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How to get used dll's path information programetically?

litu kumar6-Nov-12 19:38

6-Nov-12 19:38

Hi,
I'm using a .net dll in a Win32 application.
I want to print the DLL file location programetically.

I tried like as below , but it still displaying the EXE's (generated by my win32 app.) path -
-----------------------------------------------------------
HMODULE hmod = GetModuleHandle(TEXT("MyApp.dll"));
TCHAR szPath[MAX_PATH + 1] = {0};
DWORD dwLen = GetModuleFileName(hmod, szPath, MAX_PATH);
wprintf(L"CURRENT DIRECTORY: %s\n" ,szPath);
-----------------------------------------------------------

Please advice any new solution or any correction required (above code stuff) for the same.

Re: How to get used dll's path information programetically?

Richard MacCutchan6-Nov-12 21:40

Richard MacCutchan

6-Nov-12 21:40

The chances are that hmod is NULL because MyApp.dll has not been loaded into memory as required by the GetModuleHandle()[^] function. Always check return values from API calls, do not just assume that it works.

One of these days I'm going to think of a really clever signature.

Re: How to get used dll's path information programetically?

litu kumar6-Nov-12 23:27

litu kumar

6-Nov-12 23:27

Hi Richard,

You mean to initialize 'hmod' to NULL as below -

HMODULE hmod =NULL;
hmod= GetModuleHandle(TEXT("MyApp.dll"));
if(hmod!=NULL)
{
DWORD dwLen = GetModuleFileName(hmod, szPath, MAX_PATH);
wprintf(L"CURRENT DIRECTORY: %s\n" ,szPath);
}
====================================
If the above code stuff as per your indication,then 'GetModuleHandle' not returning NULL .
And it printing the path of EXE not of required 'MyApp.dll'

Kindly guide me if i understood the wrong thing.

modified 7-Nov-12 6:38am.

Re: How to get used dll's path information programetically?

Richard MacCutchan7-Nov-12 4:54

Richard MacCutchan

7-Nov-12 4:54

No, I mean the value returned from GetModuleHandle() is NULL if that library has not been loaded into your address space. In which case you will get the path of your executable. Check the link to the documentation that I gave you.

One of these days I'm going to think of a really clever signature.

Re: How to get used dll's path information programetically?

litu kumar7-Nov-12 17:11

litu kumar

7-Nov-12 17:11

Hi Richard,

I'm beginner to this area. I also gone through that document you sent me and got some idea.
But unable to conclude any way to get information on loaded DLL.

Actual requirement is to get both Dll's - "physical location" & "Version" information programeically from a Win32(vc++) application.

I tried 2-3 ways but still failing to fulfill my requirement.

Kindly share a detailed way or code then it will great to learn.

Re: How to get used dll's path information programetically?

Richard MacCutchan7-Nov-12 21:34

Richard MacCutchan

7-Nov-12 21:34

As I said before, you must load the DLL first, using the LoadLibrary()[^] function. Only then can you get the full path details. As to version information, you need the Version Information Functions[^].

One of these days I'm going to think of a really clever signature.

Re: How to get used dll's path information programetically?

litu kumar7-Nov-12 22:35

litu kumar

7-Nov-12 22:35

Thanks Richard,

Its working fine by using LoadLibrary().
Extracting the DLL's version info - i have check.

Mean while for my knowledge purpose ,can you please clarify one doubt.

Even though we are adding DLL reference through project-proporties, why it was still printing the application's Exe path (please refer the code stuff in my last reply) ??

Thanks

Re: How to get used dll's path information programetically?

Richard MacCutchan8-Nov-12 0:16

Richard MacCutchan

8-Nov-12 0:16

litu kumar wrote:
why it was still printing the application's Exe path

I have already explained twice. If the DLL has not been loaded into your application's address space then the call to GetModuleHandle() will return NULL; something that you have not catered for in your code. If the module handle is NULL then GetModuleFileName() will return the path of your executable program. The sequence you should follow is:

C++

HMODULE hmod = LoadLibrary(TEXT("MyApp.dll"));
if (hmod != NULL)
{
    TCHAR szPath[MAX_PATH + 1];
    DWORD dwLen = GetModuleFileName(hmod, szPath, MAX_PATH);
    if (dwLen > 0)
    {
        wprintf(L"CURRENT DIRECTORY: %s\n" ,szPath);
    }
    else
    {
        // check GetLastError() for reason
    }
}
else
{
// display error message
}

One of these days I'm going to think of a really clever signature.

Re: How to get used dll's path information programetically?

litu kumar8-Nov-12 2:58

litu kumar

8-Nov-12 2:58

Thanks Richard for above information.

I have a small doubt, kindly clarify -

What is the difference between 'Adding the DLL reference from Project-properties' & 'LoadLibrary(MyApp.dll)' ??

-I mean in each case, how Dlls are being loaded (Dynamically\Statically)

"Adding the DLL reference from Project-properties " means - Right click on Project name -> Referenceses ..->Add New Reference... Then select 'MyApp.dll' from existing directory.

I can guess my answer but not sure. Thats why please ensure me.

Thanks

modified 8-Nov-12 9:07am.

Re: How to get used dll's path information programetically?

Richard MacCutchan8-Nov-12 4:03

Richard MacCutchan

8-Nov-12 4:03

I have never used dll's by adding to the project references; are you sure we are talking about C++ here? They are either linked in by adding the reference in the Linker properties of your project, or loaded dynamically by the LoadLibrary() function. Which version of Visual Studio are you using?

One of these days I'm going to think of a really clever signature.

Re: How to get used dll's path information programetically?

litu kumar15-Nov-12 19:53

litu kumar

15-Nov-12 19:53

I'm trying to use another DLL from my Win32 dll.
So we can use external dll in either way.

why i asked that question , because if that external dll having different versions in same system.Then which version its taking while loading.

Actually one client requirement is there -
Our application should load this external DLL irrespective of certain DLL-location.

In above both ways[Adding reference AND LoadLibrary()] of DLL loading ,we are explicitly giving a DLL location Or placing the DLL in the same project location.

IS there any way we can make DLL to load independently(we'll not give explicit dll location or DLL itself).

Thanks

Re: How to get used dll's path information programetically?

Richard MacCutchan15-Nov-12 23:50

Richard MacCutchan

15-Nov-12 23:50

I'm not sure I fully understand what you are asking. However, you can include a library in your build process by adding the .LIB file to the linker input. This will add a reference to the associated DLL to the final program. At execution time the system will load the DLL when necessary, by searching for it in the standard library directories. If you wish to load it yourself using the LoadLibrary() function, then you can provide just the name, in which case the system will search for it as before, or you can provide the full path to an alternate version that you have installed elsewhere.

One of these days I'm going to think of a really clever signature.

Re: How to get used dll's path information programetically?

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