pub struct WasmBacktrace { /* private fields */ }
runtime
only.Expand description
Representation of a backtrace of function frames in a WebAssembly module for where an error happened.
This structure is attached to the anyhow::Error
returned from many
Wasmtime functions that execute WebAssembly such as Instance::new
or
Func::call
. This can be acquired with the anyhow::Error::downcast
family of methods to programmatically inspect the backtrace. Otherwise since
it’s part of the error returned this will get printed along with the rest of
the error when the error is logged.
Capturing of wasm backtraces can be configured through the
Config::wasm_backtrace
method.
For more information about errors in wasmtime see the documentation of the
Trap
type.
§Examples
let engine = Engine::default();
let module = Module::new(
&engine,
r#"
(module
(func $start (export "run")
call $trap)
(func $trap
unreachable)
)
"#,
)?;
let mut store = Store::new(&engine, ());
let instance = Instance::new(&mut store, &module, &[])?;
let func = instance.get_typed_func::<(), ()>(&mut store, "run")?;
let error = func.call(&mut store, ()).unwrap_err();
let bt = error.downcast_ref::<WasmBacktrace>().unwrap();
let frames = bt.frames();
assert_eq!(frames.len(), 2);
assert_eq!(frames[0].func_name(), Some("trap"));
assert_eq!(frames[1].func_name(), Some("start"));
Implementations§
source§impl WasmBacktrace
impl WasmBacktrace
sourcepub fn capture(store: impl AsContext) -> WasmBacktrace
pub fn capture(store: impl AsContext) -> WasmBacktrace
Captures a trace of the WebAssembly frames on the stack for the provided store.
This will return a WasmBacktrace
which holds captured
FrameInfo
s for each frame of WebAssembly on the call stack of the
current thread. If no WebAssembly is on the stack then the returned
backtrace will have no frames in it.
Note that this function will respect the Config::wasm_backtrace
configuration option and will return an empty backtrace if that is
disabled. To always capture a backtrace use the
WasmBacktrace::force_capture
method.
Also note that this function will only capture frames from the
specified store
on the stack, ignoring frames from other stores if
present.
§Example
let engine = Engine::default();
let module = Module::new(
&engine,
r#"
(module
(import "" "" (func $host))
(func $foo (export "f") call $bar)
(func $bar call $host)
)
"#,
)?;
let mut store = Store::new(&engine, ());
let func = Func::wrap(&mut store, |cx: Caller<'_, ()>| {
let trace = WasmBacktrace::capture(&cx);
println!("{trace:?}");
});
let instance = Instance::new(&mut store, &module, &[func.into()])?;
let func = instance.get_typed_func::<(), ()>(&mut store, "f")?;
func.call(&mut store, ())?;
sourcepub fn force_capture(store: impl AsContext) -> WasmBacktrace
pub fn force_capture(store: impl AsContext) -> WasmBacktrace
Unconditionally captures a trace of the WebAssembly frames on the stack for the provided store.
Same as WasmBacktrace::capture
except that it disregards the
Config::wasm_backtrace
setting and
always captures a backtrace.
Trait Implementations§
source§impl Debug for WasmBacktrace
impl Debug for WasmBacktrace
Auto Trait Implementations§
impl Freeze for WasmBacktrace
impl !RefUnwindSafe for WasmBacktrace
impl Send for WasmBacktrace
impl Sync for WasmBacktrace
impl Unpin for WasmBacktrace
impl !UnwindSafe for WasmBacktrace
Blanket Implementations§
source§impl<T> BorrowMut<T> for Twhere
T: ?Sized,
impl<T> BorrowMut<T> for Twhere
T: ?Sized,
source§fn borrow_mut(&mut self) -> &mut T
fn borrow_mut(&mut self) -> &mut T
source§impl<T> IntoEither for T
impl<T> IntoEither for T
source§fn into_either(self, into_left: bool) -> Either<Self, Self>
fn into_either(self, into_left: bool) -> Either<Self, Self>
self
into a Left
variant of Either<Self, Self>
if into_left
is true
.
Converts self
into a Right
variant of Either<Self, Self>
otherwise. Read moresource§fn into_either_with<F>(self, into_left: F) -> Either<Self, Self>
fn into_either_with<F>(self, into_left: F) -> Either<Self, Self>
self
into a Left
variant of Either<Self, Self>
if into_left(&self)
returns true
.
Converts self
into a Right
variant of Either<Self, Self>
otherwise. Read more