I am currently try to extend a video game with dll injection. While I have no problem injecting my dll, I am unsure how I should handle dependencies of my dll. First I linked them statically. But I read many times it would be better to link them dynamically.
The problem with this is that I don't want to put the dlls into the game folder. But it looks like windows is only looking for the other dlls in the game.exe folder instead of in the folder where my injected dll is.
My guess to solve the problem was to also inject the dependencies before I inject my own dll into the game process with LoadLibraryW. While this seems to work I am unsure if this will work correctly under all circumstances or should I stick with static linking to avoid all that hacky stuff?
Related
My basic issue is this: my program (MyProgram.exe) has a dependency on a DLL from another program (OtherProgram), and I'm trying to avoid repackaging a new DLL every time OtherProgram updates. I'd like to have MyProgram.exe link in OtherProgram's DLL when it launches, but I'm not completely sure that Windows allows for this. So if there is some kind of workaround that would also be acceptable.
And just for some background, the platform is Windows 7 x64, and MyProgram.exe runs fine when I create a symlink in the MyProgram.exe project directory to the DLL in OtherProgram's install directory. When I try to run it without the symlink, I get the "program can't start because OtherProgramDLL.dll is missing from your computer" error.
Any advice or links to relevant info is greatly appreciated!
EDIT: Clarification: the DLL is not linked at compile-time, this issue crops up at runtime
There are two types of dynamic linking in the Windows world:
Load-Time linking is when a DLL is loaded automatically when your program starts up. Windows finds this DLL using a specific algorithm I'll discuss below.
Run-Time linking is when you specifically load a DLL by calling LoadLibrary in your code. Similar rules apply as to how the library is found, but you can specify a fully-qualified or relatively-qualified path to control the search.
In the case of Load-Time linking, MS recommends that your program's DLLs are stored in and loaded from the same directory where your application is loaded from. If this is at all workable, this is probably your best option.
If that doesn't work, there are several other options, outlined here. One is to leverage the search order by putting the DLL in either the working directory or the directory where the application was loaded from.
You can change the working directory of an application by:
Create a shortcut to your application.
Bring up the shortcut's properties
Edit the "Start in" property with the directory where the DLL is located.
When you launch your application using the shortcut, it will load the right DLL.
Other options for load-time linking include:
Adding a manifest to your application which specifies where your dependent assemblies are, or,
Setting the PATH.
You could use LoadLibrary, but you would need a way to guarantee the DLL's location. This Wikipedia article provides good example on how to use the DLL after it has been loaded.
You can add the directory where the dll is located to the PATH environment variable.
I have struggled with the same problem and also found a dead end with the suggested methods like LoadLibrary, SetDllDirectory, Qt's addLibraryPath and others. Regardless of what I tried, the problem still remained that the application checked the libraries (and didn't find them) before actually running the code, so any code solution was bound to fail.
I almost got desperate, but then discovered an extremely easy approach which might also be helpful in cases like yours: Use a batch file! (or a similar loader before the actual application)
A Windows batch file for such a purpose could look like this:
#echo off
PATH=%PATH%;<PATH_TO_YOUR_LIB>
<PATH_TO_YOUR_APP_EXE>
/edit: Just saw #SirDarius comment in Luchian's answer which describes that way, so just take my batch code bit as a reference and all credits go to him.
I have the same problem with one application I am working on.
I do not want to use runtime loading because there are tens of functions I would need to manually create function pointer for.
Mr Dibling's mention of manifest file opened a new door for me but I sadly found out that the oldest version of windows that supports the feature is Windows 7. It won't even work on Vista.
Long story short, a friend familiar with Windows Application development told me to look up Delay-Loaded DLL, which turns out to solve the problem perfectly with minimal effort. It delays the loading of DLL library to either the point you manually do, or the first time its function is called. So you just need to add your DLL path to the search path before that happens, where SetDllDirectory helps.
Here is the steps to make it work:
1) Specify the DLL to be delay-loaded to linker, either through your makefile, cmake or VS property page (Linker->Input of VS2015)
2) Call SetDllDirectory at the beginning of your program, before any call to the DLL is made.
Delay-loaded DLL is supported all the way back to VC6.
SetDllDirectory is supported after XP SP1.
Use Symbolic Links to the 3rd Party Executables
I found the approach advocated by Aaron Margosis useful. See:
Using NTFS Junctions to Fix Application Compatibility Issues on 64-bit Editions of Windows
Essentially, create symbolic links to each of the dependent 3rd Party executables. Place these symbolic link files in and amongst your own dependent executable files. Except for filename changes to the targets, the 'soft' symbolic links will resolve the load-time dependencies even as the target of the links are changed by future updates.
I need to build a DLL that can then be loaded with JNI from a java program. I was able to do this last year and it worked fine. I'm trying to recompile my same .cpp file now though that I make the dll with and it is failing because of an included dll dependency that gets brought in.
I have a c++ program that calls about 5 functions from some existing C++ code here. These functions are part of a huge codebase that are normally all linked together to build a set of 5 dlls.
I use dependency walker to view my dll and last year it compiled with just 2 dependent system dlls being put in my dll. Today I'm trying to recompile the same dll, but it brings in a 3rd dll file if I link with the .lib file from our existing codebase that contains the functions I use.
Basically I know my dll will work fine with JNI if I can avoid that 3rd dll showing up in my program. The problem is I don't know how to reference the functions I need in my code from our existing code base without linking to the lib file.
I can get this to work with standard c++ files and methods. This problem only happens when I reference this preexisting code from our huge codebase.
If I do not link my .obj file with a .lib file from our code I get unresolved reference messages from my Borland 5.5 compiler I have to use.
The overall issue is that my dll file works fine when I call it from a c++ exe file, but Java cannot handle something in it. Also, if I compile my code into a .so file in unix instead of a windows dll, Java JNI works fine and can load it. I know the problem is related to how Windows uses dlls, and I know if this 3rd dll doesn't load as part of my dll it will also work. I just have no idea what I did last year to build my dll without this 3rd one showing as a dependency.
If I comment out the functions from our existing code it compiles fine and loads because the 3rd dll dependency doesn't get put in my dll.
More Details
I had a message about missing _strcopy, so I linked in the cw32mti.lib file and that went away, but then that cw32mti.dll shows up in my dll file. How do I prevent the missing reference message for something like that and prevent it from putting the dll in my dll?
My link command looks like this.
ilink32 mydll.obj, mydll.dll,,cw32mti
The only way I get the other missing references to work is adding the other dll to my link command like:
ilink32 mydll.obj, mydll.dll,,cw32mti.lib other.lib
Where other.dll contains functions I call from mydll.dll such as calculate(int a, int b), so my code has a link it in like calculate(num1, num2); The problem is when I use the lib that contains the calculate method, it also brings in other dlls linked to the other.dll that I do not want to load. I need to be able to call calculate(num1, num2) without adding other.dll to mydll.dll. This worked before without dynamically calling calculate and using the getprocaddress type of coding.
Update - I eventually had to give up on getting the windows dll to work with the smartheap memory manager. Since this code was deployed in unix, I was able to just build the .so files and get those to work with JNI. For the Windows dll compile, I put some conditional compiler statements around the JNI code that was causing the smartheap dll to be loaded, so then when it compiles in windows it does not use that code. Instead I just had it print out a statement saying it was not executing in windows.
We also ran into issues later with getting our 64 bit JBoss server to run and load these 32 bit .so files. I ended up running a parallel JBoss server next to the 64bit one and called the methods that referenced the 32 bit library on the 32 bit instance of JBoss.
It may evolve into more later, but for now this task is working for us after months of trying many different things. I appreciate all of the help and input here.
If you can get your hands on the application DLL built from last year, use TDUMP to see what the module dependencies are. (You might have to analyze all the DLLs to get a good picture.) Then endeavor to reproduce that in the new DLL, probably by adjusting the linker's configuration .DEF file.
Without any code or .DEF file shown in your question, it is very difficult to be more specific.
I'm creating a small cross platform program with C++/wxWidgets. By using static linking I managed to get only one .exe file for Windows in the end. However it still requires a small (18 KB) mingwm10.dll
Although I can just distribute my app with this dll, I'd prefer to have it "inside" the .exe... Is it possible?
Thanks
If you use the configure script to compile wxWidgets, add --disable-threads. This will set wxUSE_THREADS to 0, wxThread class and all the code that depends on threads will not be compiled. Automatically mingwm10.dll will not be linked.
The "single EXE that includes all project files" is called a setup script. Consider something like InnoSetup, or MSI.
Rolling your own install DLL on first use code is theoretically possible, but extremely ugly. It gomes like this: you add the DLL (zipped, if possible) to the EXE as resources. On startup, you try to load the DLL; if you cannot, you take it from the resources and place somewhere. And that will break under non-admin user. And the automatic privilege escalation won't work (it works for setup files). And you have to be very careful not to call anything in the DLL before you install it. Like I said, very, very ugly.
I am working on a Qt DLL that is used as a plugin for a large application. This DLL depends on other DLLs that are sadly not located in the same folder and hence will only load if the current working directory has been set correctly (which the large application does prior to calling LoadLibrary on the DLL). I have no control over this behaviour.
I have been asked to add a simple COM object to this plugin which I have done but I now have the problem that the DLL cannot be registered or used by a 3rd-party application unless the current working directory is set correctly - because any LoadLibrary calls on the plugin fail due to the missing dependencies. Obviously I have no control over the current working directory used by 3rd-party apps and at this stage I am not allowed to modify the PATH to ensure the dependencies can be found.
I have tried using /DELAYLOAD for the dependent DLLs but this fails with 'cannot delay-load foo.dll due to import of data symbol...' errors. Again, I cannot easily change the way these dependent DLLs are used.
Currently I think the only solution is to move the COM object into a stand-alone DLL that doesn't depend on anything else but I am under pressure to find a solution and leave the COM object in the plugin DLL. I can't see how this is possible so I thought I'd see if anyone else has any ideas. Some form of system-wide SetDllDirectory call would help or some registry hack that could set the working directory when a 3rd-party app calls LoadLibrary on my plugin.
IMO separating the COM object into a separate .dll is the cleanest solution - anyone would expect an in-proc COM server to be registered by using regsvr32 and that requires no fancy dependencies in that COM server.
I don't know if it's precisely a solution to your problem, but maybe this can help you: try to look at the possibilities offered by manifest files. I hope it will help.
You could use a runtime registration model.
The Dll could register itself as a COM server in its own initialisation code.
This only requires that loadlibrary is guaranteed to be called before the dll is used as a COM server.
I am writing a DLL to plug into another (3rd party) application. The DLL will need to depend on another set of DLLs (for license reasons I cannot link statically).
I would like my DLL to be "xcopy-deployable" to any directory. I would also like not to require adding this directory to the path.
If I just build the DLL the usual way, Windows will refuse to load the DLL, since it cannot find the DLLs next to the current process.
Are there any good options for helping Windows locate the DLL?
To answer some questions:
The DLL is written in C++.
The extra DLLs are QT-dlls.
I would like to place the extra DLLs in the same folder as my plugin DLL. I can get the name of that folder from GetModuleFileName.
The application is Firefox, the DLL is a PKCS#11 security module.
The application loads the DLL using the full path to the DLL (the user supplies it when installing the plugin).
Requiring that the DLLs be placed in System32 or next to the application would work, but it is a bit messy and could cause problems with uninstallers.
LoadLibrary and GetProcAddress would of course work, but is not really feasible in my case. I am using hundreds, if not thousands, of methods in the other DLLs. I really need to use the import-libraries.
I had thought about using delay-loaded dlls combined with SetDllDirectory in DllMain. Have anyone tried anything like this?
I can think of 3 ways.
put the dlls in the same folder as your application (you cannot do this?)
Use runtime linking. LoadLibrary() and GetProcAddress()
Use a manifest http://msdn.microsoft.com/en-us/library/aa374182(VS.85).aspx
But if the dll isn't in the same folder as the .exe, how are you going to know where it is? forget Windows not knowing, how do you know?
you can specify the path of dll as the parameter of LoadLibrary().
Another option is to modify the PATH variable. Have a batch file for launching the main app, and set the PATH=%PATH%;%~dp0. This ensures a minimal footprint, with no additional traces left in the system after running.