F.9 Building DLLs with GNAT

• Limitations When Using Ada DLLs from Ada
• Exporting Ada Entities
• Ada DLLs and Elaboration
• Ada DLLs and Finalization
• Creating a Spec for Ada DLLs
• Creating the Definition File
• Using gnatdll

This section explains how to build DLLs containing Ada code. These DLLs will be referred to as Ada DLLs in the remainder of this section.

The steps required to build an Ada DLL that is to be used by Ada as well as non-Ada applications are as follows:

1. You need to mark each Ada entity exported by the DLL with a C or Stdcall calling convention to avoid any Ada name mangling for the entities exported by the DLL (see Exporting Ada Entities). You can skip this step if you plan to use the Ada DLL only from Ada applications.
2. Your Ada code must export an initialization routine which calls the routine adainit generated by gnatbind to perform the elaboration of the Ada code in the DLL (see Ada DLLs and Elaboration). The initialization routine exported by the Ada DLL must be invoked by the clients of the DLL to initialize the DLL.
3. When useful, the DLL should also export a finalization routine which calls routine adafinal generated by gnatbind to perform the finalization of the Ada code in the DLL (see Ada DLLs and Finalization). The finalization routine exported by the Ada DLL must be invoked by the clients of the DLL when the DLL services are no further needed.
4. You must provide a spec for the services exported by the Ada DLL in each of the programming languages to which you plan to make the DLL available.
5. You must provide a definition file listing the exported entities (see The Definition File).
6. Finally you must use gnatdll to produce the DLL and the import library (see Using gnatdll).