Test backtrace attached to Trap

Author: kateinoigakukun

Sources/WasmKit/Execution/NameRegistry.swift

@@ -19,6 +19,13 @@ struct NameRegistry {
                     registry.register(instance: instance, nameMap: nameMap)
                 }
             }
+
+            for (name, entry) in instance.exports {
+                // Use exported name if the function doesn't have name in name section.
+                guard case .function(let function) = entry else { continue }
+                guard registry.functionNames[function] == nil else { continue }
+                registry.functionNames[function] = name
+            }
         }
     }
 
@@ -48,7 +55,7 @@ struct NameRegistry {
         }
         // Fallback
         if function.isWasm {
-            return "function[\(function.wasm.index)]"
+            return "wasm function[\(function.wasm.index)]"
         } else {
             return "unknown host function"
         }

Tests/WATTests/EncoderTests.swift

@@ -147,7 +147,7 @@ class EncoderTests: XCTestCase {
             """,
             options: EncodeOptions(nameSection: true)
         )
-        
+
         var parser = WasmParser.Parser(bytes: bytes)
         var customSections: [CustomSection] = []
         while let payload = try parser.parseNext() {

Tests/WasmKitTests/ExecutionTests.swift

@@ -51,4 +51,49 @@ final class ExecutionTests: XCTestCase {
         let results = try _start()
         XCTAssertEqual(results, [.i32(42)])
     }
+
+    func testBacktrace() throws {
+        let module = try parseWasm(
+            bytes: wat2wasm(
+                """
+                (module
+                  (memory (export "memory") 1)
+                  (func $foo (result i32)
+                    unreachable
+                  )
+                  (func $bar (result i32)
+                    (call $foo)
+                  )
+                  (func (export "_start")
+                    (call $bar)
+                    (drop)
+                  )
+                )
+                """,
+                options: EncodeOptions(nameSection: true)
+            )
+        )
+
+        let engine = Engine()
+        let store = Store(engine: engine)
+        let instance = try module.instantiate(store: store)
+        let _start = try XCTUnwrap(instance.exports[function: "_start"])
+
+        let trap: Trap
+        do {
+            try _start()
+            XCTFail("expect unreachable trap")
+            return
+        } catch let error {
+            trap = try XCTUnwrap(error as? Trap)
+        }
+
+        XCTAssertEqual(
+            trap.backtrace?.symbols.compactMap(\.?.name),
+            [
+                "foo",
+                "bar",
+                "_start",
+            ])
+    }
 }