Delphi to C++ Builder Migration Checklist — Tools, Tips, and PitfallsMigrating a codebase from Delphi (Object Pascal) to C++ Builder can unlock benefits like access to modern C++ libraries, better integration with C/C++ ecosystems, and performance optimizations. But it’s also a non-trivial process: language differences, component libraries, memory management, and build systems all cause friction. This checklist provides a practical, step-by-step roadmap, recommended tools, common pitfalls, and concrete tips to make the migration smoother.
1. Assess the project and define scope
- Inventory code and assets:
- Identify Delphi source files (.pas, .dfm/.fmx, .dproj), resources, third-party components, and build scripts.
- Flag UI frameworks used (VCL vs FireMonkey).
- Determine migration goals:
- Full rewrite vs incremental porting vs interoperability (mixed-language project).
- Target C++ Builder version and compiler (RAD Studio version).
- Evaluate risk and timeline:
- Identify mission-critical modules and create a priority list.
- Estimate effort per module and plan a pilot project.
2. Choose a migration approach
- Full conversion:
- Translate all Delphi code to native C++ Builder C++ code. Best for long-term uniformity but most effort.
- Incremental porting:
- Convert modules gradually, use interop layers to call Pascal from C++ or vice versa.
- Interoperability (mixed-language):
- Keep stable Delphi units and expose interfaces usable by C++ Builder (DLLs, packages, COM).
3. Tools and utilities
- C++ Builder IDE (RAD Studio) — required to build and debug converted projects.
- Delphi-to-C++ conversion helpers:
- Built-in C++ Builder header generation for Delphi packages (creates C++ headers from Pascal units).
- Third-party converters and scripts (use cautiously; often require manual fixes).
- Version control (Git) — create a migration branch and tag milestones.
- Build automation — adopt or adapt existing CI to handle both Pascal and C++ builds.
- Static analyzers and linters for C++ (e.g., clang-tidy) to enforce code quality after conversion.
- Binary diff tools (beyond compare) to verify resource and form parity.
4. Project setup in C++ Builder
- Create a new C++ Builder project matching original project structure.
- Import forms:
- VCL .dfm files can be used by C++ Builder; ensure form streaming compatibility.
- For FireMonkey, check .fmx compatibility between Delphi and C++ Builder versions.
- Convert project options (compiler defines, search paths, packages).
- Recreate packages: Delphi packages may require rebuilding or wrapping as C++ packages.
5. Language and code translation checklist
- Basic syntax:
- Translate Pascal constructs to C++ equivalents: procedures/functions → functions/methods; records → structs/classes.
- Pay attention to case sensitivity (C++ is case-sensitive; Object Pascal is not).
- Data types:
- Map common types: Integer/LongInt → int32_t or appropriate C++ integral types; Cardinal → uint32_t.
- Strings: Delphi’s UnicodeString ↔ C++ Builder’s UnicodeString (VCL) or std::wstring/std::u16string depending on use.
- Enumerations: ensure exact integer sizing if binary compatibility is required.
- Memory management:
- Delphi’s automatic reference counting for certain types differs from C++ manual management. Use smart pointers (std::unique_ptr/std::shared_ptr) or C++ Builder RTL utilities where appropriate.
- Interfaces and COM:
- Delphi interfaces vs C++ abstract classes — ensure reference-counting semantics are preserved.
- Exception handling:
- Convert try..except/try..finally to try/catch and RAII patterns (std::lock_guard, destructors) for cleanup.
- Events and method pointers:
- Delphi method pointers (TNotifyEvent) map to C++ method pointers or std::function; C++ Builder provides compatibility types — prefer the latter when integrating with VCL.
- Properties:
- Pascal properties have no direct C++ language equivalent; implement via getter/setter methods or C++ Builder property extensions.
6. UI and component migration
- VCL:
- VCL is supported in C++ Builder; many components and .dfm forms are usable directly, but event handler signatures and form unit names will change.
- Relink event handlers after conversion; adjust __fastcall calling conventions if needed.
- FireMonkey:
- FMX compatibility is generally good but verify platform-specific behavior.
- Third-party components:
- Check availability of C++ Builder versions of components. If none exist, consider:
- Keeping the component as a Delphi package and using interop.
- Replacing with alternative components.
- Rewriting component functionality in C++.
- Check availability of C++ Builder versions of components. If none exist, consider:
- Resources and images:
- Ensure resource (.res) files and image assets are included and paths updated.
7. Build, link, and runtime checks
- Resolve symbol and linker issues:
- Name mangling and calling conventions can cause unresolved externals; use extern “C” for C-style exports or adjust linkage settings.
- Library compatibility:
- Rebuild any static libraries from source for the C++ toolchain; avoid mixing Delphi-compiled binaries unless explicitly supported.
- Runtime tests:
- Run unit tests, integration tests, and UI smoke tests after each converted module.
- Memory and performance profiling:
- Use profilers to detect regressions introduced during conversion.
8. Data storage and serialization
- Binary formats:
- If you need binary compatibility with existing files/databases, ensure data type sizes, packing, and endianness match.
- Reproduce Delphi record layouts with explicit packing directives (#pragma pack) and integer typedefs.
- Object streaming:
- VCL form streaming differences can break load/save — test form streaming especially when mixing Delphi and C++ Builder modules.
- Database access:
- Update database components (dbExpress, FireDAC, third-party) and connection strings; test query results for type mapping differences.
9. Testing strategy
- Create a test matrix:
- Unit tests for translated logic.
- GUI tests for forms and workflows.
- Regression tests for file formats and APIs.
- Automate tests in CI:
- Run builds and tests on merge to migration branches.
- Acceptance criteria:
- Define pass/fail conditions per module (e.g., performance within X%, binary compatibility, feature parity).
10. Common pitfalls and how to avoid them
- Assuming 1:1 language features — many constructs need redesign rather than direct translation.
- Ignoring calling conventions — leads to crashes; verify __fastcall, STDCALL, cdecl as needed.
- Overlooking Unicode/string behavior — test all string I/O and UI text.
- Third-party component gaps — inventory and plan replacements early.
- Memory leaks and ownership differences — adopt smart pointers and RAII patterns.
- Build configuration drift — keep compiler and linker settings consistent with original behavior where compatibility matters.
11. Practical tips
- Start with a non-critical pilot module to refine the process.
- Keep Delphi code compilable during migration to allow quick rollback.
- Maintain clear interface boundaries between converted and original modules to minimize integration friction.
- Use automated refactoring tools in the IDE for repetitive renames and signature updates.
- Document translation conventions (type mappings, naming rules, resource handling) so the team applies consistent patterns.
12. Post-migration checklist
- Full regression test pass completed.
- Performance and memory profiling acceptable.
- All third-party components either migrated, replaced, or wrapped.
- CI adjusted to build and test the new C++ project.
- Documentation updated (developer setup, build steps, runtimes).
- Retirement plan for old Delphi-only branches.
Quick reference: common Delphi → C++ type mappings
| Delphi | C++ Builder / C++ |
|---|---|
| Integer / LongInt | int32_t (or int) |
| Cardinal | uint32_t |
| SmallInt | int16_t |
| Byte | uint8_t |
| Boolean | bool |
| String / UnicodeString | UnicodeString (VCL) or std::wstring |
| Char | wchar_t (or char16_t depending on use) |
| TObject | TObject (C++ Builder RTL) or base C++ class |
| TList / TObjectList | TList equivalents or std::vector/std::list |
Migrating from Delphi to C++ Builder is achievable with careful planning, a strong testing regimen, and attention to language and runtime differences. Follow this checklist, run a pilot, and iterate — the hardest part is organizational and architectural, not just syntax.
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