Linking to Windows DLL

[DanH]

I need to build an app that uses SQLCipher. I need to link the SQLCipher static lib to a Windows DLL (advapi32.dll) to access the Windows encryption facilities. I'd like to do this all in Qt.

A) Do I have a ghost of a chance of pulling this off? (I have 40 years programming experience in a dozen different languages but essentially no Windows programming experience.)

2) Does anyone know where I can get copies of Wincrypt.h and advapi32.lib (which I believe I'd need in order to compile against advapi32.dll)?

III) Can anyone offer any suggestions to get me started down this crazy path?

---

Added after 20 minutes:

Well, I found my own answer for B: Download the headers and libs section of the Windows SDK.

[high_flyer]

Not sure what your current question is, I mean, now that you have the libs and headers, what is the problem you are facing now?

[DanH]

Well, mainly I'm wondering about linking to M$ libs in Qt Creator -- whether the compiler and linker can handle it, or if M$ does some things to make it hard/impossible outside of VS. (I'm assuming I'll probably need extern"C" for the interfaces, but do I need anything else?)

Also, I'm wondering about the library-within-a-library situation -- IIRC there are some restrictions there, with Qt.

[squidge]

You will find it difficult to link to Visual C-style libraries from MinGW, but if you use VC it will be no problem.

The IDE (Visual Studio or Qt Creator) doesn't matter as thats just a glorified text editor.

[high_flyer]

Well, mainly I'm wondering about linking to M$ libs in Qt Creator -- whether the compiler and linker can handle it, or if M$ does some things to make it hard/impossible outside of VS.

Just to add to what squidge said:
Lib linking to a lib is not a problem, why should it be? the same rules apply.
You will need extern C if you have C code in your libs yes, but that is standard as well.
You will be well advised to use the same compiler for all libs, if for some libs you have only the binary and no source, try to find out with which compiler they where built, and build your new libs with that compiler.
MinGW and VS binaries are not compatible and wont inter-link (AFAIK).
You can configure Qt Creator to use cl.exe. (the MS compiler).
If you have the source to all the libs, then you can use any compiler, and just build everything from source with that compiler/linker.

[DanH]

If MinGW can't link to VS libraries, I'm wondering how a MinGW program can communicate with the OS??

(Bear in mind that the last time I interfaced with the M$ operating system was to port Tiny-C to the PC in the early 80s.)

[high_flyer]

The one thing has nothing to do with the other.
VS is using a lib file, or exports file to know the adderess of the exported symbols, when it needs to link while you build.
MinGW does not.
But it can be done ("mix linking"):
http://www.mingw.org/wiki/MSVC_and_MinGW_DLLs

[squidge]

If MinGW can't link to VS libraries, I'm wondering how a MinGW program can communicate with the OS??

Via stub libraries, but if your library is C++ then its going to be difficult. C is more standardised and easier to link to.

[Gokulnathvc]

Is it possible to include the dlls in the application itself instead of copying the dlls to the installed folders??? Please say me

[high_flyer]

Google about static linking, or search for it in the forum.

[DanH]

Well, I've managed to call a couple of Windows Crypto methods from Qt. It took a little song and dance to create the lib.a file, and I still have to create the .h file (and figuring out primitive type equvalence in C/C++ is a bear -- what's a long, what's a long long, what's a dword, etc). But that's just work, after the basic nut is cracked.

[high_flyer]

primitive type equvalence in C/C++ is a bear -- what's a long, what's a long long, what's a dword, etc)

Depends on the IDE you are using, either by hovering you will see the #define expansion, or right click and go to declaration.
All these types are nothing more than defines based on the basic C++ types - which by they way you can just define in your project if they are not defined.
Another option is, if your code is only meant for windows, you can just include "windows.h" and you are all sorted out with the windows types.

[DanH]

And, after doing that song and dance, I discovered (by accident) that many of the Windows interfaces, including header files and libs, are already included with MinGW. So the only tricky part is figuring out the type equivalences.