[UDFS] Remove legacy x86 asm string-length paths in favor of shared C/C++ implementation by Copilot · Pull Request #277 · Zero3K20/reactos

Copilot · 2026-04-19T03:05:33Z

Reset HEAD to pre-merge commit (remove old merge commit from local branch)
Rebased copilot commits (Initial plan, [UDFS] remove legacy x86 asm, [UDFS] Remove all inline assembly, fix: review feedback, fix: USHORT cast precedence) onto origin/udf-dev, skipping the two pre-existing Gleb Lamm refactoring commits that are superseded by udf-dev
Resolved all Sys_spec_lib.cpp conflicts by keeping udf-dev's version (udf-dev already removed those functions; equivalent changes were auto-applied to string_lib.cpp where the functions now live)
The rebased tree state is functionally identical to the old merge-commit state — only a trailing newline difference in Sys_spec_lib.cpp
Push updated branch (fast-forward commit syncing tree to rebased state)

Agent-Logs-Url: https://github.com/Zero3K20/reactos/sessions/e6c55273-aa26-46f7-800d-d886684328b6 Co-authored-by: Zero3K20 <258969903+Zero3K20@users.noreply.github.com>

Agent-Logs-Url: https://github.com/Zero3K20/reactos/sessions/9391a902-dd88-4c82-bf33-9e94fdacb804 Co-authored-by: Zero3K20 <258969903+Zero3K20@users.noreply.github.com>

Copilot

Pull request overview

This PR modernizes the UDFS driver’s debug/breakpoint and “touch” helpers by removing legacy x86 inline-asm code paths and standardizing on shared C/C++ implementations.

Changes:

Replaced x86 __asm int 3 / INT3 usage with __debugbreak() in multiple debug/bounds-check paths.
Removed x86 inline-asm implementations for “touch” helpers, keeping a single C implementation.
Removed x86 inline-asm “string length scan” implementations, keeping the generic C loop.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
drivers/filesystems/udfs/udf_dbg.h	Uses `__debugbreak()` for breakpoints; drops x86 asm `UDFTouch()` path in favor of a single C implementation.
drivers/filesystems/udfs/Include/mem_tools.cpp	Drops x86 asm `DbgTouch()` path in favor of a single C implementation.
drivers/filesystems/udfs/Include/mem_tools.h	Replaces inline-asm INT3 breakpoints in debug/bounds-check helpers with `__debugbreak()`.
drivers/filesystems/udfs/Include/string_lib.cpp	Removes x86 asm string-length scanning, leaving the generic loop.
drivers/filesystems/udfs/Include/Sys_spec_lib.cpp	Removes x86 asm string-length scanning, leaving the generic loop.

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Zero3K20 · 2026-04-19T04:18:35Z

@copilot apply changes based on the comments in this thread

…d in string scans Agent-Logs-Url: https://github.com/Zero3K20/reactos/sessions/3f27bce7-3456-4448-a1b3-0b63c30b4cc7 Co-authored-by: Zero3K20 <258969903+Zero3K20@users.noreply.github.com>

Agent-Logs-Url: https://github.com/Zero3K20/reactos/sessions/3f27bce7-3456-4448-a1b3-0b63c30b4cc7 Co-authored-by: Zero3K20 <258969903+Zero3K20@users.noreply.github.com>

Copilot · 2026-04-19T04:22:51Z

@copilot apply changes based on the comments in this thread

Applied all six review suggestions in commit 66f773c7, with a follow-up cast-precedence fix in a68deb76:

DbgTouch() (mem_tools.cpp): read through volatile UCHAR* into a volatile UCHAR a so the load cannot be eliminated by the optimizer.
UDFTouch() (udf_dbg.h): read through volatile UCHAR* to guarantee the memory access is emitted.
Four NUL-terminator scan loops in string_lib.cpp and Sys_spec_lib.cpp: widened loop counter from USHORT to ULONG, added i < (MAXUSHORT / sizeof(WCHAR)) upper-bound guard to prevent wraparound infinite loops, and added correctly parenthesised (USHORT) casts on Length/MaximumLength assignments.

… __debugbreak() Agent-Logs-Url: https://github.com/Zero3K20/reactos/sessions/c974a8bc-1af0-4576-a1db-2cba7bd89376 Co-authored-by: Zero3K20 <258969903+Zero3K20@users.noreply.github.com>

…f-dev

Zero3K20 · 2026-04-27T15:26:45Z

@copilot Please fix the conflicts.

…mance Resolve conflicts: - Sys_spec_lib.cpp: removed commented-out block (base branch refactored, kept new functions) - udf_dbg.h: keep __debugbreak() over legacy __asm int 3 (our PR change) Co-authored-by: Zero3K20 <258969903+Zero3K20@users.noreply.github.com>

Copilot · 2026-04-27T15:34:34Z

@copilot Please fix the conflicts.

Resolved in merge commit 4059a000. All 23 conflicted files were addressed:

Non-PR files (cleanup, close, create, env_spec, etc.): took the base branch (udf-dev) version
udf_dbg.h: kept our __debugbreak() macro over the reverted __asm int 3 from the base branch
Sys_spec_lib.cpp: base branch removed MyAppendUnicodeToString_ / MyInitUnicodeString entirely as part of its refactoring, so the commented-out block from our branch was dropped accordingly

Agent-Logs-Url: https://github.com/Zero3K20/reactos/sessions/c60a5f35-f71d-435d-916f-3de11d690240 Co-authored-by: Zero3K20 <258969903+Zero3K20@users.noreply.github.com>

#302, #304, #306, #308, #310, #316, #335, #339 Agent-Logs-Url: https://github.com/Zero3K20/reactos/sessions/c135164e-e9f3-4164-ba64-d04f8a2dd19a Co-authored-by: Zero3K20 <258969903+Zero3K20@users.noreply.github.com>

assorted and others added 5 commits December 25, 2025 18:46

refactoring

b9d68f3

try-fix-write

a3a7243

refactoring

cffe655

UDFInsertPrefix

a3305a9

Initial plan

b1c40c0

Copilot AI assigned Copilot and Zero3K20 Apr 19, 2026

Copilot started work on behalf of Zero3K20 April 19, 2026 03:05 View session

Copilot AI linked an issue Apr 19, 2026 that may be closed by this pull request

[UDFS] Is the assembly being used in its code actually faster than the C/C++ code that is after the else line? #276

Open

[UDFS] remove legacy x86 asm string-length micro-optimizations

e1ee3b3

Agent-Logs-Url: https://github.com/Zero3K20/reactos/sessions/e6c55273-aa26-46f7-800d-d886684328b6 Co-authored-by: Zero3K20 <258969903+Zero3K20@users.noreply.github.com>

Copilot AI changed the title ~~[WIP] Analyze performance of assembly versus C/C++ code~~ [UDFS] Remove legacy x86 asm string-length paths in favor of shared C/C++ implementation Apr 19, 2026

Copilot AI requested a review from Zero3K20 April 19, 2026 03:08

Copilot finished work on behalf of Zero3K20 April 19, 2026 03:08

Copilot started work on behalf of Zero3K20 April 19, 2026 03:09 View session

Copilot finished work on behalf of Zero3K20 April 19, 2026 03:12

Copilot started work on behalf of Zero3K20 April 19, 2026 03:15 View session

Copilot finished work on behalf of Zero3K20 April 19, 2026 03:17

Copilot started work on behalf of Zero3K20 April 19, 2026 03:24 View session

[UDFS] Remove all inline assembly from the driver

6614940

Agent-Logs-Url: https://github.com/Zero3K20/reactos/sessions/9391a902-dd88-4c82-bf33-9e94fdacb804 Co-authored-by: Zero3K20 <258969903+Zero3K20@users.noreply.github.com>

Copilot finished work on behalf of Zero3K20 April 19, 2026 03:28

Copilot started work on behalf of Zero3K20 April 19, 2026 03:55 View session

Copilot finished work on behalf of Zero3K20 April 19, 2026 03:57

Zero3K20 requested a review from Copilot April 19, 2026 04:05

Copilot started reviewing on behalf of Zero3K20 April 19, 2026 04:05 View session

Copilot AI reviewed Apr 19, 2026

View reviewed changes

Copilot started work on behalf of Zero3K20 April 19, 2026 04:18 View session

Copilot AI and others added 2 commits April 19, 2026 04:21

fix: address review feedback - volatile touch reads, USHORT wraparoun…

66f773c

…d in string scans Agent-Logs-Url: https://github.com/Zero3K20/reactos/sessions/3f27bce7-3456-4448-a1b3-0b63c30b4cc7 Co-authored-by: Zero3K20 <258969903+Zero3K20@users.noreply.github.com>

fix: correct USHORT cast precedence in MaximumLength assignments

a68deb7

Agent-Logs-Url: https://github.com/Zero3K20/reactos/sessions/3f27bce7-3456-4448-a1b3-0b63c30b4cc7 Co-authored-by: Zero3K20 <258969903+Zero3K20@users.noreply.github.com>

Copilot finished work on behalf of Zero3K20 April 19, 2026 04:23

Zero3K20 mentioned this pull request Apr 19, 2026

[UDFS] Fix C bool literals, add typedef aliases, remove legacy x86 asm paths, thread PH_TMP_BUFFER through sector I/O, and add chunked bitmap infrastructure #275

Closed

Merge branch 'udf-dev' of https://github.com/zero3k20/reactos into ud…

991f517

…f-dev

Zero3K20 changed the base branch from write to udf-dev April 27, 2026 06:58

Copilot started work on behalf of Zero3K20 April 27, 2026 15:26 View session

Copilot finished work on behalf of Zero3K20 April 27, 2026 15:35

Copilot started work on behalf of Zero3K20 April 28, 2026 00:33 View session

Copilot finished work on behalf of Zero3K20 April 28, 2026 00:34

Copilot started work on behalf of Zero3K20 April 28, 2026 00:36 View session

rebase: add trailing newline (sync tree state with rebased branch)

980106d

Agent-Logs-Url: https://github.com/Zero3K20/reactos/sessions/c60a5f35-f71d-435d-916f-3de11d690240 Co-authored-by: Zero3K20 <258969903+Zero3K20@users.noreply.github.com>

Copilot finished work on behalf of Zero3K20 April 28, 2026 00:47

This was referenced Apr 30, 2026

[WIP] Apply all open pull requests #337

Closed

[UDFS] Revert recent commits and apply PR #360 geometry fixes #342

Closed

Zero3K20 force-pushed the udf-dev branch from 991f517 to d0c6f32 Compare May 25, 2026 19:23

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[UDFS] Remove legacy x86 asm string-length paths in favor of shared C/C++ implementation#277

[UDFS] Remove legacy x86 asm string-length paths in favor of shared C/C++ implementation#277
Copilot wants to merge 12 commits into
udf-devfrom
copilot/udfs-compare-assembly-c-code-performance

Copilot AI commented Apr 19, 2026 •

edited

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Pull request overview

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Zero3K20 commented Apr 19, 2026

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Copilot AI commented Apr 19, 2026 •

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