Avoid copying 3rd-party DLL into debug folder

Question

I have a C++ application that is built in Visual Studio (2008) and links to a Boost DLL. When debugging, it seems like I need to copy the Boost DLL into the debug folder so the exe I am running in the IDE can link to it. I could use a post-build step to copy the DLL, but I was wondering if there is a setting in Visual Studio that can give it an additional search path for DLLs while debugging?

Answer 1

There is a slight mis perception here. Visual Studio itself does not directly control the loading of DLL's into an application while you are debugging. The loading of DLL's is directly controlled by the operating system. The operating system searches a set of interesting directories for DLL's when a load is requested.

The main way in which VS influences the DLL's loaded is by virtue of copying them to the build output directory. This is typically the directory in which the application is run and hence is one of the paths the OS will search for necessary DLL's.

What directories the OS searches is controlled by a few items. The easiest of which to alter is the environment variable (LIBPATH I believe). In Debug mode you could alter this environment variable to point to your other directory and have the DLL load from there.

There is nothing you can directly set in Visual Studio though.

Answer 2

There are not of lot of options on Windows for DLLs that are implicitly linked to the EXE. Short from storing the DLL in the same folder as the EXE, you can store it in a directory that's listed on the PATH environment variable. Only c:\windows\system32 is guaranteed to be listed, you can't reasonably use that folder. An installer that changes the system environment would work, still not reasonable.

The only real option is to store the DLL in the WinSxS side-by-side cache. You'll need to write a manifest so that Windows can find the DLL. And you'll need to write an installer to put the DLL in WinSxS. Given the quality of the documentation, you'll need to really, really want to do that.

If this is only a consideration for debugging then perhaps it really isn't such a big deal to change the PATH on your dev machine. Use Control Panel, System applet.