`libs/libcmt/_open.obj` exact-match ledger

Plain-English behavior

_openfile translates a mode string such as "rb+" into the low-level flags used by _sopen. It rejects an invalid leading mode, prevents duplicate or contradictory modifiers, opens the file with the caller's sharing mode, and initializes the supplied FILE record after a successful open.

Scope and provenance

Atomic base: fc8e1b076965ed489f291ee233eaad3e1ffaf419.
XDK 3911 CL 13.00.9254.1; unchanged libcmt flags /O1 /Gy.
Primary member: obj\i386\_open.obj from XDK 3911 libcmt.lib, archive SHA-256 60aa4c87c97eeb6662b31d9d37cf3caba1afabaec72c47b090e7a0ce8b632f55.
CodeView names ordinary Microsoft C at d:\xbox-finalfre\private\sdktools\crt\crtw32\stdio\_open.c.
The corresponding completed _wopen.obj is used only as a topology donor; January and the authenticated narrow archive member remain authoritative.

The archive member is strict-identical to January before reconstruction. The whole runtime object is one external COMDAT, __openfile: 360 bytes, three relocations (__commode, __sopen, and __cflush), normalized SHA-256 bad2621670a65578e7fe2165d89d5fb41ee6af36cf41af9f235599db4fdb72e6. It owns no .data, .bss, or .rdata.

Experiment ledger

ID	Source shape	Result	Decision
E01	Authenticated Microsoft parser topology specialized to `char`, with the validity flag assigned immediately before the loop	Exact 360/360 bytes, 3/3 relocations, identical normalized SHA-256 and destinations	Accepted

The accepted first compile also confirms the neighboring _wopen.obj finding: delaying valid = 1 until immediately before the scan keeps its live range short enough for VC7 to retain it in a register. Initializing it at the declaration would unnecessarily overlap the two duplicate-option locals.

Strict validation

Forced rebuild under unchanged /O1 /Gy: passed.
__openfile: exact normalized SHA-256 bad2621670a65578e7fe2165d89d5fb41ee6af36cf41af9f235599db4fdb72e6.
Relocations match exactly at +0x09 -> __commode, +0x138 -> __sopen, and +0x14E -> __cflush.
Whole runtime inventory: one 360-byte external code COMDAT and no owned .data, .bss, or .rdata, matching January and the XDK member.
Full halobetacache_build and libcmt_build: passed.
Progress: 364/833 objects overall; libcmt 97/212 objects, 155/476 functions, and 11,681/55,015 code bytes.
Semantic report: 465 units, 3,592 functions evaluated, 3,508 accepted exact, and zero unit errors.
Admission audit: zero candidates, zero revocations, and only the known pre-existing source/shell/shell_xbox contradiction.
Tool suite: 179/179 tests passed.
Config JSON, prohibited-construct scan, and git diff --check: passed.
Clean-commit per-unit regression snapshot/check: __openfile remains still_exact; no failures, warnings, newly exact, or changed-nonexact functions. No historical artifact is used to grant credit.

Original-bug audit

No independently actionable bug is established. The historical parser stops at the first invalid or duplicate modifier but still opens using the valid prefix. That is original CRT behavior and is preserved rather than silently "fixed".

House/Berth audit

Readable typed C, named _O_* and FILE fields, semantic local names.
No assembly, volatile, forced inline, compiler pragma, UB, byte forcing, opaque codegen cast, flag change, or comparator exception.
The original mode grammar, call order, failure behavior, and FILE initialization order are preserved.
Matching credit is conditional on full strict bytes, relocations, ownership, regression, semantic/admission, build, test, and diff gates.

3.7 KiB Raw Blame History

libs/libcmt/_open.obj exact-match ledger