Cannot load DLL.

[cmp1104]

I am using Qt 4.7 on a Windows 7, 64-bit machine. I am trying to load a third party DLL. In their source file they call LoadLibraryA(functionName) to load the library at run time. The code checks for a handle returned when the DLL is loaded.

This is my problem: Every time I run my code it gets to the point of loading the library but the returned handle value is NULL. This causes the program to crash (Segmentation fault). In my application output window I get "(Internal error: pc 0x0 in read in psymtab, but not in symtab.)".

The twists: Originally another programmer integrated the third party code into the application and the application runs just fine on his machine. I am using his code exactly and I get the crash. I tried the application on a 32-bit laptop. Originally it did not work. However when I uninstalled Qt 4.7 and reinstalled it, the application works. (This may be a red herring....)

Debugs I have tried: 1) I have tried using Dependency Walker. The results I get when I run DW on my application exe are the same ones he gets. 2) I have uninstalled and re-installed Qt on my machine 3) I have verified that the DLL is in the same directory as the executable

Any thoughts?

Thanks.

[d_stranz]

Is your Qt app compiled as a 64-bit app? Is the third-party DLL a 64-bit DLL? On Windoze 7, all executable parts (exe, dll, etc.) must be all 64-bit or all 32-bit. You can't mix and match 64-bit and 32-bit like you could with 32-bit and 16-bit code on Windows XP.

If the 3rd-party DLL is 32-bit, try recompiling your app (and Qt) in 32-bit mode (or get someone else to do it with a 32-bit compiler and Qt) and see if that makes a difference. A 32-bit app with all dependencies also 32-bit will run just fine on Win 7.