Background: I have a DLL I created that includes 2 c files. These c files reference a third c file which defines a user defined type (we’ll call it class_pointer), which is a pointer of type class.
E.g.
typedef class pointer_class *class_pointer;
then defines the class:
typedef class pointer_class {..}
pointer_class has various variables and functions associated with it that the original 2 c files make use of through class_pointer.
I am using this DLL in an ASP.NET C# web application. I am using PInvoke to import the functions into the dll. However, when I go to call on these functions that involve the class_pointer, the website running on IIS hangs. This does not happen in the VS debugger. If I comment out said class_pointers, everything runs smoothly — I have access to the DLL and everything.
I have tried changing the permissions on all the DLLs included in my bin directory (just to be safe) for NETWORK SERVICE to have read/execute permissions. The dll will work without the class_pointers, so I don’t think it is an issue of permissions. Does anyone have any advice on what might be causing IIS to hang when these class_pointers are involved?
I finally was able to figure this out with the help of Microsoft’s debugging tools.
The class_pointers were written by another developer that has since left the place I work. In the pointer_class, there was a function to get the current application path. When running on the web, this was set to the inetsrv directory in SYSWOW64 (The machine I was running on was a 64bit machine). To solve the issue, we set the application path to the website when we are running the web, rather than where the .exe application was running from (SYSWOW64/inetsrv).
Because the application path was wrong, the native dll was unable to load some files in and was putting up popup warning messages. These pop up messages were waiting for a user response and since we couldn’t get one on the web, the application hanged!
Hope this helps someone else out there!