Cesarus85--mjolnir-vr/docs/object_matching_logs/libcmt_freebuf_obj.md

libs/libcmt/_freebuf.obj exact-match ledger

This is an atomic reconstruction lane created from authoritative campaign commit 91ee86cd. Before editing, the unit was confirmed MISSING, absent from config/parked.json, absent from every active worktree, and unclaimed by the other active agents.

Plain-English behavior

_freebuf releases a C stream's buffer only when the stream is open and the runtime itself owns that buffer. It calls free on the stream's typed FILE._base pointer, clears both the public _IOMYBUF ownership flag and the CRT-private flag recording a setvbuf buffer, then resets _ptr, _base, and _cnt. Streams that are closed or do not own their buffer are left unchanged.

Primary provenance

The primary source of truth is member _freebuf.obj extracted directly from the XDK 3911 libcmt.lib, not a later CRT or community reconstruction. Its runtime .text is strictly identical to the January target before any source work:

• function __freebuf, 43 bytes;
• one REL32 relocation at function offset +0x14, targeting _free + 0;
• normalized SHA-256 fe3ca156c86d0bfc8465c0ae848bfcbc00c3a00ab033378839fc7eaf212a583f;
• no owned runtime .data, .bss, or .rdata.

The archive member identifies its original source as d:\xbox-finalfre\private\sdktools\crt\crtw32\stdio\_freebuf.c. Its ordinary C function and line records (.bf, .lf, and .ef) prove this is compiled C, not handwritten or vendored assembly. The XDK's public stdio.h proves the complete FILE layout and the _IOREAD, _IOWRT, _IORW, and _IOMYBUF values. The remaining _IOSETVBUF flag is private to the CRT; the January/XDK instruction clearing 0x0408, together with the historical CRT internal-header name, proves its value 0x0400 and its set-buffer role.

Source-shape experiment record

ID	Readable C shape	Measured result
E01	Typed FILE *; combined open-state test followed by _IOMYBUF; free _base; clear the two flags; chained null assignment for _ptr and _base; zero _cnt	Correct 43-byte size and relocation, but the C assignment chain wrote _base before _ptr; January writes _ptr first
E02	Replace only the chained null assignment with explicit _ptr = 0; followed by _base = 0;	Strict exact. Target and candidate are 43/43 bytes with the same one relocation and normalized SHA-256; directly reflects January's measured store order

No assembly, byte patch, opaque structure offset, undefined behavior, volatile, forced inline, optimization pragma, or compiler-flag change is permitted in this lane.

Strict verification

XDK 3911 CL.Exe 13.00.9254.1 rebuilt the final source under the generated /O1 /Gy /I"xbox/include" flags. The January target, candidate, and extracted XDK archive member agree on every runtime property:

• 43/43/43 code bytes and one function;
• one REL32 relocation at +0x14, resolving to external _free + 0;
• normalized SHA-256 fe3ca156c86d0bfc8465c0ae848bfcbc00c3a00ab033378839fc7eaf212a583f;
• external function symbol __freebuf at offset zero, type 0x20, storage class 2;
• one 43-byte executable COMDAT with flags 0x60101020 and no owned runtime data section.

section_infos_equal is true for target versus candidate. The archive member's additional compiler, debug, and build-number sections are removable metadata, not runtime source ownership.

Current-campaign gates passed:

• forced full halobetacache_build and libcmt_build;
• regenerated semantic_progress with zero unit errors;
• progress, crediting 43 libcmt code bytes, one function, and one complete object;
• semantic audit with zero unit errors and both objdiff and semantic-coff proof for __freebuf;
• admission audit with no _freebuf contradiction, candidate, or revocation;
• 179/179 tool unit tests;
• git diff --check.

The clean-commit whole-object regression snapshot/check passed after a forced rebuild: __freebuf is still_exact, with no changed-nonexact function, no newly-exact ambiguity, no warning, and no ownership change.

House/Berth, readability, and bug audit

The implementation uses the XDK's real FILE type, named fields, public stream flags, and the historically named private _IOSETVBUF flag. The parameter is on its own line and has an ordinary typed declaration. (void) is inapplicable because the function takes a parameter. There are no Halo tag, datum, or object accesses requiring project-specific accessors.

No assembly, volatile, forced inlining, undefined behavior, byte patch, alignment directive, optimization pragma, raw offset, comparator exception, or codegen-only cast is used. No original January bug was found, so no bug-preservation comment or disabled corrected form is needed.