Fixed issue #1, the second instance crashes with a fatal error (UE 5+)

Author: mrbindraw

CheckAppInstance.uplugin

@@ -19,7 +19,7 @@
 		{
 			"Name": "CheckAppInstance",
 			"Type": "Runtime",
-			"LoadingPhase": "Default",
+			"LoadingPhase": "EarliestPossible",
 			"WhitelistPlatforms": [
                 "Win64"
             ]

Source/CheckAppInstance/Private/CheckAppInstanceBPLibrary.cpp

@@ -11,15 +11,18 @@ UCheckAppInstanceBPLibrary::UCheckAppInstanceBPLibrary(const FObjectInitializer&
 
 void UCheckAppInstanceBPLibrary::CheckAnotherAppInstance(bool bIsEnabled)
 {
-#if !UE_EDITOR	
-	// Only one instance of the game can be initialized!
-	const UGeneralProjectSettings& ProjectSettings = *GetDefault<UGeneralProjectSettings>();
-	const FString LockFilePath = FPlatformProcess::UserTempDir() + ProjectSettings.ProjectID.ToString();
-	if (!IFileManager::Get().CreateFileWriter(*LockFilePath, 0) && bIsEnabled)
-	{
-		FPlatformApplicationMisc::RequestMinimize();
-		FPlatformMisc::RequestExit(0);
-	}
+#if !UE_EDITOR
+	FCoreDelegates::OnAllModuleLoadingPhasesComplete.AddLambda([bIsEnabled]() 
+	{	
+		// Only one instance of the game can be initialized!
+		const UGeneralProjectSettings& ProjectSettings = *GetDefault<UGeneralProjectSettings>();
+		const FString LockFilePath = FPlatformProcess::UserTempDir() + ProjectSettings.ProjectID.ToString();
+		if (!IFileManager::Get().CreateFileWriter(*LockFilePath, 0) && bIsEnabled)
+		{
+			FPlatformApplicationMisc::RequestMinimize();
+			FPlatformMisc::RequestExit(0);
+		}
+	});
 #endif
 }
 

Source/CheckAppInstance/Public/CheckAppInstanceBPLibrary.h

@@ -4,8 +4,9 @@
 
 #include "Kismet/BlueprintFunctionLibrary.h"
 #include "HAL/FileManager.h"
-#include "Runtime/ApplicationCore/Public/Windows/WindowsPlatformApplicationMisc.h"
+#include "HAL/PlatformApplicationMisc.h"
 #include "GeneralProjectSettings.h"
+#include "Misc/CoreDelegates.h"
 #include "CheckAppInstanceBPLibrary.generated.h"
 
 UCLASS()