dcsimg

Using one extension DLL in another

WEBINAR:
On-Demand

Application Security Testing: An Integral Part of DevOps


If you create an extension DLL you can most conveniently export one or more of its classes using AFX_EXT_CLASS. However if you create a second extension DLL and try to use classes from the first you will run into a small problem.

The value of AFX_EXT_CLASS will cause your new DLL to try and export your dependent classes! You will get link errors such as below for the classes in the first DLL:

error LNK2001: unresolved external symbol ..........

What you need to do is temporarily re-define AFX_EXT_CLASS when you include the header files for the classes in the DLL you are importing classes from. The following example shows how to do this:

//change the definition of AFX_EXT... to make it import
#undef AFX_EXT_CLASS
#undef AFX_EXT_API
#undef AFX_EXT_DATA
#define AFX_EXT_CLASS AFX_CLASS_IMPORT
#define AFX_EXT_API AFX_API_IMPORT
#define AFX_EXT_DATA AFX_DATA_IMPORT

//Include headers for the dll / lib that we use classes from
#include "DLLOne.H"

//put the values back to make AFX_EXT_CLASS export again
#undef AFX_EXT_CLASS
#undef AFX_EXT_API
#undef AFX_EXT_DATA
#define AFX_EXT_CLASS AFX_CLASS_EXPORT
#define AFX_EXT_API AFX_API_EXPORT
#define AFX_EXT_DATA AFX_DATA_EXPORT

//Include headers for the classes we are creating in this DLL
#include "DLLTwo.H"

Posted: March, 8, 98



Comments

  • You must have javascript enabled in order to post comments.

Leave a Comment
  • Your email address will not be published. All fields are required.

Top White Papers and Webcasts

  • Discover the best practices from HPE’s IT Advisory Consulting Services for migrating and transforming applications in Hybrid IT by capitalizing on innovative platforms, modern application architectures, agile development tools and proven methodologies. There are a number of challenges our customers face when migrating and transforming applications for a Hybrid IT environment. This guide provide proven strategies and application approaches that can help them understand and reduce risks and complexity.

  • CEOs, CIOs, boards and shareholders are demanding digital transformation. They want their organizations to be more customer-focused, competitive and strategic to increase revenue. Data drives all of those aspects. A great first step in optimizing data use is moving data to the cloud. It can quickly show benefits. Here are six aspects of a cloud data management strategy that will help your organization more fully move, manage and use valuable data to successfully support digital transformation.

Most Popular Programming Stories

More for Developers

RSS Feeds

Thanks for your registration, follow us on our social networks to keep up-to-date
×
We have made updates to our Privacy Policy to reflect the implementation of the General Data Protection Regulation.