Improve exception handling

ext/witapi/bindgen/rb-abi-guest.c

@@ -201,3 +201,7 @@ void __wasm_export_rb_abi_guest_rstring_ptr_post_return(int32_t arg0) {
     free((void*) (*((int32_t*) (arg0 + 0))));
   }
 }
+__attribute__((export_name("rb-vm-bugreport: func() -> ()")))
+void __wasm_export_rb_abi_guest_rb_vm_bugreport(void) {
+  rb_abi_guest_rb_vm_bugreport();
+}

ext/witapi/bindgen/rb-abi-guest.h

@@ -67,6 +67,7 @@ extern "C"
   rb_abi_guest_rb_abi_value_t rb_abi_guest_rb_errinfo(void);
   void rb_abi_guest_rb_clear_errinfo(void);
   void rb_abi_guest_rstring_ptr(rb_abi_guest_rb_abi_value_t value, rb_abi_guest_string_t *ret0);
+  void rb_abi_guest_rb_vm_bugreport(void);
   #ifdef __cplusplus
 }
 #endif

ext/witapi/bindgen/rb-abi-guest.wit

@@ -16,3 +16,5 @@ rb-errinfo: func() -> rb-abi-value
 rb-clear-errinfo: func()
 
 rstring-ptr: func(value: rb-abi-value) -> string
+
+rb-vm-bugreport: func()

ext/witapi/witapi-core.c

@@ -247,4 +247,8 @@ uint32_t rb_abi_guest_rb_abi_value_data_ptr(rb_abi_guest_rb_abi_value_t self) {
   return (uint32_t)DATA_PTR(obj);
 }
 
+void rb_vm_bugreport(const void *);
+
+void rb_abi_guest_rb_vm_bugreport(void) { rb_vm_bugreport(NULL); }
+
 void Init_witapi(void) {}

packages/npm-packages/ruby-wasm-wasi/src/bindgen/rb-abi-guest.d.ts

@@ -79,6 +79,7 @@ export class RbAbiGuest {
   rbErrinfo(): RbAbiValue;
   rbClearErrinfo(): void;
   rstringPtr(value: RbAbiValue): string;
+  rbVmBugreport(): void;
 }
 
 export class RbIseq {

packages/npm-packages/ruby-wasm-wasi/src/bindgen/rb-abi-guest.js

@@ -158,6 +158,9 @@ export class RbAbiGuest {
     this._exports["cabi_post_rstring-ptr"](ret);
     return result1;
   }
+  rbVmBugreport() {
+    this._exports['rb-vm-bugreport: func() -> ()']();
+  }
 }
 
 export class RbIseq {

packages/npm-packages/ruby-wasm-wasi/src/index.ts

@@ -406,6 +406,12 @@ class RbExceptionFormatter {
     })();
 
     const backtrace = error.call("backtrace");
+    if (backtrace.call("nil?").toString() === "true") {
+      return this.formatString(
+        error.call("class").toString(),
+        error.toString()
+      );
+    }
     const firstLine = backtrace.call("at", zeroLiteral);
     const restLines = backtrace
       .call("drop", oneLiteral)
@@ -419,9 +425,13 @@ class RbExceptionFormatter {
   formatString(
     klass: string,
     message: string,
-    backtrace: [string, string]
+    backtrace?: [string, string]
   ): string {
-    return `${backtrace[0]}: ${message} (${klass})\n${backtrace[1]}`;
+    if (backtrace) {
+      return `${backtrace[0]}: ${message} (${klass})\n${backtrace[1]}`;
+    } else {
+      return `${klass}: ${message}`;
+    }
   }
 }
 
@@ -461,6 +471,21 @@ const checkStatusTag = (
   }
 };
 
+function wrapRbOperation<R>(vm: RubyVM, body: () => R): R {
+  try {
+    return body();
+  } catch (e) {
+    if (e instanceof WebAssembly.RuntimeError && e.message === "unreachable") {
+      vm.guest.rbVmBugreport();
+      const error = new RbError(`Something went wrong in Ruby VM: ${e}`);
+      error.stack = e.stack;
+      throw error;
+    } else {
+      throw e;
+    }
+  }
+}
+
 const callRbMethod = (
   vm: RubyVM,
   privateObject: RubyVMPrivate,
@@ -469,14 +494,18 @@ const callRbMethod = (
   args: RbAbi.RbAbiValue[]
 ) => {
   const mid = vm.guest.rbIntern(callee + "\0");
-  const [value, status] = vm.guest.rbFuncallvProtect(recv, mid, args);
-  checkStatusTag(status, vm, privateObject);
-  return value;
+  return wrapRbOperation(vm, () => {
+    const [value, status] = vm.guest.rbFuncallvProtect(recv, mid, args);
+    checkStatusTag(status, vm, privateObject);
+    return value;
+  });
 };
 const evalRbCode = (vm: RubyVM, privateObject: RubyVMPrivate, code: string) => {
-  const [value, status] = vm.guest.rbEvalStringProtect(code + "\0");
-  checkStatusTag(status, vm, privateObject);
-  return new RbValue(value, vm, privateObject);
+  return wrapRbOperation(vm, () => {
+    const [value, status] = vm.guest.rbEvalStringProtect(code + "\0");
+    checkStatusTag(status, vm, privateObject);
+    return new RbValue(value, vm, privateObject);
+  });
 };
 
 /**