Difference between DLL and LIB.? error reasons by using DLL file instead of LIB file?

Question

 

Is there anybody who can explain me?

I am trying for using DLL file from MFC application by using the procedures of the following web link.
http://www.functionx.com/visualc/libraries/staticdll.htm
I can run successfully my tested program by adding LIB file into my project. (the author's direction)
When I added DLL file into my project and run again, I got the error associated with this declaration "extern "C" __declspec(dllimport)void BoxProperties(double L, double H, double W, double& A, double& V);"
If I want to add only DLL file into MFC application, how can I change the code.
My problem is I can download only DLL file not LIB for my real project.
If you have time, I also would like to know what the main difference between LIB and DLL files is.
Because, I wonder " the project can run for adding LIB but show error for using DLL."

Thank you very much for reading my question.

Answer 1

1- using static links the final code in library is integrated with your executable, so the file will be bigger
2- each time you run the program, all library content will be loaded to memory again
3- if you make changes to the library yo need to recompile all the code, not just the library
4- for the error be sure the dll file is in the same executable path or the dll location could be referenced  from the path environment variable ( by exampl in Windows\System32)

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Juan Carlos Ruiz

Answer 2

Dear Expert,

Thank you for you explaination about lib file.

How about the dll file?

I have copied two files dll and lib into my application folder.
I got error message after pressing Ctrl+F5 by adding my DLL file from "Project -> Add to Project -> Files".
But why the project works well after pressing Ctrl+F5 by adding my LIB file from "Project -> Add to Project -> Files".

I would like to know that the example project is compactible only for adding lib?? not for dll.??

if I want to add/use dll file into my MFC application, could i follow the same ways mentioned in the http://www.functionx.com/visualc/libraries/staticdll.htm web page.

Answer 3

How could I correct my errors?? 

 

I compare my steps for trying with both LIB and DLL files. Kindly give me some solutions to overcome it.

Working well...
1: follwed the setps according to the infrormation from http://www.functionx.com/visualc/libraries/staticdll.htm. (For MFC )
2: but inside MFC, I add "LIB" file Project->Add to Project->Files.

Got error...
1: follwed the setps according to the infrormation from http://www.functionx.com/visualc/libraries/staticdll.htm. (For MFC )
2: but inside MFC, I add "DLL" file Project->Add to Project->Files.
3: I also put the DLL into System32.

The eorror is like that...
Linking...
14_10_V5Dlg.obj : error LNK2001: unresolved external symbol __imp__BoxProperties
Debug/14_10_V5.exe : fatal error LNK1120: 1 unresolved externals
Error executing link.exe.

14_10_V5.exe - 2 error(s), 0 warning(s)

Answer 4

Hi,
i'm not an expert (i would like it), i'm just triying to help.

Try setting this, put the dinamic library( dll) name in the yellow mark




If you do that, yo don't need to make any more, just to call the method by name.

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Juan Carlos Ruiz

Answer 5

Hi, excuseme, maybe i'm just causing confussion to you, try to follow this links...

http://msdn.microsoft.com/en-us/library/9yd93633.aspx

Why dll's

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Juan Carlos Ruiz

Answer 6

Hello Dear,
Thank you for giving suggestion for putting dll name as an input file..
But I still can't solve my error.
My error is like that:

Linking...
14_10_V6Dlg.obj : error LNK2001: unresolved external symbol __imp__BoxProperties
Debug/14_10_V6.exe : fatal error LNK1120: 1 unresolved externals
Error executing link.exe.

14_10_V6.exe - 2 error(s), 0 warning(s)

I tried to give "additional library path" not only DLLname but also C:\Program Files\Microsoft Visual Studio\MyProjects\14_10_V6\DLLname.

Is there any other place for changing setting to solve my problem?

Thanky you so much for giving your time..

Regards.

Answer 7

 Thank you very much for the http://msdn.microsoft.com/en-us/library/9yd93633.aspx link.
Now, I know my problem for my real project,
1)I can not use Implicit Linking as I don't have LIB file.(I have only DLL file).
2)I can not use Explicit Linking as I even can't clear my errors for my tested project.. !_!

If you know the good and complete website link for using DLL files from MFC application, kindly share me please..

Thank you very much for your help.
Regards.

Answer 8

are you sure this :
__declspec(dllimport)void BoxProperties(double L, double H, double W, double& A, double& V);

is not

__declspec(dllimport)void BoxProperties(double L, double H, double W, double* A, double* V);

?


see you, i need to sleep,

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Juan Carlos Ruiz

Answer 9

Hi Dear,
I think the code should be correct as I copied and tried all the things from http://www.functionx.com/visualc/libraries/staticdll.htm.
Anyway, thank you for helping me for solving my problem.

Have a nice and sound sleep .. :D

See you later..
With Regards.