How to use multiple development languages

Question

I program in Delphi (D7 and D2006) on Windows XP (migrating in the near future to Windows 7). I need to use a mathematical library for some of the work I am doing and most of the math libraries (I am inclining towards Mathematica at present) I have looked at will produce compiled C code. Such code will provide specific functionality to my main programs.

I have a very basic question - given this development setup - how do I start utilising the compiled c code from Delphi? I really need baby steps to get me started on the process.

Answer 1

I've done quite a bit of this with my FE product OrcaFlex. You have two options to link to your C code from Delphi: static or dynamic. I link statically because it makes distribution and versioning much easier. But it's really quite a trick to get it to work statically and you have to rely on a number of undocumented aspects of Delphi.

I suspect that for your needs dynamic linking is best. Basically you need to compile and link your C code into a DLL. I recommend using the Borland C compiler to do this. You can use the free command line version BCC55 to do this. The advantage of using Borland C is that it makes the same assumptions about the 8087 floating point unit as Delphi does. If you build with MSVC then you will find that MS have elected not to raise floating point exceptions. Borland C does raise floating point exceptions. This is a bit of a corner case but it becomes relevant if you are trying to ship a product that you need to be robust.

You should know that the C code will, by default, use the C calling convention and I'd just stick with that. You bring it into Delphi by declaring the external routine as cdecl calling convention.

The other thing you need to take care on is defining a clear interface between the two modules. You need to make sure that exceptions don't cross the module boundary and that you don't pass any special types (e.g. Delphi strings) across the boundary. So for a string use a PChar (or even better PAnsiChar or PWideChar to be sure that it won't change meaning when you upgrade to Delphi 2009 and later).

Answer 2

I have been very happy with the SDL Library from Lohninger (http://www.lohninger.com/mathpack.html). It is written in Delphi and compiles right into your application, so there are no bundling or calling convention problems or floating point usage differences, as discussed by other responses in this thread.

Take a look at what he includes. If you're lucky, your needs will be met by his library and you'll be able to use it!