Как вызывать функцию 16-битной DLL из 32-битного приложения?

Надо использовать Thunks.

Кусок работающего только под Windows 95 кода -

const
   Gfsr_SystemResources = 0;
   Gfsr_GdiResources = 1;
   Gfsr_UserResources = 2;
 var
   hInst16: THandle;
   GFSR: Pointer;
 { Undocumented Kernel32 calls. }
 function LoadLibrary16(LibraryName: PChar): THandle; stdcall; external kernel32 index 35;
 procedure FreeLibrary16(HInstance: THandle); stdcall; external kernel32 index 36;
 function GetProcAddress16(Hinstance: THandle; ProcName: PChar): Pointer; stdcall; external kernel32 index 37;
 procedure QT_Thunk; cdecl; external kernel32 name 'QT_Thunk';
 { QT_Thunk needs a stack frame. }
 {$StackFrames On}
 { Thunking call to 16-bit USER.EXE. The ThunkTrash argument
 allocates space on the stack for QT_Thunk. }
 function NewGetFreeSystemResources(SysResource: Word): Word;
 var
   ThunkTrash: array[0..$20] of Word;
 begin
   { Prevent the optimizer from getting rid of ThunkTrash. }
   ThunkTrash[0] := hInst16;
   hInst16 := LoadLibrary16('user.exe');
   if hInst16 < 32 then
     raise Exception.Create('Cannot load USER.EXE!');
   { Decrement the usage count. This doesn't really free the
     library, since USER.EXE is always loaded. }
   FreeLibrary16(hInst16);
   { Get the function pointer for the 16-bit function in USER.EXE. }
   GFSR := GetProcAddress16(hInst16, 'GetFreeSystemResources');
   if GFSR = nil then
     raise Exception.Create('Cannot get address of GetFreeSystemResources!');
   { Thunk down to USER.EXE. }
   asm
     push SysResource { push arguments }
     mov edx, GFSR { load 16-bit procedure pointer }
     call QT_Thunk { call thunk }
     mov Result, ax { save the result }
   end;
 end;

Автор: Quality freeware from Sight&Sound, Slovenia, http://www.sight-sound.si

Автор: Андрей Гусев (Andrey Gusev)

Взято из Akzhan's Delphi-related VCL&WinAPI Tips'n'Tricks

---

Посылаю код для определения системных ресурсов (как в "Индикаторе ресурсов"). Использовалась статья "Calling 16-bit code from 32-bit in Windows 95".

{ GetFeeSystemResources routine for 32-bit Delphi.
 
Works only under Windows 9x }
 
 
unit SysRes32;
 
interface
 
const
//Constants whitch specifies the type of resource to be checked
 
 
GFSR_SYSTEMRESOURCES = $0000;
GFSR_GDIRESOURCES    = $0001;
GFSR_USERRESOURCES   = $0002;
 
// 32-bit function exported from this unit
 
function GetFeeSystemResources(SysResource: Word):Word;
 
implementation
 
uses
 
SysUtils, Windows;
 
type
 
//Procedural variable for testing for a nil
 
TGetFSR = function(ResType: Word): Word; stdcall;
 
//Declare our class exeptions
 
EThunkError = class(Exception);
EFOpenError = class(Exception);
 
var
 
User16Handle : THandle = 0;
GetFSR       : TGetFSR = nil;
 
//Prototypes for some undocumented API
 
 
function LoadLibrary16(LibFileName: PAnsiChar): THandle; stdcall;
external kernel32 index 35;
 
 
function FreeLibrary16(LibModule: THandle): THandle; stdcall;
external kernel32 index 36;
 
 
function GetProcAddress16(Module: THandle; ProcName: LPCSTR): TFarProc;stdcall;
external kernel32 index 37;
 
 
procedure QT_Thunk; cdecl;
external 'kernel32.dll' name 'QT_Thunk';
 
 
{$StackFrames On}
 
function GetFeeSystemResources(SysResource: Word):Word;
var
 
EatStackSpace: String[$3C];
begin
// Ensure buffer isn't optimised away
 
EatStackSpace := '';
@GetFSR:=GetProcAddress16(User16Handle,'GETFREESYSTEMRESOURCES');
if  Assigned(GetFSR) then  //Test result for nil
asm
//Manually push onto the stack type of resource to be checked first
 
push  SysResource
//Load routine address into EDX
 
mov   edx, [GetFSR]
//Call routine
 
call  QT_Thunk
//Assign result to the function
 
mov   @Result, ax
end
else raise EFOpenError.Create('GetProcAddress16 failed!');
end;
 
initialization
 
//Check Platform for Windows 9x
if Win32Platform <> VER_PLATFORM_WIN32_WINDOWS then
 
raise EThunkError.Create('Flat thunks only supported under Windows 9x');
 
//Load 16-bit DLL (USER.EXE)
User16Handle:= LoadLibrary16(PChar('User.exe'));
 
if User16Handle < 32 then
raise EFOpenError.Create('LoadLibrary16 failed!');
 
finalization
 
//Release 16-bit DLL when done
if User16Handle <> 0 then
 
FreeLibrary16(User16Handle);
 
end.

Взято с https://delphiworld.narod.ru