[Stack Switching] Reset the continuation state in --fuzz-exec on unhandled suspends (#7823)

Like wasm-shell, we must reset the global state in such a
case.

Author: kripken

scripts/test/fuzzing.py

@@ -114,6 +114,7 @@
     'vacuum-stack-switching.wast',
     'cont.wast',
     'cont_simple.wast',
+    'cont_many_unhandled.wast',
     # TODO: fix split_wast() on tricky escaping situations like a string ending
     #       in \\" (the " is not escaped - there is an escaped \ before it)
     'string-lifting-section.wast',

src/tools/execution-results.h

@@ -476,6 +476,7 @@ struct ExecutionResults {
       auto flow = instance.callFunction(func->name, arguments);
       if (flow.suspendTag) { // TODO: support stack switching here
         std::cout << "[exception thrown: unhandled suspend]" << std::endl;
+        instance.clearContinuationStore();
         return Exception{};
       }
       return flow.values;

test/lit/exec/cont_many_unhandled.wast

@@ -0,0 +1,40 @@
+;; NOTE: Assertions have been generated by update_lit_checks.py --output=fuzz-exec and should not be edited.
+
+;; RUN: foreach %s %t wasm-opt -all --fuzz-exec-before -q -o /dev/null 2>&1 | filecheck %s
+
+;; Three exports, one which throws from a resume, and two that do unhandled
+;; suspends. This is a regression test for a bug where the global state of
+;; continuations got into a confused state at the last export, and asserted.
+
+(module
+  (type $none (func))
+  (type $cont (cont $none))
+
+  (tag $tag (type $none))
+
+  (func $empty
+  )
+
+  ;; CHECK:      [fuzz-exec] calling a
+  ;; CHECK-NEXT: [exception thrown: tag ()]
+  (func $a (export "a")
+    (resume_throw $cont $tag
+      (cont.new $cont
+        (ref.func $empty)
+      )
+    )
+  )
+
+  ;; CHECK:      [fuzz-exec] calling b
+  ;; CHECK-NEXT: [exception thrown: unhandled suspend]
+  (func $b (export "b")
+    (suspend $tag)
+  )
+
+  ;; CHECK:      [fuzz-exec] calling c
+  ;; CHECK-NEXT: [exception thrown: unhandled suspend]
+  (func $c (export "c")
+    (suspend $tag)
+  )
+)
+