Preserve full native stack traces in errors (#823)

* Preserve full native stack traces in errors

This commit builds on #759 by performing a few refactorings:

* The `backtrace` crate is updated to 0.3.42 which incorporates the
  Windows-specific stack-walking code, so that's no longer needed.
* A full `backtrace::Backtrace` type is held in a trap at all times.
* The trap structures in the `wasmtime-*` internal crates were
  refactored a bit to preserve more information and deal with raw
  values rather than converting between various types and strings.
* The `wasmtime::Trap` type has been updated with these various changes.

Eventually I think we'll want to likely render full stack traces (and/or
partial wasm ones) into error messages, but for now that's left as-is
and we can always improve it later. I suspect the most relevant thing we
need to do is to implement function name symbolication for wasm
functions first, and then afterwards we can incorporate native function
names!

* Fix some test suite assertions

crates/api/Cargo.toml

@@ -18,6 +18,7 @@ anyhow = "1.0.19"
 region = "2.0.0"
 libc = "0.2"
 cfg-if = "0.1.9"
+backtrace = "0.3.42"
 
 [target.'cfg(target_os = "windows")'.dependencies]
 winapi = "0.3.7"

crates/api/src/callable.rs

@@ -156,12 +156,7 @@ impl WrappedCallable for WasmtimeFn {
                 )
             })
         } {
-            let message = error.0;
-            let backtrace = error.1;
-
-            let trap = take_api_trap().unwrap_or_else(|| {
-                Trap::new_with_trace(format!("call error: {}", message), backtrace)
-            });
+            let trap = take_api_trap().unwrap_or_else(|| Trap::from_jit(error));
             return Err(trap);
         }
 

crates/api/src/instance.rs

@@ -52,8 +52,8 @@ fn instantiate_in_context(
     let instance = compiled_module.instantiate().map_err(|e| -> Error {
         if let Some(trap) = take_api_trap() {
             trap.into()
-        } else if let InstantiationError::StartTrap(msg) = e {
-            Trap::new(msg).into()
+        } else if let InstantiationError::StartTrap(trap) = e {
+            Trap::from_jit(trap).into()
         } else {
             e.into()
         }

crates/api/src/trap.rs

@@ -1,7 +1,7 @@
 use crate::instance::Instance;
+use backtrace::Backtrace;
 use std::fmt;
 use std::sync::Arc;
-use wasmtime_runtime::{get_backtrace, Backtrace, BacktraceFrame};
 
 /// A struct representing an aborted instruction execution, with a message
 /// indicating the cause.
@@ -12,7 +12,8 @@ pub struct Trap {
 
 struct TrapInner {
     message: String,
-    trace: Vec<FrameInfo>,
+    wasm_trace: Vec<FrameInfo>,
+    native_trace: Backtrace,
 }
 
 fn _assert_trap_is_sync_and_send(t: &Trap) -> (&dyn Sync, &dyn Send) {
@@ -27,21 +28,29 @@ impl Trap {
     /// assert_eq!("unexpected error", trap.message());
     /// ```
     pub fn new<I: Into<String>>(message: I) -> Self {
-        Self::new_with_trace(message, get_backtrace())
+        Trap::new_with_trace(message.into(), Backtrace::new_unresolved())
     }
 
-    pub(crate) fn new_with_trace<I: Into<String>>(message: I, backtrace: Backtrace) -> Self {
-        let mut trace = Vec::with_capacity(backtrace.len());
-        for i in 0..backtrace.len() {
-            // Don't include frames without backtrace info.
-            if let Some(info) = FrameInfo::try_from(backtrace[i]) {
-                trace.push(info);
+    pub(crate) fn from_jit(jit: wasmtime_runtime::Trap) -> Self {
+        Trap::new_with_trace(jit.to_string(), jit.backtrace)
+    }
+
+    fn new_with_trace(message: String, native_trace: Backtrace) -> Self {
+        let mut wasm_trace = Vec::new();
+        for frame in native_trace.frames() {
+            let pc = frame.ip() as usize;
+            if let Some(info) = wasmtime_runtime::jit_function_registry::find(pc) {
+                wasm_trace.push(FrameInfo {
+                    func_index: info.func_index as u32,
+                    module_name: info.module_id.clone(),
+                })
             }
         }
         Trap {
             inner: Arc::new(TrapInner {
-                message: message.into(),
-                trace,
+                message,
+                wasm_trace,
+                native_trace,
             }),
         }
     }
@@ -52,7 +61,7 @@ impl Trap {
     }
 
     pub fn trace(&self) -> &[FrameInfo] {
-        &self.inner.trace
+        &self.inner.wasm_trace
     }
 }
 
@@ -60,7 +69,8 @@ impl fmt::Debug for Trap {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         f.debug_struct("Trap")
             .field("message", &self.inner.message)
-            .field("trace", &self.inner.trace)
+            .field("wasm_trace", &self.inner.wasm_trace)
+            .field("native_trace", &self.inner.native_trace)
             .finish()
     }
 }
@@ -99,17 +109,4 @@ impl FrameInfo {
     pub fn module_name(&self) -> Option<&str> {
         self.module_name.as_deref()
     }
-
-    pub(crate) fn try_from(backtrace: BacktraceFrame) -> Option<FrameInfo> {
-        if let Some(tag) = backtrace.tag() {
-            let func_index = tag.func_index as u32;
-            let module_name = tag.module_id.clone();
-            Some(FrameInfo {
-                func_index,
-                module_name,
-            })
-        } else {
-            None
-        }
-    }
 }