We are trying to load a dll-library from inside a 64-bit dll using LoadLibraryA function. It returns 126 error - mod not found. The dll file path given to the function is correct, we are sure.
We have tried a dummy dll to test and it worked, it is loaded.
We also tried adding the dll (which is a dependcy of the first dll that we want to load) to the dummy dll. It also worked. So the problem seems not about the dependency dlls, but the original dll that we want to load in the first place.
We also tried converting the dl to 64-bit, and tried that, still no good.
We also checked the dependencies with Dependency Walker. Everything is OK.
The operating system that we are using is Windows 8, 64bit. If it makes any difference..
Does anyone have any idea about this poblem?
EDIT:
We also tried this code:
hModule = LoadLibraryW(L"C:\\temp\\dllToLoad.dll");
and received this error code:
"First-chance exception at 0x00000000 in C_Test_TSMPPKCS11.exe: 0xC0000005: Access violation at location 0x0000000000000000."
EDIT 2:
The code that we used in the first place is:
hModule = LoadLibraryA((char*)aDLLFile);
EDIT 3:
We are using complete path to load the dll. In order to test this we tried this code:
FILE *fp;
int size = 0;
fp=fopen("C:\\temp\\dllToLoad.dll", "r");
size = fgetc(fp);
printf("size:%d\n",size);
fclose(fp);
There was no problem, we received the file size which is 77.
We also tried converting the dl to 64-bit, and tried that, still no good.
There's no way you can load a 32-bit dll as executable code into a 64-bit process (and since you're using LoadLibraryA() that's all you can be trying to do).
Assuming the dll that you are trying to load and the process that you're loading it into are the same type then are you passing a complete path to LoadLibraryA() or a relative path or just a dll name? If you're not using a complete path then consider using LoadLibraryEx() if possible as this gives you much more control over the search path used. If you are using a complete path try opening the file using normal file operations if you fail to load the dll, does this work? If that works then try LoadLibraryEX() with LOAD_LIBRARY_AS_DATAFILE and see if that will load the dll as a simple data file (which proves that it's finding the file).
Run up Sysinternal's ProcMon and watch the code open the DLL, that may show you dependent DLL load failures.
Related
I want to load DLL from sub folder of my application folder. So I put my.dll with all dependant dlls to /myfolder
I takes me a while to figure out the correct way to load it:
m_handle = LoadLibraryEx(".\\myfolder\\my.dll", 0, LOAD_WITH_ALTERED_SEARCH_PATH);
It works very well on Windows 7 & and later. However it returns error 998 ERROR_NOACCESS “Invalid access to memory location.” On Windows XP.
However loading this dll from the application folder works very well on all versions of Windows
PS: I tried to use SetDllDirectory with absoulte and relative paths to myfolder, but still no success on Windows XP
MSDN has this to say about the LOAD_WITH_ALTERED_SEARCH_PATH flag:
If this value is used and lpFileName specifies a relative path, the
behavior is undefined.
If you don't need to use the alternative search strategy, you can just pass 0 as the flags parameter. If you really need this flag then you must call GetFullPathName first to get the absolute path.
as we all know when we start a CMD.exe it will appear a console window and start with lines like:
Microsoft Windows [版本 6.1.7601]
版权所有 (c) 2009 Microsoft Corporation。保留所有权利。
C:\Users\hey>
but when i crate a windows console project in VS and my code like this:
int _tmain(int argc, _TCHAR* argv[])
{
auto h = LoadLibrary(__TEXT("cmd.exe"));
Sleep(99999);
}
just turns out a black window.no lines out!
as i expect，i can load this PE(windows executable format) file in my process so i do not have to start a new cmd.exe and redirect its stdIO to the process which start cmd.exe.(i know Loadlibrary with an exe file could start a exe in calling process without creating a new process)
and why is Loadlibrary not working?(it did not appear any words in the console window)
(i know Loadlibrary with an exe file could start a exe in calling process without creating a new process)
No, it can't.
You can pass the name of an EXE file to LoadLibraryEx if you use the LOAD_LIBRARY_AS_DATAFILE flag, in order to access its resources, but LoadLibrary neither runs the code in an EXE nor prepares the code for being run.
The entry point for an EXE is designed for having its own process. (I'm talking about the real entry point, which is usually provided by a language support library. It may have a name such as wmainCRT and its address, not the address of user-provided main(), appears in the PE header). Typically it exits by calling ExitProcess(), which will have catastrophic effects on your host EXE even if you do manage to map it into your memory space and call it.
The requirements for the entry point of a dynamically loadable library and an executable file are very, very different.
You can't run an executable via LoadLibrary. Use CreateProcess (or one of its siblings) instead.
From the LoadLibrary function docs (highlight in bold is mine):
LoadLibrary can also be used to load other executable modules. For example, the function can specify an .exe file to get a handle that can be used in FindResource or LoadResource. However, do not use LoadLibrary to run an .exe file. Instead, use the CreateProcess function.
I have a process which calls CreateProcess. It appears that CreateProcess returns nonzero indicating success. However, the HANDLE to the process then gets immediately set, indicating the process has exited. When I call GetExitCodeProcess, STATUS_DLL_NOT_FOUND is then returned.
I understand that a DLL is missing. I even know exactly which one. However, what I don't understand is how to figure that out programmatically.
I noticed that Windows will present a dialog saying that the process failed to start because it couldn't find the specified DLL (screenshot: http://www.mediafire.com/view/?kd9ddq0e2dlvlb9 ). In the dialog, Windows specifies which DLL is missing. However, I find no way to get that information myself programmatically.
If a process fails to start and would return STATUS_DLL_NOT_FOUND, how do I programmatically retrieve the library name to which the target process was linked which couldn't be found? That way I can automatically record in an error report what DLL appears to be missing or corrupt in a given installation.
CreateProcess returns 0 indicating success.
CreateProcess() returns a BOOL, where 0 is FALSE, aka failure not success.
If a process fails to start and would return STATUS_DLL_NOT_FOUND, how do I programmatically retrieve the library name to which the target process was linked which couldn't be found?
Unfortunately, there is no API for that. Your only option would be to manually access and enumerate the executable's IMPORTS table to find out what DLLs it uses, and then recursively access and enumerate their IMPORTS tables, manually checking every DLL reference you find to see whether that DLL file exists on the OS's search path or not.
If the dll is statically linked you can walk the iat and see if the dll exists. If the dll is dynamically loaded then starting the process suspended and hooking LoadLibrary (or instead of hooking emulate a debugger) is the only way I see.
The best way is to use loader snaps. Basically you use gflags.exe (which is included with windbg) to enable loader snaps; then, run the process with the debugger attached. Loader snaps will enable the loader to print out dbg messages of the process and it will print the failures.
gflags.exe -i yourcode.exe +sls
windbg yourcode.exe
I know this is not a "programmatic" way to find out the problem, but what the loader does is complicated, and you don't really want to be redoing its logic to find the failure. That is why loader snaps were invented.
The very hard way would be: Parsing the .EXE and .DLL files and create the dependency tree of .DLL files.
I don't think there is a way to get a list of DLL files that are missing: When Windows finds one missing DLL file it stops loading so if one DLL file is missing you won't find out if more DLL files are missing.
Another problem you could have is that old DLL versions could have missing "exports" (functions). This is even harder to detect than the dependency tree.
Just since this is somehow the top stackoverflow result on Google for "STATUS_DLL_NOT_FOUND". How to trace and solve any random occurence:
Download SysInternals procmon64.exe (or just the entire set). After startup immediately hit the looking glass 'Stop capture' button (Ctrl+E). And 'Clear' (Ctrl+X).
Set filters for:
'Process name' is to whatever the mentioned process name was (for me it was 'build-script-build.exe') [Add]
'Result' is not 'SUCCESS' [Add]
'Path' ends with '.dll' [Add] [OK]
Start capture again (Ctrl+E).
Run the thing that had a problem again (for me: build cargo). Google for the last listed DLL file.
For me that was VCRUNTIME140.dll, so I installed the VC++ 2015 to 2019 redistributable.
ProcMon is kind of like unix strace.
I'm writing a wrapper program that loads Winamp input plugins. I've got it working well so far with quite a few plugins, but for some others, I get an error message at runtime when I attempt to call LoadLibrary on the plugin's DLL. (It seems to happen mostly with plugins that were included with Winamp.) A dialog appears and gives me the error code and message above. This happens, for example, with the in_flac.dll and in_mp3.dll plugins (which come with Winamp). Any ideas on how I can remedy this situation?
EDIT:
This basically iterates through the plugins in a directory and attempts to load and then free each one. Some plugins produce the error I mentioned above, while others do not.
wstring path = GetSearchPath();
FileEnumerator e(path + L"in_*.dll");
while(e.MoveNext()) {
wstring pluginPath = path + e.GetCurrent().cFileName;
MessageBoxW(NULL, pluginPath.c_str(), L"Message", MB_OK);
HINSTANCE dll = LoadLibraryW(pluginPath.c_str());
if(!dll) {
pluginPath = wstring(L"There was an error loading \"") + wstring(e.GetCurrent().cFileName) + L"\":\n" + LastErrorToString();
MessageBoxW(NULL, pluginPath.c_str(), L"Error", MB_OK);
continue;
}
FreeLibrary(dll);
}
Starting from Visual Studio 2005, the C/C++ runtime MUST be put in the Windows side-by-side cache (C:\windows\WinSxS), so putting the CRT DLL's next to your exe doesn't work anymore (with one exception, see later).
You MUST also refer to the CRT DLL's via a manifest file. This manifest file is generated by the linker and will have a name like myexe.exe.manifest or mydll.dll.manifest. Distribiute this manifest with your application/DLL or link it in the exe/dll using the mt command.
The side-by-side cache and the manifest file system were introduced in Windows XP and are mainly intended to solve the DLL hell and to increase security.
Not referring to the CRT using a manifest or not putting the CRT in the side-by-side cache will generate error 6034.
If you still want to put the CRT DLL's next to your application, you could also use private assemblies, which means creating a kind of mini-side-by-side cache in the folder of your application. You can find additional information on MSDN.
there can be many reason... put your code here for clarification... one of the many solution might be is
Rebuild your application with a manifest. Building an application with Visual Studio automatically puts the manifest into the resulting EXE or DLL file. If you are building at the command line, use the mt.exe tool to add the manifest as a resource. Use resource ID 1 if building an EXE, 2 if building a DLL.
Also, you may try adding this into the code:
#pragma comment(linker,"/manifestdependency:\"type='win32' name='Microsoft.VC90.CRT' version='9.0.21022.8' processorArchitecture='x86' publicKeyToken='1fc8b3b9a1e18e3b'\"")
I'm including python.h in my Visual C++ DLL file project which causes an implicit linking with python25.dll. However, I want to load a specific python25.dll (several can be present on the computer), so I created a very simple manifest file named test.manifest:
<?xml version='1.0' encoding='UTF-8' standalone='yes'?>
<assembly xmlns='urn:schemas-microsoft-com:asm.v1' manifestVersion='1.0'>
<file name="python25.dll" />
</assembly>
And I'm merging it with the automatically embedded manifest file generated by Visual Studio thanks to:
Configuration Properties -> Manifest Tool -> Input and Output -> Additional Manifest Files
-->$(ProjectDir)\src\test.manifest
python25.dll is now loaded twice: the one requested by the manifest, and the one that Windows should find through its search order.
Screendump of Process Explorer http://dl.dropbox.com/u/3545118/python25_dll.png
Why is that happening and how can I just load the DLL file pointed by the manifest?
After exhaustive battle with WinSxS and DLL redirection, here's my advice for you:
Some background
Various things can cause a DLL file to be loaded under Windows:
Explicit linking (LoadLibrary) -- the loader uses the current activation context of the running EXE file. This is intuitive.
Implicit linking ("load time linkage", the "auto" ones) -- the loader uses the default activation context of the depending DLL file. If A.exe depends on B.dll depends on C.dll (all implicit linkage), the loader will use B.dll's activation context when loading C.dll. IIRC, it means if B's DllMain loads C.dll, it can be using B.dll's activation context -- most of the time it means the system-wide default activation context. So you get your Python DLL from %SystemRoot%.
COM (CoCreateInstance) -- this is the nasty one. Extremely subtle. It turns out the loader can look up the full path of a DLL file from the registry using COM (under HKCR\CLSID). LoadLibrary will not do any searching if the user gives it a full path, so the activation context can't affect the DLL file resolution. Those can be redirected with the comClass element and friends, see [reference][msdn_assembly_ref].
Even though you have the correct manifest, sometimes someone can still change the activation context at run time using the Activation Context API. If this is the case, there is usually not much you can do about it (see the ultimate solution below); this is just here for completeness. If you want to find out who is messing with the activation context, WinDbg bp kernel32!ActivateActCtx.
Now on to finding the culprit
The easiest way to find out what causes a DLL file to load is to use Process Monitor. You can watch for "Path containing python25.dll" or "Detail containing python25.dll" (for COM lookups). Double clicking an entry will actually show you a stack trace (you need to set the symbol search paths first, and also set Microsoft's PDB server). This should be enough for most of your needs.
Sometimes the stack trace obtained from above could be spawned from a new thread. For this purpose you need WinDbg. That can be another topic, but suffice to say you can sxe ld python25 and look at what other threads are doing (!findstack MyExeModuleName or ~*k) that causes a DLL file to load.
Real world solution
Instead of fiddling with this WinSxS thing, try hooking LoadLibraryW using Mhook or EasyHook. You can just totally replace that call with your custom logic. You can finish this before lunch and find the meaning of life again.
[msdn_assembly_ref]: Assembly Manifests
I made some progress for the understanding of the issue.
First let me clarify the scenario:
I'm building a DLL file that both embeds and extends Python, using the Python C API and Boost.Python.
Thus, I'm providing a python25.dll in the same folder as my DLL file, as well as a boost_python-vc90-mt-1_39.dll.
Then I have an EXE file which is a demo to show how to link to my DLL file: this EXE file doesn't have to be in the same folder as my DLL file, as long as the DLL file can be found in the PATH (I'm assuming that the end user may or may not put it in the same folder).
Then, when running the EXE file, the current directory is not the one containing python25.dll, and that's why the search order is used and some other python25.dll can be found before mine.
Now I figured out that the manifest technique was the good approach: I managed to redirect the loading to "my" python25.dll.
The problem is that this is the Boost DLL file boost_python-vc90-mt-1_39.dll that's responsible for the "double" loading!
If I don't load this one, then python25.dll is correctly redirected. Now I somehow have to figure out how to tell the Boost DLL file not to load another python25.dll...
Dependency Walker is usually the best tool for resolving this kind of problem. I'm not too sure how well it handles manifests though...
Where in this entangled mess is the actual process executable file?
Two possibilities come to mind:
You are writing a Python extension DLL file. So the Python process is loading your DLL file, and it would already have its own python25.dll dependency.
The EXE file loading your DLL file is being built with header files and libraries provided by the DLL file project. So it is inheriting the #pragma comment(lib,"python25.lib") from your header file and as a result is loading the DLL file itself.
My problem with the second scenario is, I'd expect the EXE file, and your DLL file, to be in the same folder in the case that the EXE file is implicitly loading your DLL file. In which case the EXE file, your DLL file and the python25.dll are all already in the same folder. Why then would the system32 version ever be loaded? The search order for implicitly loaded DLL files is always in the application EXE file's folder.
So the actual interesting question implicit in your query is: How is the system32 python26.dll being loaded at all?
Recently, I hit a very similar problem:
My application embedding Python loads the python32.dll from a known location, that is a side-by-side assembly (WinSxS) with Python.manifest
Attempt to import tkinter inside the embedded Python interpreter caused second loading of the very same python32.dll, but under a different non-default address.
The initialisation function of tkinter module (specifically, _tkinter.pyd) was failing because to invalid Python interpreter thread state (_PyThreadState_Current == NULL). Obviously, Py_Initialize() was never called for the second Python interpreter loaded from the duplicate python32.dll.
Why was the python32.dll loaded twice? As I explained in my post on python-capi, this was caused by the fact the application was loading python32.dll from WinSxS, but _tkinter.pyd did not recognise the assembly, so python32.dll was loaded using the regular DLL search path.
The Python.manifest + python32.dll assembly was recognised by the DLL loading machinery as a different module (under different activation context), than the python32.dll requested by _tkinter.pyd.
Removing the reference to Python.manifest from the application embedding Python and allowing the DLL search path to look for the DLLs solved the problem.