Thread: really, really basic DLL use

Heya, I'm a mostly UNIX C++ programmer who is trying to transition into Windows programming, and I would like to know how to create and call a DLL. I am used to the "compile as a shared library, declare as extern, and pass the library's name to the linker through the command line" paradigm. I have examined numerous Windows tutorials that don't address the starting points. My question (and please point me to a tutorial that covers this if you know of one):

1. What special commands do I put into a program if I want to compile it into a DLL?
2. What special commands to I put into the program that calls the function in the DLL?
3. What kind of compiler/linker options do I need to use, specifically for Borland command-line tools?

If it would make it easier, lets use an example:

Let's say I want to compile the following program into a DLL:

Code:

#include <iostream>

void hello() {
    std::cout << "Hi there!" << endl;
}

Normally I would use the following syntax in the calling program:

Code:

extern void hello();
int main() {
    hello();
}

Then I would compile the first code with the -G command in the CC compiler to create a dynamically shared library, and compile the second with the -l command which tells the linker to look in the hello library for the hello function. So, if you please, take these code snippets and add to them the necessary verbiage for DLLs.

Originally posted by kuphryn
Here is the code you need infront of the source code to export a DLL.

Code:

extern "C" __declspec(dllexport) void hello()
{
    std::cout << "Hi there!" << endl;
}

Kuphryn

That may work in Borland...but I'm not sure......

If Borland doesnt support __declspec(dllexport) then you have to use a .DEF file in the dll project to tell the linker what to export.....bets bet is to look at the documentation for your compiler & linker...

BTW, Kuph.....managed to do a dll like that in MASM yet?

Okay, please forgive my density:

I have the following:

Code:

#include <iostream>

extern "C" __declspec(dllexport) void hello() {
    std::cout << "Hi there!" << std::endl;
}

saved as hello.cpp. I compiled this with:

bcc32 -WD hello.cpp

which generated hello.dll, hello.obj, and hello.tds. I then have:

Code:

extern "C" __declspec(dllexport) void hello();

int main() {
    hello();
}

which is saved as test.cpp. I try to compile with
bcc32 -L. test.cpp
with the -L. flag set to add the current directory to the linker's search path. I receive the following linker error:

Error: Unresolved external '_hello' referenced from E:\CODE\CPP\WINTEST\TEST.OBJ

Obviously it can't find the right path, which means that I have left out a critical step somewhere. I have looked all through the linker options and seen nothing that says to me "use this option to specifically link to this DLL". I realize that this is simple stuff for y'all, but please bear with me.

When you create the dll, there should be a .lib file created...this need to be used with your main program

Kuph:

To whet your appitite;

KuphDll.asm

Code:

.386
.model flat,stdcall
option casemap:none
include \masm32\include\windows.inc
include \masm32\include\user32.inc
includelib \masm32\lib\user32.lib          
include \masm32\include\kernel32.inc
includelib \masm32\lib\kernel32.lib

hello proto 
DllEntry proto hInstDLL: HINSTANCE, reason: DWORD, reserved1: DWORD



.DATA 

MyStr BYTE "Hi Kuphryn!",'0'
hCon HANDLE NULL
dwDummy DWORD NULL

;#####################################################
;#####################################################


; STARTUP

.CODE              

DllEntry proc hInstDLL: HINSTANCE, reason: DWORD, reserved1: DWORD
       mov eax,TRUE
       ret
DllEntry Endp


hello proc 
	invoke GetStdHandle,STD_OUTPUT_HANDLE
	mov hCon,eax
	invoke WriteConsole,hCon,ADDR MyStr,11,ADDR dwDummy,NULL
	ret
hello endp

end DllEntry

KuphDll.def

Code:

LIBRARY KuphDll
EXPORTS hello

Build.bat

Code:

'Change these paths if needed
C:\masm32\BIN\ML.EXE /c /coff /Cp KuphDll.asm
C:\masm32\BIN\LINK.EXE /DLL /DEF:KuphDll.def /SUBSYSTEM:WINDOWS /LIBPATH:c:\masm32\lib KuphDll
PAUSE

Now that should produce a dll and a lib....

Now...Kuph.Cpp

Code:

extern "C" void __stdcall hello(void);

int main(void){

	hello();
	return 0;
}

Make sure you include the lib in the cpp project and have the dll in the same dir as the exe.........

Gotta love MASM......all the cool, but stripped to the flesh!!!!!