C++ API: Make wasmtime::Store::gc return a Result (#12439)

* C++ API: Make `Store::gc()` return a `Result`

* Handle GC errors in C++ example programs

* clang format

Author: fitzgen

crates/c-api/include/wasmtime/store.hh

@@ -233,7 +233,7 @@ public:
 
   /// Runs a garbage collection pass in the referenced store to collect loose
   /// GC-managed objects, if any are available.
-  void gc() { context().gc(); }
+  Result<std::monostate> gc() { return context().gc(); }
 
 private:
   template <typename F>

examples/anyref.cc

@@ -95,7 +95,10 @@ int main() {
   }
 
   std::cout << "GCing within the store...\n";
-  store.context().gc();
+  if (!store.context().gc()) {
+    std::cerr << "> Error while collecting garbage\n";
+    return 1;
+  }
 
   std::cout << "Done.\n";
   return 0;

examples/externref.cc

@@ -50,5 +50,10 @@ int main() {
             << "\n";
 
   std::cout << "Running a gc..\n";
-  store.context().gc();
+  if (!store.context().gc()) {
+    std::cerr << "> Error while collecting garbage\n";
+    return 1;
+  }
+
+  return 0;
 }