fix: resolve crashes on invalid script hot reload

src/ScriptEngine.cpp

@@ -6,7 +6,7 @@
 #include <sstream>
 #include <assert.h>
 
-ScriptEngine::ScriptEngine() : engine(nullptr), updateFunc(nullptr), drawFunc(nullptr) {
+ScriptEngine::ScriptEngine() : engine(nullptr), updateFunc(nullptr), drawFunc(nullptr), currentModule(nullptr), hasValidScript(false) {
 }
 
 ScriptEngine::~ScriptEngine() {
@@ -37,54 +37,105 @@ bool ScriptEngine::Initialize() {
 }
 
 void ScriptEngine::Shutdown() {
+    ClearCachedFunctions();
     if (engine) {
         engine->ShutDownAndRelease();
         engine = nullptr;
     }
-    updateFunc = nullptr;
-    drawFunc = nullptr;
+    currentModule = nullptr;
+    hasValidScript = false;
 }
 
 bool ScriptEngine::CompileScript(const std::string& filename) {
     if (!engine) return false;
 
-    engine->GarbageCollect();
-    asIScriptModule* mod = engine->GetModule("main", asGM_ALWAYS_CREATE);
-
     std::string code = ReadFile(filename);
     if (code.empty()) {
         std::cerr << "Failed to read script file: " << filename << "\n";
         return false;
     }
 
-    int r = mod->AddScriptSection(filename.c_str(), code.c_str());
-    if (r < 0) return false;
+    // Try to compile in a temporary module first
+    asIScriptModule* tempMod = engine->GetModule("temp", asGM_ALWAYS_CREATE);
+    
+    int r = tempMod->AddScriptSection(filename.c_str(), code.c_str());
+    if (r < 0) {
+        std::cerr << "Failed to add script section for: " << filename << "\n";
+        engine->DiscardModule("temp");
+        return false;
+    }
 
-    r = mod->Build();
-    if (r < 0) return false;
+    r = tempMod->Build();
+    if (r < 0) {
+        std::cerr << "Failed to build script: " << filename << "\n";
+        engine->DiscardModule("temp");
+        return false;
+    }
 
-    // Cache Update(float dt) and Draw() functions if they exist
-    updateFunc = mod->GetFunctionByName("Update");
-    drawFunc = mod->GetFunctionByName("Draw");
+    // If we get here, compilation succeeded
+    // Now safely replace the main module
+    if (currentModule) {
+        engine->DiscardModule("main");
+    }
+    
+    // Create new main module with the working code
+    currentModule = engine->GetModule("main", asGM_ALWAYS_CREATE);
+    r = currentModule->AddScriptSection(filename.c_str(), code.c_str());
+    if (r >= 0) {
+        r = currentModule->Build();
+    }
+    
+    // Clean up temp module
+    engine->DiscardModule("temp");
+    
+    if (r < 0) {
+        // This shouldn't happen since we already tested compilation
+        std::cerr << "Unexpected error when creating main module\n";
+        ClearCachedFunctions();
+        return false;
+    }
+
+    // Cache new functions
+    updateFunc = currentModule->GetFunctionByName("Update");
+    drawFunc = currentModule->GetFunctionByName("Draw");
+    hasValidScript = true;
 
     std::cout << "Script compiled and cached: " << filename << "\n";
     return true;
 }
 
 void ScriptEngine::CallScriptFunction(asIScriptFunction* func, float dt) {
-    if (!func || !engine) return;
+    if (!func || !engine || !hasValidScript) return;
 
     asIScriptContext* ctx = engine->CreateContext();
-    ctx->Prepare(func);
+    if (!ctx) return;
+
+    int r = ctx->Prepare(func);
+    if (r < 0) {
+        ctx->Release();
+        return;
+    }
 
     if (func->GetParamCount() == 1) {
         ctx->SetArgFloat(0, dt);
     }
 
-    ctx->Execute();
+    r = ctx->Execute();
+    if (r != asEXECUTION_FINISHED) {
+        if (r == asEXECUTION_EXCEPTION) {
+            std::cerr << "Script exception: " << ctx->GetExceptionString() << "\n";
+        }
+    }
+
     ctx->Release();
 }
 
+void ScriptEngine::ClearCachedFunctions() {
+    updateFunc = nullptr;
+    drawFunc = nullptr;
+    hasValidScript = false;
+}
+
 void ScriptEngine::GarbageCollect() {
     if (engine) {
         engine->GarbageCollect();