-offs
• Provides a more extensive ecosystem with additional tools like Wasmer-JS and WAPM (WebAssembly Package Manager)
• Offers easier integration with various programming languages through language extensions

Cons of Wasmer

• Generally slower runtime performance compared to Wasmtime
• Less focus on standards compliance and cutting-edge WebAssembly features
• Smaller community and corporate backing compared to Wasmtime's Bytecode Alliance support

Code Comparison

Wasmer:

let module = Module::from_file(store, "example.wasm")?;
let import_object = imports! {};
let instance = Instance::new(&module, &import_object)?;
let sum = instance.exports.get_function("sum")?;
let result = sum.call(&[Value::I32(5), Value::I32(37)])?;

Wasmtime:

let engine = Engine::default();
let module = Module::from_file(&engine, "example.wasm")?;
let store = Store::new(&engine, ());
let instance = Instance::new(&store, &module, &[])?;
let sum = instance.get_func("sum").unwrap();
let result = sum.call(&[5.into(), 37.into()])?;

Both examples demonstrate loading a WebAssembly module, creating an instance, and calling a function. Wasmtime's API is slightly more explicit with separate Engine and Store concepts.

Pros of wabt

• Focused on WebAssembly binary toolkit utilities
• Provides a suite of command-line tools for working with WebAssembly
• Supports text-to-binary and binary-to-text conversions

Cons of wabt

• Limited runtime capabilities compared to Wasmtime
• Primarily a development and tooling project, not a full-featured runtime
• Less emphasis on performance optimization for WebAssembly execution

Code Comparison

wabt (wat2wasm example):

wat2wasm input.wat -o output.wasm

Wasmtime (running a WebAssembly module):

use wasmtime::*;

let engine = Engine::default();
let module = Module::from_file(&engine, "example.wasm")?;
let instance = Instance::new(&mut store, &module, &[])?;

Summary

wabt is a toolkit for WebAssembly binary manipulation and conversion, offering various command-line utilities. It's excellent for development and debugging but lacks runtime features. Wasmtime, on the other hand, is a full-featured WebAssembly runtime with a focus on performance and embedability. While wabt is more suited for tooling and development workflows, Wasmtime is better for executing and integrating WebAssembly modules in production environments.

Pros of Emscripten

• Mature ecosystem with extensive documentation and community support
• Broader compatibility with existing C/C++ codebases
• Includes a complete toolchain for compiling to WebAssembly

Cons of Emscripten

• Larger runtime overhead compared to Wasmtime
• Less focus on performance optimization for server-side WebAssembly
• More complex setup and configuration process

Code Comparison

Emscripten (compiling C++ to WebAssembly):

#include <emscripten.h>
#include <iostream>

EMSCRIPTEN_KEEPALIVE
extern "C" int add(int a, int b) {
    return a + b;
}

Wasmtime (running WebAssembly module in Rust):

use wasmtime::*;

let engine = Engine::default();
let module = Module::from_file(&engine, "add.wasm")?;
let instance = Instance::new(&mut store, &module, &[])?;
let add = instance.get_func(&mut store, "add")?;
let result = add.call(&mut store, &[Val::I32(5), Val::I32(37)])?;

This comparison highlights the different approaches of Emscripten and Wasmtime. Emscripten focuses on compiling existing code to WebAssembly, while Wasmtime provides a runtime for executing WebAssembly modules. The choice between them depends on specific project requirements and use cases.

Pros of WAVM

• Supports a wider range of WebAssembly features, including SIMD and threading
• Provides more low-level control over the execution environment
• Offers better performance for certain use cases, especially compute-intensive tasks

Cons of WAVM

• Less actively maintained compared to Wasmtime
• Smaller community and ecosystem support
• More complex to set up and use, with fewer high-level abstractions

Code Comparison

WAVM example:

#include "WAVM/Runtime/Runtime.h"
#include "WAVM/Runtime/Linker.h"

WAVM::Runtime::ModuleRef module = WAVM::Runtime::loadModule(wasmBytes);
WAVM::Runtime::Instance* instance = WAVM::Runtime::instantiateModule(compartment, module, {}, "module");

Wasmtime example:

use wasmtime::*;

let engine = Engine::default();
let module = Module::from_binary(&engine, wasm_bytes)?;
let instance = Instance::new(&mut store, &module, &[])?;

Both WAVM and Wasmtime are WebAssembly runtimes, but they have different focuses and trade-offs. WAVM offers more advanced features and potentially better performance for specific scenarios, while Wasmtime provides a more user-friendly experience with better community support and active development. The choice between them depends on the specific requirements of your project and the level of control you need over the WebAssembly execution environment.