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Using
C object files with Delphi XE2 - written by Jose Pascoa
(Revisions: 8th October 2012 - Using variables from Delphi in
Visual Studio and from Visual Studio in Delphi)
After I wrote, a couple of day ago, the article on the theme of
using Assembly
Language with Delphi, one of the gurus at the
Embarcadero's Forums told me that I was wrong because Delphi XE2
does accept COFF formatted object files not only when compiling
for 64-bit but also for 32-bit. I started Visual Studio 2010 to
confirm and you know? He was damn right!
There are literally, millions of lines of 'C' code waiting to be
compiled and linked with Delphi in order to receive a nice GUI.
I know that Embarcadero has C++ Builder, but for pure (no
GUI) C or C++ development it stays behind Visual Studio in every
respect.
The question now is: "Is it easy to link with Delphi
XE2 code compiled with Visual Studio?"
The answer is: "It is not difficult, just pay attention to a few
details. It is even easier for 64-bit code"
To
show how it is done, let's open VS 2010, select New Project in
the File Menu and go to the Visual C++ section. You can select
the Empty Project on the General node but is preferable to
select either Win32 Console Application or Win32 Project
on the Win32 Project node because allows you to test the whole
in VS. After doing this, add a C++ File and a Header File from
the Project menu. These 2 files are the ones where we are going
to put the code that will compile and link with Delphi. In
Solution Explorer right-click the new C++ file you just added,
select Properties and in the sub-node Advanced of the C/C++ node
select Compile as C Code (/TC) and in the Precompiled Headers
sub-node select Not Using Precompiled Headers. Now, in the
Project Properties, General node select Use Unicode Character
Set. Disable all settings of the project that deal with
exception handling to avoid complications (i.e, Enable C++
Exceptions="No" and Buffer Security Check = "No"). Finally, set
Whole Program Optimization to "No" in the Optimization sub-node.
You are set and can start coding away your C functions. When
done, right-click on the source file and select Compile. Do
compilations for 32-bit and 64-bit then copy the .obj files to
the folder where you have the Delphi XE2 project.
The Delphi linker has neither information about the parameters
of the functions you defined in VS2010 nor information
about all the externals that need to be resolved at link time by
the Delphi Linker. So, you need to declare all that in a Delphi
unit.
To
link with 32-bit Delphi programs, the golden rules are: 1) All the
function declarations will be proceeded by an underscore and the
calling convention should be cdecl (all right, this is the
default). 2) All the externals should have the cdecl calling
spec, if it is a call to a Windows API you must use in VS an
intermediate function with cdecl calling spec (see our demo
program to see how we solved the call to the MessageBoxW API) 3)
Genuine externals with the cdecl calling spec are probably
exports from msvcrt.dll and you can use this dll from your
Delphi program without need to figure out replacement functions
(see our demo program to see how).
To
link VS object files with 64-bit Delphi XE2 programs it easier
because: 1) There is only one calling convention, fastcall. 2)
Function names are not underscored. 3) Externals to the Windows
API are directly resolved without our action. 4) Using
msvcrt.dll functions is just a question of declaring them in
Delphi (see our demo program to see how).
All right, that's all about it. If you are not experienced with
'C', with Delphi, or with both~, things are not as easy as I put
them and you will have to work hard.
I
include complete source code (Delphi XE2 and VS 2010) for a demo
of what I have been writing about. A final note, in VS stdafx.h
file there is a #define DEBUGGING, You enable it to test the
routines in VS, you disable it when you compile just the
CtoDelphi.cpp file.
Download the VS2010 and Delphi
XE2
32-bit/64-bit demo program source code Now!
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