3f9bff17c8
* Support disabling backtraces at compile time This commit adds support to Wasmtime to disable, at compile time, the gathering of backtraces on traps. The `wasmtime` crate now sports a `wasm-backtrace` feature which, when disabled, will mean that backtraces are never collected at compile time nor are unwinding tables inserted into compiled objects. The motivation for this commit stems from the fact that generating a backtrace is quite a slow operation. Currently backtrace generation is done with libunwind and `_Unwind_Backtrace` typically found in glibc or other system libraries. When thousands of modules are loaded into the same process though this means that the initial backtrace can take nearly half a second and all subsequent backtraces can take upwards of hundreds of milliseconds. Relative to all other operations in Wasmtime this is extremely expensive at this time. In the future we'd like to implement a more performant backtrace scheme but such an implementation would require coordination with Cranelift and is a big chunk of work that may take some time, so in the meantime if embedders don't need a backtrace they can still use this option to disable backtraces at compile time and avoid the performance pitfalls of collecting backtraces. In general I tried to originally make this a runtime configuration option but ended up opting for a compile-time option because `Trap::new` otherwise has no arguments and always captures a backtrace. By making this a compile-time option it was possible to configure, statically, the behavior of `Trap::new`. Additionally I also tried to minimize the amount of `#[cfg]` necessary by largely only having it at the producer and consumer sites. Also a noteworthy restriction of this implementation is that if backtrace support is disabled at compile time then reference types support will be unconditionally disabled at runtime. With backtrace support disabled there's no way to trace the stack of wasm frames which means that GC can't happen given our current implementation. * Always enable backtraces for the C API
wasmtime
A standalone runtime for WebAssembly
A Bytecode Alliance project
Guide | Contributing | Website | Chat
Installation
The Wasmtime CLI can be installed on Linux and macOS with a small install script:
$ curl https://wasmtime.dev/install.sh -sSf | bash
Windows or otherwise interested users can download installers and binaries directly from the GitHub Releases page.
Example
If you've got the Rust compiler installed then you can take some Rust source code:
fn main() {
println!("Hello, world!");
}
and compile/run it with:
$ rustup target add wasm32-wasi
$ rustc hello.rs --target wasm32-wasi
$ wasmtime hello.wasm
Hello, world!
Features
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Lightweight. Wasmtime is a standalone runtime for WebAssembly that scales with your needs. It fits on tiny chips as well as makes use of huge servers. Wasmtime can be embedded into almost any application too.
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Fast. Wasmtime is built on the optimizing Cranelift code generator to quickly generate high-quality machine code at runtime.
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Configurable. Whether you need to precompile your wasm ahead of time, or interpret it at runtime, Wasmtime has you covered for all your wasm-executing needs.
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WASI. Wasmtime supports a rich set of APIs for interacting with the host environment through the WASI standard.
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Standards Compliant. Wasmtime passes the official WebAssembly test suite, implements the official C API of wasm, and implements future proposals to WebAssembly as well. Wasmtime developers are intimately engaged with the WebAssembly standards process all along the way too.
Language Support
You can use Wasmtime from a variety of different languages through embeddings of the implementation:
- Rust - the
wasmtimecrate - C - the
wasm.h,wasi.h, andwasmtime.hheaders or usewasmtimeConan package - C++ - the
wasmtime-cpprepository or usewasmtime-cppConan package - Python - the
wasmtimePyPI package - .NET - the
WasmtimeNuGet package - Go - the
wasmtime-gorepository
Documentation
📚 Read the Wasmtime guide here! 📚
The wasmtime guide is the best starting point to learn about what Wasmtime can do for you or help answer your questions about Wasmtime. If you're curious in contributing to Wasmtime, it can also help you do that!
It's Wasmtime.