wasm-interp: Fix off-by-one in DoThrow (#2486)

Author: SoniEx2

src/interp/interp.cc

@@ -2615,7 +2615,8 @@ RunResult Thread::DoThrow(Exception::Ptr exn) {
     auto iter = handlers.rbegin();
     while (iter != handlers.rend()) {
       const HandlerDesc& handler = *iter;
-      if (pc >= handler.try_start_offset && pc < handler.try_end_offset) {
+      // pc points to the *next* instruction by the time we're in DoThrow.
+      if (pc > handler.try_start_offset && pc <= handler.try_end_offset) {
         // For a try-delegate, skip part of the traversal by directly going
         // up to an outer handler specified by the delegate depth.
         if (handler.kind == HandlerKind::Delegate) {

test/regress/interp-throw-before-try.txt

@@ -0,0 +1,19 @@
+;;; TOOL: run-interp-spec
+;;; ARGS*: --enable-exceptions
+(module
+  (tag $e0)
+  (func (export "throws")
+    (throw $e0)
+    (try $try
+      (do
+      )
+      (catch $e0)
+    )
+  )
+)
+
+(assert_exception (invoke "throws"))
+(;; STDOUT ;;;
+out/test/regress/interp-throw-before-try.txt:15: assert_exception passed
+2/2 tests passed.
+;;; STDOUT ;;)