[Exceptions] Fix error on bad delegate index (#5587)

Fixes #5584

3 files changed, 23 insertions, 1 deletions

diff --git a/src/wasm/wasm-binary.cpp b/src/wasm/wasm-binary.cpp
index 9368325b0..5326972b0 100644
--- a/src/wasm/wasm-binary.cpp
+++ b/src/wasm/wasm-binary.cpp
@@ -2560,7 +2560,12 @@ void WasmBinaryBuilder::readFunctions() {
       assert(depth == 0);
       assert(breakStack.empty());
       assert(breakTargetNames.empty());
-      assert(exceptionTargetNames.empty());
+      if (!exceptionTargetNames.empty()) {
+        // A delegate index existed that did not end up referring to any valid
+        // outer try-catch (we remove valid ones from exceptionTargetNames as we
+        // go).
+        throwError("exceptionTargetNames not empty - invalid delegate");
+      }
       if (!expressionStack.empty()) {
         throwError("stack not empty on function exit");
       }
diff --git a/test/lit/binary/bad-delegate.test b/test/lit/binary/bad-delegate.test
new file mode 100644
index 000000000..8e6a011a5
--- /dev/null
+++ b/test/lit/binary/bad-delegate.test
@@ -0,0 +1,17 @@
+;; Test that we error properly on a file with a bad delegate (a delegate of an
+;; index that does not refer to a valid try-catch).
+
+;; Disassembled binary from wabt:
+;;
+;; (module
+;;   (type (;0;) (func))
+;;   (func (;0;) (type 0)
+;;     block  ;; label = @1
+;;       try  ;; label = @2
+;;         nop
+;;       delegate 0
+;;     end))
+
+;; RUN: not wasm-opt -all %s.wasm 2>&1 | filecheck %s
+
+;; CHECK: exceptionTargetNames not empty - invalid delegate
diff --git a/test/lit/binary/bad-delegate.test.wasm b/test/lit/binary/bad-delegate.test.wasm
new file mode 100644
index 000000000..db9645e35
--- /dev/null
+++ b/test/lit/binary/bad-delegate.test.wasm