format PE GUI 4.0 DLL

include 'win32a.inc'

proc ShowMessage
  invoke MessageBoxA, 0, _msg, 0, MB_OK
  ret
endp

_msg db "This is the message in the DLL!", 0

data import

 library user32,'USER32.DLL'

 import user32,\
        MessageBoxA,'MessageBoxA'

end data

data export

 export 'DLL.DLL',\
        ShowMessage,'ShowMessage'

end data

section '.reloc' fixups data readable discardable    

format PE GUI 4.0

include 'win32a.inc'

 invoke ShowMessage
 invoke ExitProcess,0

data import

 library kernel32,'KERNEL32.DLL',\
         DLL,'DLL.DLL'

 import kernel32,\
        ExitProcess,'ExitProcess'

 import DLL,\
        ShowMessage,'ShowMessage'

end data
    

#include <windows.h>
#pragma comment(lib,"DLL.lib")

void WINAPI ShowMessage(void);

int main()
{
    ShowMessage();
    return 0;
}
    

C:\[...]\TEST.o:TEST.cpp|| undefined reference to `ShowMessage()@0'|
||=== Build finished: 1 errors, 0 warnings (0 minutes, 1 seconds) ===|

Start conversion.
Preparing for the conversion...
Convert DLL file into object files...
Warning 10: Cannot find corresponding export symbol for ShowMessage in the import libraries, we have to assume the export symbol follows __cdecl call convention.
Bind object files to static library files.
Conversion finished.

Try this:


DLL.asm

proc ShowMessage c


TEST.asm

cinvoke ShowMessage

TEST.cpp

void ShowMessage(void);

1. Make your DLL in FASM.
2. Make a header file with function type declaration
3. Make a static library project that dynamically imports from your DLL.
4. Link your EXE against the library in step 3 using the header file in step 2.

or cut it short to dynamic import within your EXE. After all, the .lib code ends up in your EXE anyway so you might as well just do the import in your EXE.

What I'm saying is. DLL2Lib is messing up your export name. If your function is __stdcall is should be __imp__<fn_Name>@paramCount*4 in the .lib file.

DLL2Lib says your function is __stdcall yet the name conforms to __cdecl.

By convention, anyone looking at _ShowMessage would think that this is a __cdecl.

So if you want to link with the lib, try changing your declaration to

extern void __cdecl _ShowMessage (or omit the __cdecl) or as whatever Dll2Lib tells you.
Remove the void parameter type as that will add an unnecessary parameter count. Also, make sure your actual function in the DLL is of the same calling convention.

OR

Simply link dynamically.

#pragma comment(lib,"DLL.lib")

void __cdecl ShowMessage();

int main(int argc, char **argv)
{

ShowMessage();

return 0;
}
    

For some reason the stupid Dll to Lib adds links to LIBC.lib.

Code:

#pragma comment(lib,"DLL.lib")

void __cdecl ShowMessage();

int main(int argc, char **argv)
{

ShowMessage();

return 0;
}
    

typedef wrote:

For some reason the stupid Dll to Lib adds links to LIBC.lib.

Code:

#pragma comment(lib,"DLL.lib")

void __cdecl ShowMessage();

int main(int argc, char **argv)
{

ShowMessage();

return 0;
}
    

This works for you? Then maybe my compiler is the guilty. It's GNU GCC Compiler. I'll try to compile with another.

format MS COFF

public ShowMessage as '_ShowMessage@0'
extrn '__imp__MessageBoxA@16' as MessageBoxA:dword

include 'win32a.inc' 

section '.code' code readable executable
        proc ShowMessage 
                invoke MessageBoxA, 0, msg, 0, MB_OK
                ret
        endp

section '.data' data readable writeable
        msg db 'This is the message in the DLL!', 0 
    

//Add .obj file to linker
//In VC++: Project Properties -> Configuration Properties -> Linker -> Input -> Additional Dependencies
//You can add library directory in Project Properties -> Configuration Properties -> VC++ Directories
//#pragma comment(lib, ".obj"); doesn't work
void __stdcall ShowMessage(void);

int main(void) {
        ShowMessage();
        return 0;
}
    

A$M wrote:

typedef wrote:

For some reason the stupid Dll to Lib adds links to LIBC.lib.

Code:

#pragma comment(lib,"DLL.lib")

void __cdecl ShowMessage();

int main(int argc, char **argv)
{

ShowMessage();

return 0;
}
    

This works for you? Then maybe my compiler is the guilty. It's GNU GCC Compiler. I'll try to compile with another.

I hope you are actually using a C compiler though I don't see why it would impede the linking process convention-wise.

And you need to have libc.lib as that stupid dll to lib requires it. DLL to Lib is the culprit and your log says it all. I rest my case.

#include <Windows.h>

typedef void (WINAPI *FUNC)(void);

int main(int argc, char **argv)
{
        HMODULE DLL;
        FUNC ShowMessage;
        DLL = LoadLibrary("DLL.dll");
        if (!DLL) { MessageBox(NULL, "DLL.dll is missing.", "ERROR", MB_OK + MB_ICONERROR); return -1; }
        ShowMessage = (FUNC)GetProcAddress(DLL, "ShowMessage");
        ShowMessage();
        return 0;
}