Using libraries compiled with Cygwin

[JovianGhost]

I'm trying to integrate a library into my Qt project; specifically, this one: http://trac.osgeo.org/proj/

I would like to link statically, so I downloaded the zipped source and extracted. I then compiled the library in a Cygwin environment (I'm on a Windows platform) and consequently got my static library objects.

Now I tried linking to them, but something odd happened.

First when I ran it from Qt Creator, the program terminated immediately with an error code. So I tried running the executable from the debug directory, and it complained about missing Cygwin DLLs, specifically cygproj-0.dll and cygwin1.dll. Why do I need these libraries in my Qt project, when I'm not explicitly linking to them? Is it because the library I AM linking to was compiled in a Cygwin environment? Is there a way around this?

So I copied over the necessary DLLs, but now when I run my executable, I can see that it appears in Task Manager, but just appears to be eating up CPU cycles (takes up 50% on my dual-core system.)
I know there's nothing wrong with the libraries themselves, because if I write a very simple, minimalistic program (no using Qt, but just a simple C-program with a mainline) and link to the library, it runs just fine.

Any idea what's going on?

[squidge]

Yes, an application written using Cygwin requires the Cygwin DLLs. If you don't like this, use MinGW, and then you only need the MinGW DLLs in certain cases (if you use exceptions, I believe).

[JovianGhost]

Alright, that explains that.

But I still don't understand why my Qt app freezes when linked to this library. If I try to create a very minimalistic Qt app and link, it doesn't work.

Does Qt not play nice with external libraries?

[squidge]

Maybe you don't have the calling convention correct ? The wrong calling type will trash the stack and crash your application.

[JovianGhost]

Calling convention is definitely correct. Used the same thing for both test programs. The one compiled without Qt worked, the one compiled with Qt did not.

[walker_wwy]

I have the same issue by linking loundmouth library by Cygwin. To link the library without Qt is fine, but if linked with Qt, the program will eat 100% cpu

[Se7en]

Sorry if this is just totally wrong (I'm still a n00b) but would how you compiled the Cygwin stuff have anything to do with the problem?

http://www.mingw.org/wiki/FAQ
Scroll down to the section: "How do I use MinGW with Cygwin"