Tutorial: Using Dynamic Libraries in C++Builder Applications (2025)

Contents

• • 1.1 The Dynamic-Link Library
    • 1.1.1 BaseStack.h
    • 1.1.2 StackOfInt.h
    • 1.1.3 StackOfInt.cpp
    • 1.1.4 StackExport.cpp
  • 1.2 The Firemonkey Application
    • 1.2.1 TestUnit.h
    • 1.2.2 TestUnit.cpp
• 2 Uses
• 3 See Also

// Base Virtual class for Stack.// Declared to be used both in StackLibrary.dll and TestStackLibrary.exe projectsclass BaseStack {public: virtual bool IsEmpty() = 0; virtual int Top() = 0; virtual int Pop() = 0; virtual void Push(int value) = 0;};

#include "BaseStack.h"// BaseStack implementation// Here the methods from BaseStack are implementedclass Stack : public BaseStack {private: // items holds the integers from the stack int* items; // represents the number of integers that are in the stack int count;public: // Stack constructor Stack(); // Stack destructor ~Stack(); // Checks whether the stack is empty bool IsEmpty(); // Returns the top of the stack int Top(); // Returns the top of the stack and removes the element from the stack int Pop(); // Inserts <code>value</code> into the stack void Push(int value);};

#include "StackOfInt.h"#define MAX_SIZE 30#define INDEX_OUT_OF_BOUNDS_EXCEPTION 1#define EMPTY_STACK 2// Stack constructorStack::Stack() { count = 0; items = new int[MAX_SIZE];}// Stack destructorStack::~Stack() { delete[]items;}// Returns the top of the stackint Stack::Top() { if (count > 0) { return items[count - 1]; } else { throw EMPTY_STACK; }}// Returns the top of the stack and removes the element from the stackint Stack::Pop() { if (count > 0) { return items[--count]; } else { throw EMPTY_STACK; }}// Checks whether the stack is emptybool Stack::IsEmpty() { if (count == 0) { return true; } else { return false; }}// Inserts <code>value</code> into the stackvoid Stack::Push(int value) { if (count < MAX_SIZE) { items[count++] = value; } else { throw INDEX_OUT_OF_BOUNDS_EXCEPTION; }}

// If your DLL exports any functions that pass String objects (or structs/// classes containing nested Strings) as parameter or function results,// you will need to add the library MEMMGR.LIB to both the DLL project and// any other projects that use the DLL. You will also need to use MEMMGR.LIB// if any other projects which use the DLL will be performing new or delete// operations on any non-TObject-derived classes which are exported from the// DLL. Adding MEMMGR.LIB to your project will change the DLL and its calling// EXE's to use the BORLNDMM.DLL as their memory manager. In these cases,// the file BORLNDMM.DLL should be deployed along with your DLL.//// To avoid using BORLNDMM.DLL, pass string information using "char *" or// ShortString parameters.//// If your DLL uses the dynamic version of the RTL, you do not need to// explicitly add MEMMGR.LIB as this will be done implicitly for you#pragma hdrstop#pragma argsused#include "StackOfInt.h"// This is the syntax for exporting methods from DLLs://// extern "C" __declspec(dllexport) void* __stdcall GetClassInstance();//// This method returns an instance of Stack:extern "C" __declspec(dllexport) void* __stdcall GetClassInstance() { return static_cast<void*>(new Stack);}extern "C" int _libmain(unsigned long reason) { return 1;}

//---------------------------------------------------------------------------#ifndef TestUnitH#define TestUnitH//---------------------------------------------------------------------------#include <System.Classes.hpp>#include <FMX.Controls.hpp>#include <FMX.Edit.hpp>#include <FMX.StdCtrls.hpp>#include <FMX.Types.hpp>#include <FMX.Forms.hpp>//---------------------------------------------------------------------------#include "BaseStack.h"//---------------------------------------------------------------------------class TForm1 : public TForm{__published: // IDE-managed Components TButton *PushButton; TButton *PopButton; TButton *TopButton; TButton *IsEmptyButton; TButton *LoadButton; TEdit *Edit1; void __fastcall PushButtonClick(TObject *Sender); void __fastcall PopButtonClick(TObject *Sender); void __fastcall TopButtonClick(TObject *Sender); void __fastcall IsEmptyButtonClick(TObject *Sender); void __fastcall LoadButtonClick(TObject *Sender);private: // User declarations BaseStack* stack; void __fastcall EnableButtons();public: // User declarations __fastcall TForm1(TComponent* Owner);};//---------------------------------------------------------------------------extern PACKAGE TForm1 *Form1;//---------------------------------------------------------------------------#endif

// ---------------------------------------------------------------------------#include <fmx.h>#pragma hdrstop#include "TestUnit.h"#include "StackOfInt.h"// ---------------------------------------------------------------------------#pragma package(smart_init)#pragma resource "*.fmx"TForm1 *Form1;// Holds the name of the dynamic-link library.const wchar_t* library = L"StackLibrary.dll";// type definition for pointer to functions that return (void*)typedef void* (*VoidReturnFunc)();// syntax that declares an imported functionextern "C" __declspec(dllimport) void* __stdcall GetClassInstance();// ---------------------------------------------------------------------------__fastcall TForm1::TForm1(TComponent* Owner) : TForm(Owner) {}// ---------------------------------------------------------------------------// Method used to enable the buttons when the library is loadedvoid __fastcall TForm1::EnableButtons() { PushButton->Enabled = true; PopButton->Enabled = true; IsEmptyButton->Enabled = true; TopButton->Enabled = true;}// ---------------------------------------------------------------------------// OnClick event handler for LoadButtonvoid __fastcall TForm1::LoadButtonClick(TObject *Sender) { // Dynamically loads the library HINSTANCE load = LoadLibrary(library); if (load) { ShowMessage("Library loaded!"); EnableButtons(); VoidReturnFunc myFunc; // GetProcAddress returns a pointer to the loaded method myFunc = (VoidReturnFunc)GetProcAddress(load, "GetClassInstance"); // Invoke GetClassInstance method stack = (BaseStack*) myFunc(); // Note: // The BaseStack methods are pure virtual methods, but myFunc() returns an instance of the Stack class. // Wherever we call stack->methodName() later, we are actually calling Stack::methodName(), not // BaseStack::methodName(). } else { ShowMessage("Library not loaded!"); }}// ---------------------------------------------------------------------------// OnCLick event handler for PushButtonvoid __fastcall TForm1::PushButtonClick(TObject *Sender) { if (stack) { try { int value = StrToInt(Edit1->Text); stack->Push(value); Edit1->Text = ""; } catch (int) { ShowMessage("Please insert an integer into the editbox!"); } }}// ---------------------------------------------------------------------------// OnClick event handler for IsEmptyButtonvoid __fastcall TForm1::IsEmptyButtonClick(TObject *Sender) { if (stack) { if (stack->IsEmpty()) { ShowMessage("The stack is empty!"); } else { ShowMessage("The stack is not empty!"); } }}// ---------------------------------------------------------------------------// OnClick event handler for PopButtonvoid __fastcall TForm1::PopButtonClick(TObject *Sender) { if (stack) { try { int value = stack->Pop(); ShowMessage("Popped " + IntToStr(value)); } catch (int Exception) { ShowMessage("Exception " + IntToStr(Exception)); } }}// ---------------------------------------------------------------------------// OnClick event handler for TopButtonvoid __fastcall TForm1::TopButtonClick(TObject *Sender) { if (stack) { try { int value = stack->Top(); ShowMessage("The top of the stack is " + IntToStr(value)); } catch (int Exception) { ShowMessage("Exception " + IntToStr(Exception)); } }}// ---------------------------------------------------------------------------