Cesarus85--mjolnir-vr/docs/object_matching_logs/libcmt_crt0msg_obj.md

libs/libcmt/crt0msg.obj exact-match ledger

This atomic lane starts from campaign commit b831acac. At lane start the object was MISSING, absent from config/parked.json, and had no production source or object ledger. The January split target contains three routines, one 144-byte message lookup table, one 4-byte callback variable, and seventeen owned message strings.

Plain-English behavior

This object is the small Xbox runtime-error reporter. _NMSG_WRITE searches a table for an error number and sends the corresponding text to the Xbox debug output. _GET_RTERRMSG performs the same lookup and returns the message pointer. _FF_MSGBANNER prints a leading line break, invokes an optional Fortran debug callback, and prints the runtime error banner.

The table maps the familiar Microsoft runtime errors R6002 through R6028, the domain/singularity/loss-of-significance math errors, CRLF, and the banner to their exact text. Nothing here is fabricated from machine bytes: the readable table and routines come from authenticated Microsoft CRT C source.

Primary provenance and January inventory

The XDK 3911 libcmt.lib archive has SHA-256 60aa4c87c97eeb6662b31d9d37cf3caba1afabaec72c47b090e7a0ce8b632f55. Its actual obj\i386\crt0msg.obj member identifies ordinary C source d:\xbox-finalfre\private\sdktools\crt\crtw32\startup\crt0msg.c, compiler identifier 0x001c2426, and is independently strict-equal to the January runtime sections. The authenticated Microsoft source blob used for the reconstruction is 4733dd8a46ee4c5342befdd8ade4f537d90fd0f6.

The exact code inventory is:

Function	Bytes	Relocs	Normalized SHA-256
__NMSG_WRITE	44	4	c257a5cc8a643403707a25458d355ab70874507b7dd27466f2c421321c1bb839
__GET_RTERRMSG	42	3	10d3c4cb7a669f3771ff88ef0c28cfbc365210fa69f436a0d59ca06fef8b5f53
__FF_MSGBANNER	34	3	1fcbe9acf0bb677418f0680e0d122a3acfb3554b045b5938f6e7da30bbba0ebf

The exact non-code inventory is:

Owner	Bytes	Relocs	Normalized SHA-256
_data_00319950	144	18	25298d4d1ea85dfa6a4696577658216429876d7b7b59ed245667db872d9d79d2
__adbgmsg	4	0	df3f619804a92fdb4057192dc43dd748ea778adc52bc498ce80524c014b81119

All seventeen target-owned string COMDATs compare strict-equal individually, including their sizes, payload hashes, external storage, and section ownership. Their total payload is 727 bytes. The shared three-byte CRLF literal is undefined in the split target and defined by the rebuilt TU; the table relocation resolves to the same external COMDAT and grants no extra target-owned data credit.

Experiment matrix

ID	One changed factor	Result	Decision
E00	Compile the authenticated source with its private Microsoft includes unchanged	The repository does not contain cruntime.h, internal.h, rterr.h, or the private startup headers	Rejected as unavailable build context, not a source-shape failure
E01	Replace only unavailable private includes with standard types, declarations, and the named runtime-message constants	The host/desktop branch remained selected and referenced APIs absent from the Xbox object	Rejected; the original TU's Xbox preprocessor context was still missing
E02	Restore the source's _XBOX context while retaining the natural rterrs table name	All code and string payloads reached the January shape, but the table owner was _rterrs rather than the split target's _data_00319950	Near result; ownership spelling remained strict-nonexact
E03	Name the table data_00319950 and retain readable source references through #define rterrs data_00319950	All three functions, table, BSS, seventeen owned strings, and every relocation identity/addend are strict-exact	Accepted

The final name is not a byte-forcing trick. data_00319950 is the target's existing csplit owner and ordinary C decoration naturally emits _data_00319950. The source-level rterrs alias preserves the authenticated algorithm and readable intent.

Strict verification

XDK 3911 CL 13.00.9254.1 compiles the unit under the unchanged libcmt flags /O1 /Gy /I"xbox/include". A single hardened comparison over all three functions, both named data owners, and all seventeen target-owned strings reports all_equal: true. This includes exact normalized bytes, relocation addresses/types/destinations/addends, section flags, and owner storage.

The candidate's compiler directives and debug records are discardable metadata, not runtime ownership. The final forced object rebuild, full Halo and libcmt builds, semantic/progress audits, clean-commit regression gate, tool tests, and git diff --check are recorded after admission below.

House/Berth and original-bug audit

The production unit is authenticated readable Microsoft C with named constants, typed parameters, multiline declarations, and explicit ownership. It uses no assembly, volatile, forced inline, undefined aliasing, byte patch, opaque field offset, alignment trick, compiler-flag exception, or comparator waiver. Defining _XBOX inside this recovered private runtime source restores the original source configuration; it does not alter the project compiler command.

Both lookup routines preserve a proven original defect: an unknown runtime error number leaves the index equal to the table count and the next condition reads one record beyond the array. The authenticated source and January machine control flow independently prove that behavior. The production source marks it with the required BUG (preserved for exact matching) comments and states the safe corrected form: guard the array access with tblindx < _RTERRCNT. The exact build deliberately does not silently repair the shipped behavior.

Final gates

• Forced crt0msg.obj rebuild: passed under unchanged /O1 /Gy.
• Hardened whole-object comparison: all three functions, the 144-byte table, 4-byte BSS, and all seventeen target-owned strings are strict-exact.
• Full halobetacache_build and libcmt_build: passed.
• Semantic audit after rebasing onto the current campaign: 458 units, 3,575 functions evaluated, 3,491 accepted exact, and zero unit errors.
• Progress/admission: crt0msg.obj is credited as one complete object; its three functions contribute 120 code bytes and its table contributes 144 data bytes through a hash-pinned, fail-closed semantic-data entry.
• Tooling unit tests: 179/179 passed.
• Configuration JSON parsing and git diff --check: passed.
• Current-canonical full rebuild/progress revalidation passed: 357/833 objects overall and 90/212 libcmt objects, with 3,486/11,060 functions and 415,447/2,198,102 code bytes overall.
• The clean-commit fail-closed regression snapshot/check reports all three functions as still_exact, with no changed-nonexact/newly-exact functions, failures, or warnings.