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two simple questions

Posted on 1999-07-23
Medium Priority
Last Modified: 2013-12-03
1:There is a globle variable "A" in a .DLL ;
In my .EXE, I also have a int variable "B" that have a meaningful content.Now,I load the .dll and I want to put the B's content into A;like B=A;How can I achieve?
If I write B=A in my .EXE,there will be unsolved error for "A".
How can I transport variable content between .dll and .exe?

2.Is .DEF necesaary for a .DLL which I want to export a few functions from .Are there other ways?

3.I have get a handle of a window and I want to get the threadID of it.I use GetWindowThreadProcessId() but I dont know what should be put in the second param.

Really hope somebody expert can help me.

Question by:SFS
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Author Comment

ID: 1403633
Edited text of question.

Author Comment

ID: 1403634
Adjusted points to 150

Accepted Solution

rocket96 earned 600 total points
ID: 1403635
1. Use shared memory. Search MSDN for "shared memory". I have soure lying around, but I'll have to dig around for it. Lemme know if you need it.

2. Use __declspec( dllexport ) to export functions.

3. If you have a DWORD as the thread ID, pass a pointer to it:

DWORD threadID;
GetWindowThreadProcessID( hWnd, &threadID );
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Author Comment

ID: 1403636
Thank you,rocket96.
1.The so called "share memory" is meant to be shared between the .exe that load the .dll and the .dll ,right?
would you please give me a simple but concrete example ,just like make A=B(A in .dll and B in .exe).

BTW:I'm very urgent for the answer.I 'm writing a critical and very important homework and I will send in it tomorrow that is deadline!:)

2.I add the __declspec( dllexport) before my function FUNC which  in my .dll and I compile it successfully.Then,in the .exe ,I use LoadLibrary() first,it succeed. When I use Loadprocaddress() in my .exe,It return NULL,wrong! Should I add something else to my .exe? I import it correctly if I use a .DEF file to export that function.  

3.Thank you,I succeed.
But I'm so curious that ,originally,I use these words to do but failed.
LPDWORD pthreadid;

Now I change as you said, but what the difference?


Expert Comment

ID: 1403637
1. Sorry, didn't read your question properly. If you want B=A where B is in the DLL and A is in the exe, then just have a function which the exe can call into the DLL to set B. I can't explain more becuase its a homework question and we're not allowed to answer homework questions.

2. When you use __declspec( dllexport ), you should get an import library which your exe links against. There's no need to call LoadProcAddress() unless you don't have an import library.

3. You declared a pointer which was not allocated. And then you dereferenced an unallocated pointer. Thats not legal.

Expert Comment

ID: 1403638
1:OK,that's enough,thanks
So,you misunderstand and what is "shared memory",when should I use? would you tell me?(This is not homework question:)

2.So,if I want to use LoadProcAddress() to import a function that in a .dll.I must write a .DEF?


Expert Comment

ID: 1403639
BTW:I have send in my homework as I said last time.
I fail and I don't know how to make A=B.How I declare B(in .dll) in .exe?


Author Comment

ID: 1403640
Woo,what's the problem why Babyworship say that?


Expert Comment

ID: 1403641
If B is in a DLL, and A is in an exe, and you want to do:
1. A = B
Export a function in your dll, say GetB(), which returns the value of B. Then your exe code can have:
A = GetB();
Where GetB() is exported from the dll.

2. B = A
This is a little trickier. You can use "shared memory" or memory mapped files, but these techniques are more advanced. Alternatively, you can export a function in your DLL called SetB( argument ); and call it in your EXE like this:

SetB( A );

To use LoadProcAddress, you don't need a def. You should be able to do it with __declspec( dllexport ). I was able to get this to work...

Author Comment

ID: 1403642
1...>>You can use "shared memory" or memory mapped files

I think those two tech are all used to share memory between different processes.But a .dll is in the same process of the .exe.Why you said  I can make use of them to make B=A?(B in .dll,A in .exe)?

2...I still failed even I add the __declspec(dllexport);But originally I succeed if I add a .def,here is my code.

In .exe:

hinstDLL = LoadLibrary((LPCTSTR) "xx.dll");  
hp = (HOOKPROC)GetProcAddress(hinstDLL, "Proc");

The "hp" return NULL,if I compile .dll with a .def


It is ok ...

In .dll:
__declspec(dllexport) LRESULT CALLBACK Proc(int nCode, WPARAM  wParam, LPARAM  lParam );
//declaration,I add what you said.
LRESULT CALLBACK Proc(int nCode, WPARAM  wParam,  
                                LPARAM  lParam  


Could you find some things wrong?

Expert Comment

ID: 1403643
1. If you use memory mapped files or shared memory, then you can say B=A or A=B with either variables in an exe or a dll.

2. If the return value from GetProcAddress() is NULL, use GetLastError() to check the last error.

Author Comment

ID: 1403644
2.I use the GetLastError() and It return 126,it's  ERROR_MOD_NOT_FOUND :
The specified module could not be found.

The loadlibrary is ok,why?


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