feat: add catch_unwind protection to render to prevent Node.js process crashes

[yisibl]

Background

When the upstream resvg (Rust) encounters an SVG that cannot be rendered, it may panic. This causes the Node.js process to crash immediately, resulting in a core dump.

✅ Node.js

• Use catch_unwind in the resvg-js Rust layer to capture panics, converting them into explicit errors to prevent direct panics from crashing the Node.js process.
  https://doc.rust-lang.org/book/ch09-01-unrecoverable-errors-with-panic.html
• Remove unwrap() at critical points in the resvg-js rendering pipeline.

There are also some upstream PRs working towards this goal, but they haven't been merged yet:

• resvg_render() (C wrapper function) does not crash on incorrect input linebender/resvg#926
• DRAFT: Non-panicking C API linebender/resvg#472

🚧 Wasm

By default the wasm32-unknown-unknown target is compiled with -Cpanic=abort. Historically this was due to the fact that there was no way to catch panics in wasm, but since mid-2025 the WebAssembly exception-handling proposal reached stabilization. LLVM has support for this proposal as well and when this is all combined together it's possible to enable -Cpanic=unwind on wasm targets.
See https://doc.rust-lang.org/rustc/platform-support/wasm32-unknown-unknown.html#unwinding

However, considering that this would increase the size of the wasm file and require runtime support, we will not enable it at this time.

• 【Wasmtime】https://cfallin.org/blog/2025/11/06/exceptions/
• https://webassembly.org/features/
• https://github.com/WebAssembly/exception-handling
• https://rajrajhans.com/2023/07/handling-rust-panics-in-wasm/

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Project	Deployment	Review	Updated (UTC)
resvg-js	Ready	Preview, Comment	Jan 27, 2026 6:52am

[yisibl]

If future support for unwind is added to Wasm, it could be implemented this way:

// Share panic-to-error handling across Node.js and wasm targets.
macro_rules! render_inner_catch_unwind_impl {
    ($err_ty:ty) => {
        fn render_inner_catch_unwind(&self) -> Result<RenderedImage, $err_ty> {
            match std::panic::catch_unwind(AssertUnwindSafe(|| self.render_inner())) {
                Ok(result) => result.map_err(Into::into),
                Err(panic) => Err(Error::RenderPanic(panic_to_string(panic)).into()),
            }
        }
    };
}

#[cfg(not(target_arch = "wasm32"))]
impl Resvg {
    render_inner_catch_unwind_impl!(NapiError);
}

#[cfg(target_arch = "wasm32")]
impl Resvg {
    render_inner_catch_unwind_impl!(js_sys::Error);
}

For .cargo/config.toml

[target.wasm32-unknown-unknown]
rustflags = ["-Cpanic=unwind", "-Cllvm-args=-wasm-use-legacy-eh=false"]

[unstable]
build-std = ["std", "panic_unwind"]