reactos/reactos
Oct 2024 – Sep 2025
12 Months active
Languages Used
CC++CMakeAssemblycmakePythonXMLinf
Technical Skills
API DevelopmentBuild SystemBuild System ConfigurationC ProgrammingC Runtime Library DevelopmentC++
Timo Kreuzer
PROFILE
Timo Kreuzer
Timo Kreuzer contributed to the reactos/reactos repository by developing and stabilizing core runtime libraries, kernel subsystems, and test infrastructure. He engineered features such as dynamic API test harnesses, locale and internationalization support, and robust floating-point and exception handling, using C, C++, and Assembly. His work included implementing Windows-compatible APIs, enhancing build system reliability with CMake, and improving cross-platform compatibility. Timo addressed kernel stability by refining memory management and resource handling, while expanding automated test coverage to reduce regressions. The depth of his engineering is reflected in careful refactoring, dynamic linking, and low-level system programming that improved maintainability and reliability.
Overall Statistics
Feature vs Bugs
59%Features
Repository Contributions
287Total
Bugs
71
Commits
287
Features
102
Lines of code
44,847
Activity Months12
Your Network
96 people
Work History
September 2025
7 Commits • 1 Features
Sep 1, 2025September 2025 monthly summary for reactos/reactos: Achievements focused on strengthening test reliability and kernel stability. Key feature delivered: the CRT API tests now dynamically load functions from ntdll, crtdll, and user32, consolidating refactors to cover _sn(w)printf, _vscprintf, _vsnprintf, _vsnwprintf, wctomb, and sprintf with improved robustness and accuracy. Major bug fixes include: preventing crashes from ObInsertObject failure by avoiding double dereference and proper resource handling; closing TokenHandle on SepOpenThreadToken failure to prevent leaks; correcting NtCreateEvent prototype in the NtCreateEvent tests to align with the correct parameter type. These changes reduce flaky tests and runtime risk, contributing to more reliable builds and kernel/user-mode interoperation. Technologies and skills demonstrated include C-level test harness improvements, dynamic symbol loading, Windows NT kernel concepts, and careful resource/handle management.
7 Commits • 1 Features
Sep 1, 2025September 2025 monthly summary for reactos/reactos: Achievements focused on strengthening test reliability and kernel stability. Key feature delivered: the CRT API tests now dynamically load functions from ntdll, crtdll, and user32, consolidating refactors to cover _sn(w)printf, _vscprintf, _vsnprintf, _vsnwprintf, wctomb, and sprintf with improved robustness and accuracy. Major bug fixes include: preventing crashes from ObInsertObject failure by avoiding double dereference and proper resource handling; closing TokenHandle on SepOpenThreadToken failure to prevent leaks; correcting NtCreateEvent prototype in the NtCreateEvent tests to align with the correct parameter type. These changes reduce flaky tests and runtime risk, contributing to more reliable builds and kernel/user-mode interoperation. Technologies and skills demonstrated include C-level test harness improvements, dynamic symbol loading, Windows NT kernel concepts, and careful resource/handle management.
September 2025
August 2025
14 Commits • 2 Features
Aug 1, 2025August 2025 focused on delivering developer-facing improvements, hardening core subsystems, and strengthening test reliability across the repository. Key work spanned kernel debugging UX, VCRUNTIME ARM64 readiness, robust exception handling paths, test infrastructure stabilization, and NPFS safety fixes. These efforts reduced release risk, improved cross-version stability, and established groundwork for faster feature delivery and performance improvements.
August 2025
14 Commits • 2 Features
Aug 1, 2025August 2025 focused on delivering developer-facing improvements, hardening core subsystems, and strengthening test reliability across the repository. Key work spanned kernel debugging UX, VCRUNTIME ARM64 readiness, robust exception handling paths, test infrastructure stabilization, and NPFS safety fixes. These efforts reduced release risk, improved cross-version stability, and established groundwork for faster feature delivery and performance improvements.
July 2025
31 Commits • 11 Features
Jul 1, 2025July 2025 performance summary for reactos/reactos: Delivered foundational runtime and portability improvements across SEH/unwind, FP state management, API/header quality, NTOS feature work, and targeted bug fixes. These changes enhance stability, cross-architecture reliability, and developer efficiency, with concrete commits driving foundational capabilities for future work.
31 Commits • 11 Features
Jul 1, 2025July 2025 performance summary for reactos/reactos: Delivered foundational runtime and portability improvements across SEH/unwind, FP state management, API/header quality, NTOS feature work, and targeted bug fixes. These changes enhance stability, cross-architecture reliability, and developer efficiency, with concrete commits driving foundational capabilities for future work.
July 2025
June 2025
15 Commits • 3 Features
Jun 1, 2025June 2025 monthly summary for reactos/reactos: Delivered key feature work, stabilized core subsystems, expanded test coverage, and improved build reliability. Highlights include GetFinalPathNameByHandleW support for KERNEL32_VISTA with comprehensive unit tests across local files, network shares, and edge cases; extensive CRT/UCRT API test suites for log, logf, log10, sin/sinf, tan/tanf, and isnan/isnanf with SSE2 variants; and ongoing maintenance to improve test stability and portability.
June 2025
15 Commits • 3 Features
Jun 1, 2025June 2025 monthly summary for reactos/reactos: Delivered key feature work, stabilized core subsystems, expanded test coverage, and improved build reliability. Highlights include GetFinalPathNameByHandleW support for KERNEL32_VISTA with comprehensive unit tests across local files, network shares, and edge cases; extensive CRT/UCRT API test suites for log, logf, log10, sin/sinf, tan/tanf, and isnan/isnanf with SSE2 variants; and ongoing maintenance to improve test stability and portability.
May 2025
67 Commits • 34 Features
May 1, 2025May 2025 Monthly Summary (reactos/reactos): Focused on delivering core platform capabilities, stabilizing tests, and improving localization and math performance. The work emphasizes business value: improved runtime feature detection, internationalization support, and robust test coverage across components used by Windows compatibility layers and apps.
67 Commits • 34 Features
May 1, 2025May 2025 Monthly Summary (reactos/reactos): Focused on delivering core platform capabilities, stabilizing tests, and improving localization and math performance. The work emphasizes business value: improved runtime feature detection, internationalization support, and robust test coverage across components used by Windows compatibility layers and apps.
May 2025
April 2025
20 Commits • 6 Features
Apr 1, 2025April 2025: Major stability and quality improvements across core subsystems. Implemented APIC interrupt reliability enhancements, stabilized Rich Edit behavior on MSVC i386, hardened MSVC build configurations, expanded API test coverage (NtQuerySection/NtQueryObject) with fixes, and added CRT rounding support with a robust math test suite, delivering measurable business value through fewer regressions and improved platform compatibility.
April 2025
20 Commits • 6 Features
Apr 1, 2025April 2025: Major stability and quality improvements across core subsystems. Implemented APIC interrupt reliability enhancements, stabilized Rich Edit behavior on MSVC i386, hardened MSVC build configurations, expanded API test coverage (NtQuerySection/NtQueryObject) with fixes, and added CRT rounding support with a robust math test suite, delivering measurable business value through fewer regressions and improved platform compatibility.
March 2025
8 Commits • 2 Features
Mar 1, 2025March 2025 focused on stabilizing boot paths, expanding observability, and modernizing internal APIs. Delivered hardware boot stability fixes for VMware and bare-metal interrupt handling; introduced profiling infrastructure and aligned x64 tests; completed internal API cleanups and header refactors with improved memory alignment. These changes reduce boot failures, enable better performance diagnostics, and improve maintainability and test reliability, laying groundwork for faster future iterations.
8 Commits • 2 Features
Mar 1, 2025March 2025 focused on stabilizing boot paths, expanding observability, and modernizing internal APIs. Delivered hardware boot stability fixes for VMware and bare-metal interrupt handling; introduced profiling infrastructure and aligned x64 tests; completed internal API cleanups and header refactors with improved memory alignment. These changes reduce boot failures, enable better performance diagnostics, and improve maintainability and test reliability, laying groundwork for faster future iterations.
March 2025
February 2025
13 Commits • 4 Features
Feb 1, 2025February 2025 monthly summary for reactos/reactos focusing on Windows compatibility, internationalization, and runtime stability, complemented by expanded cross-platform testing. The work delivers stronger API compatibility across WS2_32 and CRT, enhanced locale support for globalization, and increased reliability through broader test coverage, driven by a structured commit stream and cross-repo collaboration.
February 2025
13 Commits • 4 Features
Feb 1, 2025February 2025 monthly summary for reactos/reactos focusing on Windows compatibility, internationalization, and runtime stability, complemented by expanded cross-platform testing. The work delivers stronger API compatibility across WS2_32 and CRT, enhanced locale support for globalization, and increased reliability through broader test coverage, driven by a structured commit stream and cross-repo collaboration.
January 2025
33 Commits • 13 Features
Jan 1, 2025January 2025 performance summary for reactos/reactos: Focused on stability, compatibility, and build-system modernization across core runtime components, user-mode services, and development tooling. Delivered key features, addressed high-impact bugs, and advanced Windows compatibility with improved compiler and build support to accelerate downstream features and CI feedback. Key features delivered include WKSSVC: NetrWkstaUserGetInfo enhancements with level 1101 support, memory-leak fixes, corrected error signaling, and improved formatting. Core runtime and startup improvements established a foundation for incremental builds and modularization: UCRT/VCRUNTIME runtime helpers and init stubs; VCRUNTIME/VCSTARTUP separation into distinct libraries; and initial UCRTBASE and NDK enhancements. Additional build-automation and compatibility work included CMake defaults for host tools to Debug, support for WITH_DBG/NO_DBG overrides, and GCC-specific _CRT_SUPPRESS_RESTRICT wiring. Other notable feature work: URLMON: PROXY_CLSID_IS on the command line and NDK: FILE_MODE_INFORMATION. Major bugs fixed include BROWSEUI: validating ATL windows before destruction to prevent crashes; VCRUNTIME: GCC emmintrin.h compatibility fixes; MSHTML_WINETEST: crash in ActiveX path; NTOS:MM: MmCreatePeb process affinity fix; RSYM64 cleanup by removing deprecated RSYM64 path; MSVCRT_WINETEST: alignment to wine-10.0; Windows 2003 compatibility fixes; CRT: NAN macro; RTL/x64: RtlpUnwindInternal bug fix; FREELDR: PC98 build fix. Overall impact and accomplishments: Improved runtime stability and Windows compatibility, reduced crash surfaces, and enhanced build reliability and modularization, enabling faster integration of downstream features. The work positions the project to support incremental builds, broader compiler support, and more maintainable runtime libraries while delivering tangible business value for downstream Windows compatibility and developer productivity. Technologies/skills demonstrated: C/C++, Windows internals, cross-platform and cross-compiler compatibility (GCC), memory management and leak remediation, runtime initialization and cleanup patterns, build-system automation (CMake), modular library design, and test stabilization across Windows-specific components.
33 Commits • 13 Features
Jan 1, 2025January 2025 performance summary for reactos/reactos: Focused on stability, compatibility, and build-system modernization across core runtime components, user-mode services, and development tooling. Delivered key features, addressed high-impact bugs, and advanced Windows compatibility with improved compiler and build support to accelerate downstream features and CI feedback. Key features delivered include WKSSVC: NetrWkstaUserGetInfo enhancements with level 1101 support, memory-leak fixes, corrected error signaling, and improved formatting. Core runtime and startup improvements established a foundation for incremental builds and modularization: UCRT/VCRUNTIME runtime helpers and init stubs; VCRUNTIME/VCSTARTUP separation into distinct libraries; and initial UCRTBASE and NDK enhancements. Additional build-automation and compatibility work included CMake defaults for host tools to Debug, support for WITH_DBG/NO_DBG overrides, and GCC-specific _CRT_SUPPRESS_RESTRICT wiring. Other notable feature work: URLMON: PROXY_CLSID_IS on the command line and NDK: FILE_MODE_INFORMATION. Major bugs fixed include BROWSEUI: validating ATL windows before destruction to prevent crashes; VCRUNTIME: GCC emmintrin.h compatibility fixes; MSHTML_WINETEST: crash in ActiveX path; NTOS:MM: MmCreatePeb process affinity fix; RSYM64 cleanup by removing deprecated RSYM64 path; MSVCRT_WINETEST: alignment to wine-10.0; Windows 2003 compatibility fixes; CRT: NAN macro; RTL/x64: RtlpUnwindInternal bug fix; FREELDR: PC98 build fix. Overall impact and accomplishments: Improved runtime stability and Windows compatibility, reduced crash surfaces, and enhanced build reliability and modularization, enabling faster integration of downstream features. The work positions the project to support incremental builds, broader compiler support, and more maintainable runtime libraries while delivering tangible business value for downstream Windows compatibility and developer productivity. Technologies/skills demonstrated: C/C++, Windows internals, cross-platform and cross-compiler compatibility (GCC), memory management and leak remediation, runtime initialization and cleanup patterns, build-system automation (CMake), modular library design, and test stabilization across Windows-specific components.
January 2025
December 2024
28 Commits • 13 Features
Dec 1, 2024December 2024 ReactOS development summary for the reactos/reactos repository. The month focused on strengthening runtime libraries (UCRT, CRT, VCRUNTIME), stabilizing low-level kernel/User-mode components, and improving the build pipeline. This delivered concrete business value through a more reliable build, improved runtime compatibility, and enhanced kernel/user collaboration across subsystems. Key features delivered: - CMake Build Configuration: Build host-tools as release by default. (commit 8a63d7e89865ce5c4ef03a4dd133b22564382606) - UCRT MATH: Implement _dtest and _fdtest. (commit 9f15d9ee5784d607bbeaab69302f4d7190a8b52c) - UCRT LOCALE: Implement __acrt_MultiByteToWideChar and __acrt_WideCharToMultiByte. (commits bd3c7654ec5483e735d46b238a262c617eadca6d, d21fd3765078594e07543840e5dd835df1994111) - UCRT/VCRUNTIME: Initialization helpers and ISA availability, plus startup stub. (commits 8aab548ecdd7bb5230ad774fb8df09cb15c9ac76, 9c887efa0e90bcc5a516ebea902366398708e65f, 446234207603320f29d98852d73f1fdd930405f8) - CRT MATH: Implement _finite and _finitef. (commit e01231bd4998bf3300efe2aab14293ffac51c494) Major bugs fixed: - IERNONCE: Check m_RegKey before deleting a value to avoid invalid deletions. (commit 40b45515a40bf29cf6ed1a4ad1eaedf7ad3ae281) - EXPLORER-OLD: Fix build when _DEBUG is defined. (commit c2c4d853c2bd31a6abf7b5dc7b54814bae12a712) - NTOS/HAL: Interrupt handling fixes across KiInterruptDispatch, KiEoiHelper removal, and clock-handler call paths. (commits 67231bd69ab9b66cc14d92b8ff33d1ffe197392f, 1f647e447985c839c2c51d3c0436e9f9ce430cd2, 5ebd4783257270ea50dcc02babacd56a6623bce8) - WIN32K: Fixed crash/undefined behavior when desktop window is NULL during mouse message processing. (commit 2d4c0b87b1eccecbdd220ef9dea6512bbeb2fcd8) - NTOS KE/x64: Unwind handling and User State fixes to improve reliability in AP stack unwinding and user state management. (commits 29721ac552cd104116bbc197b8df1782c72f7710, 0fc0d9ebb178462c2f338c78a47f1773f3770576, 91948dea80126028a05e3ee83f9857d06ed5370f) Overall impact and accomplishments: - Strengthened core runtime support, delivering more complete UCRT/CRT/VCRUNTIME implementations and safer initialization paths, which improves downstream stability for applications relying on these libraries. - Improved build reliability and developer experience with a release-by-default host-tools build, reducing friction for release checks and CI pipelines. - Cross-subsystem stabilization in NTOS/UX areas (HAL, KEx, TEB, and input handling) contributing to more predictable crash behavior, easier debugging, and better platform compatibility. Technologies and skills demonstrated: - Build systems: CMake defaults and host-tools packaging improvements. - Runtime libraries: UCRT, CRT, VCRUNTIME improvements and aliasing for clang builtins. - Low-level OS/kernel work: NTOS, HAL, NTUSER, and input handling fixes; x64 unwind, user-state handling, and stack-protection considerations. - Code quality and maintainability: startup uninitialization stubs, private API encapsulation, and improved debugging/build configurations.
December 2024
28 Commits • 13 Features
Dec 1, 2024December 2024 ReactOS development summary for the reactos/reactos repository. The month focused on strengthening runtime libraries (UCRT, CRT, VCRUNTIME), stabilizing low-level kernel/User-mode components, and improving the build pipeline. This delivered concrete business value through a more reliable build, improved runtime compatibility, and enhanced kernel/user collaboration across subsystems. Key features delivered: - CMake Build Configuration: Build host-tools as release by default. (commit 8a63d7e89865ce5c4ef03a4dd133b22564382606) - UCRT MATH: Implement _dtest and _fdtest. (commit 9f15d9ee5784d607bbeaab69302f4d7190a8b52c) - UCRT LOCALE: Implement __acrt_MultiByteToWideChar and __acrt_WideCharToMultiByte. (commits bd3c7654ec5483e735d46b238a262c617eadca6d, d21fd3765078594e07543840e5dd835df1994111) - UCRT/VCRUNTIME: Initialization helpers and ISA availability, plus startup stub. (commits 8aab548ecdd7bb5230ad774fb8df09cb15c9ac76, 9c887efa0e90bcc5a516ebea902366398708e65f, 446234207603320f29d98852d73f1fdd930405f8) - CRT MATH: Implement _finite and _finitef. (commit e01231bd4998bf3300efe2aab14293ffac51c494) Major bugs fixed: - IERNONCE: Check m_RegKey before deleting a value to avoid invalid deletions. (commit 40b45515a40bf29cf6ed1a4ad1eaedf7ad3ae281) - EXPLORER-OLD: Fix build when _DEBUG is defined. (commit c2c4d853c2bd31a6abf7b5dc7b54814bae12a712) - NTOS/HAL: Interrupt handling fixes across KiInterruptDispatch, KiEoiHelper removal, and clock-handler call paths. (commits 67231bd69ab9b66cc14d92b8ff33d1ffe197392f, 1f647e447985c839c2c51d3c0436e9f9ce430cd2, 5ebd4783257270ea50dcc02babacd56a6623bce8) - WIN32K: Fixed crash/undefined behavior when desktop window is NULL during mouse message processing. (commit 2d4c0b87b1eccecbdd220ef9dea6512bbeb2fcd8) - NTOS KE/x64: Unwind handling and User State fixes to improve reliability in AP stack unwinding and user state management. (commits 29721ac552cd104116bbc197b8df1782c72f7710, 0fc0d9ebb178462c2f338c78a47f1773f3770576, 91948dea80126028a05e3ee83f9857d06ed5370f) Overall impact and accomplishments: - Strengthened core runtime support, delivering more complete UCRT/CRT/VCRUNTIME implementations and safer initialization paths, which improves downstream stability for applications relying on these libraries. - Improved build reliability and developer experience with a release-by-default host-tools build, reducing friction for release checks and CI pipelines. - Cross-subsystem stabilization in NTOS/UX areas (HAL, KEx, TEB, and input handling) contributing to more predictable crash behavior, easier debugging, and better platform compatibility. Technologies and skills demonstrated: - Build systems: CMake defaults and host-tools packaging improvements. - Runtime libraries: UCRT, CRT, VCRUNTIME improvements and aliasing for clang builtins. - Low-level OS/kernel work: NTOS, HAL, NTUSER, and input handling fixes; x64 unwind, user-state handling, and stack-protection considerations. - Code quality and maintainability: startup uninitialization stubs, private API encapsulation, and improved debugging/build configurations.
November 2024
43 Commits • 10 Features
Nov 1, 2024November 2024 monthly summary for reactos/reactos: Focused on stabilizing builds, expanding portability, and enhancing upstream alignment to maximize business value for downstream developers and end-users. Delivered cross-compiler compatibility fixes, build-system hardening, and portability improvements across UCRT/CRT, PSEH, MATH, and core components, enabling more reliable contributions and broader platform support. Results include improved GCC/Clang compatibility, better clang-cl/MSVC handling, and alignment with wine-7.0 for upstream compatibility, reducing maintenance cost and accelerating delivery of higher-quality releases.
43 Commits • 10 Features
Nov 1, 2024November 2024 monthly summary for reactos/reactos: Focused on stabilizing builds, expanding portability, and enhancing upstream alignment to maximize business value for downstream developers and end-users. Delivered cross-compiler compatibility fixes, build-system hardening, and portability improvements across UCRT/CRT, PSEH, MATH, and core components, enabling more reliable contributions and broader platform support. Results include improved GCC/Clang compatibility, better clang-cl/MSVC handling, and alignment with wine-7.0 for upstream compatibility, reducing maintenance cost and accelerating delivery of higher-quality releases.
November 2024
October 2024
8 Commits • 3 Features
Oct 1, 2024Month 2024-10 — Focused on core UCRT improvements in reactos/reactos, delivering migration to ucrtbase.dll, internal runtime enhancements, and test framework integration to improve compatibility and robustness. The work strengthens runtime alignment with modern Windows environments and expands test coverage for future reliability.
October 2024
8 Commits • 3 Features
Oct 1, 2024Month 2024-10 — Focused on core UCRT improvements in reactos/reactos, delivering migration to ucrtbase.dll, internal runtime enhancements, and test framework integration to improve compatibility and robustness. The work strengthens runtime alignment with modern Windows environments and expands test coverage for future reliability.
Activity
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Quality Metrics
Correctness90.4%
Maintainability89.2%
Architecture85.8%
Performance81.2%
AI Usage20.0%
Skills & Technologies
Programming Languages
AssemblyCC++CMakePythonXMLcmakeinf
Technical Skills
x86-64 AssemblyAPI DevelopmentAPI TestingAPI developmentARM ArchitectureARM64Algorithm implementationAssemblyAssembly (implied)Assembly LanguageAssembly ProgrammingAssembly Syntax ConfigurationAssembly languageBit manipulationBootloader Development
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