xpact

xpact is an Eiffel XML parser project inspired by Finnian Reilly's Eiffel.org proposal, "Finding a billion-user project for Eiffel: How DbC catches the security flaws that Rust misses."

Tagline: XML parsing, by contract.

The project goal is to use libexpat as the public reference point while keeping the parser semantics owned by Eiffel. The C code in native/ is an ABI bridge: it exports libexpat-shaped symbols and delegates parsing to Eiffel classes. It is not intended to become a second C parser.

Current Status

This checkpoint is a Windows-only Phase 1 preview, not a final drop-in replacement for libexpat.

Implemented and verified now:

• Eiffel targets explicitly compile with void safety enabled (support="all" use="all"), using the safe Base precompile.
• Contract-backed temporary garbage-collection suspension for critical parse sections.
• XML 1.0 tokenization and entity handling in Eiffel.
• Capability-based external entity resolver policy: xpact does not open files, URLs, or sockets by itself.
• A libexpat 2.8.1 public API header surface in include/xpact.h.
• A Windows x64 Eiffel-backed xpact.dll build path.
• C ABI smoke tests for public callers and for the private Eiffel bridge.
• A native C benchmark path against the Windows Eiffel-backed DLL.
• An upstream libexpat test-suite adapter with explicit green/red parity rows.
• Published benchmark, performance-analysis, and parity documentation.

The upstream Expat 2.8.1 manifest currently has 399 START_TEST(...) entries. The expected-failure list expands to 88 rows:

• 86 allocator-injection tests are intentionally out of the current Eiffel release scope because they exercise libexpat's manual C allocation hook contract.
• 2 non-allocator rows remain red: exact Expat large-buffer scan-count and reparse-buffer heuristic behavior.

What Is Left

Before calling xpact a credible drop-in replacement, the project still needs:

• elimination or explicit product decision for the two non-allocator reparse-buffer heuristic gaps;
• a stronger native-suite gate that reports actual unexpected failures by upstream test name, not only the current expected-failure manifest expansion;
• replacement testing in at least one public application that normally builds against libexpat;
• Linux/WSL packaging for an Eiffel-backed libxpact.so;
• broader consumer ABI coverage across compilers and build systems;
• a release decision on whether allocator-injection semantics are intentionally unsupported or emulated at the C ABI boundary.

Reading Order

Start here, then read:

1. docs/article-reading-guide.md for how the repository maps to the original Eiffel.org article and the Design by Contract argument.
2. docs/phase-1.md for the full Windows Phase 1 scope.
3. docs/design-overview.md and docs/bon/ for the design map and BON views.
4. docs/libexpat-api-compatibility.md for the public C API surface.
5. docs/libexpat-parity.md and adapters/libexpat/parity.tsv for green/red upstream test-suite status.
6. docs/benchmarks.md for same-machine benchmark results.
7. docs/performance-analysis.md for the current xpact-vs-libexpat performance gap analysis and next optimization priorities.
8. docs/drop-in-verification.md for the Jenkins and public-application replacement plan.

Build And Verify

Compile and run the Eiffel regression tests:

ec -batch -config tests\xpact_tests.ecf -target xpact_tests
.\EIFGENs\xpact_tests\W_code\xpact_tests.exe

Build the Windows Eiffel-backed native DLL:

.\scripts\build_native_eiffel.ps1

Run native ABI/link smoke tests:

.\scripts\run_native_abi_tests.ps1 -Target Windows

Refresh the upstream Expat manifest and parity expansion:

.\scripts\run_libexpat_adapter.ps1 `
  -Mode Manifest `
  -ExpatSourceDir .\build\libexpat-R_2_8_1\libexpat-R_2_8_1\expat `
  -OutputDir .\build\libexpat-adapter-current `
  -XpactLibrary .\build\native-eiffel\xpact.lib `
  -SkipNativeBuild

Package the Windows x64 preview release:

.\scripts\package_windows_release.ps1