Repository Analysis

microsoft/STL

MSVC's implementation of the C++ Standard Library.

2.5 Likely human-written View on GitHub

Analysis Overview

This report presents the forensic synthetic code analysis of microsoft/STL, a C++ project with 11,095 GitHub stars. SynthScan v2.0 examined 418,207 lines of code across 1386 source files, recording 1097 pattern matches distributed across 10 syntactic categories. The overall adjusted score of 2.5 places this repository in the Likely human-written band.

The scanner applied 160+ deterministic lexical heuristics, multi-line block detectors, abstract syntax tree depth profilers, and a cross-file Jaccard similarity matrix to construct a statistically normalised synthetic code estimate. All matches are individually weighted by severity coefficient and contextual multiplier before summation, and the resulting headline score is temporally discounted to account for the repository's development history relative to the commercial emergence of large language model coding tooling (November 2022 onward).

2.5
Adjusted Score
2.5
Raw Score
100%
Time Factor
2026-07-14
Last Push
11.1K
Stars
C++
Language
418.2K
Lines of Code
1.4K
Files
1.1K
Pattern Hits
2026-07-14
Scan Date
0.00
HC Hit Rate

What These Metrics Mean

Adjusted Score
Primary synthetic code indicator. Raw score normalised per 1,000 lines of code and multiplied by the temporal discount factor. This is the definitive comparative metric — use it to rank repositories by AI authorship density.
Raw Score
The unmodified sum of all severity-weighted, context-multiplied pattern match scores before temporal discounting. Reflects the absolute signal strength independent of when the repository was last active.
Time Factor
The temporal discount multiplier (0–100%) applied to the raw score. Repositories last updated before ChatGPT's launch (Nov 2022) receive a 5% factor. Full signal is only assigned to repositories active in the post-adoption era (Jan 2024+).
Pattern Hits
Total count of individual pattern matches across all files and categories. A high hit count with a low score may indicate a very large codebase with isolated AI snippets; a low count with a high score indicates dense, concentrated AI signatures.
HC Hit Rate
High+Critical pattern hits per file, averaged across the repository. This orthogonal signal catches repositories where a few files are densely packed with high-severity AI tells — a strong indicator even when the normalised score appears moderate due to codebase size.
Lines of Code / Files
Total lines and files analysed. The scanner examines 94 file extensions. These denominators are used to normalise the score, enabling fair comparison between repositories of vastly different sizes.

Score History

This chart maps the temporal evolution of the adjusted synthetic code score across successive scan runs. An upward trajectory indicates ongoing incorporation of AI-generated code or expanding LLM-assisted scaffolding; a stable or declining trajectory may reflect active human refactoring, code removal, or the adoption of stricter authorship policies. The dashed secondary line (right axis) independently tracks total raw pattern hit count, which can diverge from the normalised score when codebase size changes significantly between scans.

Severity Breakdown

Classifies detected patterns by their diagnostic confidence and structural impact. CRITICAL patterns (coefficient 10) represent definitive synthetic signatures — hallucinated imports, explicit LLM attribution metadata — virtually never produced by human authors. HIGH (5) indicates strong structural tells such as cross-file repetition or cross-linguistic idioms. MEDIUM (2) covers recognisable conversational padding and AI-specific vocabulary. LOW (1) captures subtle indicators like tautological comments and generic boilerplate that require density to carry independent signal.

CRITICAL 0HIGH 0MEDIUM 6LOW 1091

Directory Score Breakdown

This horizontal bar chart decomposes the repository's raw synthetic code score by top-level directory, allowing you to pinpoint precisely which modules or components carry the highest AI authorship density. Directories with disproportionately high scores relative to their size warrant targeted manual review: concentrated AI signatures often trace back to mass-generated configuration layers, auto-ported test suites, LLM-scaffolded boilerplate classes, or entire subsystems authored under heavy copilot assistance. Use this view to prioritise your human code-review effort.

Pattern Findings

The scanner identified 1097 distinct pattern matches across 10 syntactic categories. Each entry below represents a discrete location in the source code where the engine recorded a statistically significant AI authorship indicator. Expand any category row to inspect the individual file paths, line numbers, code snippets, and the lexical context (CODE, COMMENT, or STRING) in which each match was detected.

Reading the findings table: The Severity column indicates the diagnostic confidence level (CRITICAL / HIGH / MEDIUM / LOW). The Context column identifies whether the match occurred inside executable code, an inline comment, or a string literal — comment-context matches receive a ×1.5 weight because LLMs systematically over-annotate. The ⚡ bolt icon marks clustered matches: three or more patterns within a 10-line window, each receiving an additional ×1.5 density multiplier as dense clusters constitute far stronger evidence of synthetic authorship than isolated hits.

Over-Commented Block1054 hits · 976 pts
SeverityFileLineSnippetContext
LOWNOTICE.txt41// Copyright (c) Microsoft Corporation. All rights reserved.COMMENT
LOWNOTICE.txt81* about the suitability of this software for any purpose.COMMENT
LOWNOTICE.txt101// days of receipt.COMMENT
LOWNOTICE.txt121// warranties of any kind are expressed or implied. The recipientCOMMENT
LOWNOTICE.txt141----------------------COMMENT
LOWNOTICE.txt161// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTIONCOMMENT
LOWNOTICE.txt181// YOU UNEQUIVOCALLY ACCEPT, AND AGREE TO BE BOUND BY, ALL OF THECOMMENT
LOWNOTICE.txt201// (b) this copyright and permission notice appear in associatedCOMMENT
LOWtools/validate/validate.cpp1// Copyright (c) Microsoft Corporation.COMMENT
LOWtools/scripts/charconv_tables_generate.cpp1// Copyright (c) Microsoft Corporation.COMMENT
LOW…nicode_properties_parse/unicode_properties_data_gen.py101// UNICODE, INC. LICENSE AGREEMENT - DATA FILES AND SOFTWARECOMMENT
LOW…nicode_properties_parse/unicode_properties_data_gen.py121// (the "Data Files") or Unicode software and any associated documentationCOMMENT
LOW…nicode_properties_parse/unicode_properties_data_gen.py141// PERFORMANCE OF THE DATA FILES OR SOFTWARE.COMMENT
LOW…nicode_properties_parse/unicode_properties_data_gen.py201// __printable_property_data comes from ucd/extracted/DerivedGeneralCategory.txt.COMMENT
LOWtests/libcxx/magic_comments.txt1// REQUIRES: c++03COMMENT
LOWtests/tr1/expected_results.txt1# Copyright (c) Microsoft Corporation.COMMENT
LOWtests/tr1/include/tdefs.h1// Copyright (c) Microsoft Corporation.COMMENT
LOWtests/tr1/include/tdefs.h21// Define the following macros on the command line:COMMENT
LOWtests/tr1/include/tdefs.h41#define CSTD ::COMMENT
LOWtests/tr1/include/tdefs.h61#define CHECK_STR(left, right) check_str(#left " == " #right, __FILE__, __LINE__, left, right)COMMENT
LOWtests/tr1/include/tdefs.h321typedef double _Complex Dbl_complex;COMMENT
LOWtests/tr1/include/tdefs.h341#endif // EPS_ULPFCOMMENT
LOWtests/tr1/include/tcvt.h1// Copyright (c) Microsoft Corporation.COMMENT
LOWtests/tr1/include/tcvt.h21int leave_chk(const char* fname) { // display message and quitCOMMENT
LOWtests/tr1/include/tspec_random.h1// Copyright (c) Microsoft Corporation.COMMENT
LOWtests/tr1/tests/string1/test.cpp1// Copyright (c) Microsoft Corporation.COMMENT
LOWtests/tr1/tests/cstdint/test.cpp1// Copyright (c) Microsoft Corporation.COMMENT
LOWtests/tr1/tests/cstdint/test.cpp21#define INT_LEAST32_MAX 0x7fffffffCOMMENT
LOWtests/tr1/tests/complex1/test.cpp1// Copyright (c) Microsoft Corporation.COMMENT
LOWtests/tr1/tests/memory/test.cpp1// Copyright (c) Microsoft Corporation.COMMENT
LOWtests/tr1/tests/regex2/test.cpp1// Copyright (c) Microsoft Corporation.COMMENT
LOWtests/tr1/tests/regex2/test.cpp21#define ALL (ECMA | BASIC | EXTENDED | AWK | GREP | EGREP)COMMENT
LOWtests/tr1/tests/locale1/test.cpp1// Copyright (c) Microsoft Corporation.COMMENT
LOWtests/tr1/tests/cctype/test.cpp1// Copyright (c) Microsoft Corporation.COMMENT
LOWtests/tr1/tests/cctype/test.cpp21 CHECK(STDx isalpha((int) 'a') != 0);COMMENT
LOWtests/tr1/tests/cctype/test.cpp41 CHECK(STDx isalnum((int) 'a') != 0);COMMENT
LOWtests/tr1/tests/cctype/test.cpp61 CHECK(STDx isdigit((int) 'a') == 0);COMMENT
LOWtests/tr1/tests/cctype/test.cpp81 CHECK(STDx islower((int) 'a') != 0);COMMENT
LOWtests/tr1/tests/cctype/test.cpp101 CHECK(STDx ispunct((int) 'a') == 0);COMMENT
LOWtests/tr1/tests/cstdbool/test.cpp1// Copyright (c) Microsoft Corporation.COMMENT
LOWtests/tr1/tests/cstdbool/test.cpp21#undef OKCOMMENT
LOWtests/tr1/tests/regex4/test.cpp1// Copyright (c) Microsoft Corporation.COMMENT
LOWtests/tr1/tests/locale7/test.cpp1// Copyright (c) Microsoft Corporation.COMMENT
LOWtests/tr1/tests/regex3/test.cpp1// Copyright (c) Microsoft Corporation.COMMENT
LOWtests/tr1/tests/cerrno/test.cpp1// Copyright (c) Microsoft Corporation.COMMENT
LOWtests/tr1/tests/functional9/test.cpp1// Copyright (c) Microsoft Corporation.COMMENT
LOWtests/tr1/tests/functional7/test.cpp1// Copyright (c) Microsoft Corporation.COMMENT
LOWtests/tr1/tests/algorithm/test.cpp1// Copyright (c) Microsoft Corporation.COMMENT
LOWtests/tr1/tests/type_traits5/test.cpp1// Copyright (c) Microsoft Corporation.COMMENT
LOWtests/tr1/tests/functional1/test.cpp1// Copyright (c) Microsoft Corporation.COMMENT
LOWtests/tr1/tests/functional6/test.cpp1// Copyright (c) Microsoft Corporation.COMMENT
LOWtests/tr1/tests/cwchar2/test.cpp1// Copyright (c) Microsoft Corporation.COMMENT
LOWtests/tr1/tests/atomic/test.cpp1// Copyright (c) Microsoft Corporation.COMMENT
LOWtests/tr1/tests/ios/test.cpp1// Copyright (c) Microsoft Corporation.COMMENT
LOWtests/tr1/tests/memory1/test.cpp1// Copyright (c) Microsoft Corporation.COMMENT
LOWtests/tr1/tests/iterator/test.cpp1// Copyright (c) Microsoft Corporation.COMMENT
LOWtests/tr1/tests/cstdio/test.cpp1// Copyright (c) Microsoft Corporation.COMMENT
LOWtests/tr1/tests/regex1/test.cpp1// Copyright (c) Microsoft Corporation.COMMENT
LOWtests/tr1/tests/locale2/test.cpp1// Copyright (c) Microsoft Corporation.COMMENT
LOWtests/tr1/tests/complex2/test.cpp1// Copyright (c) Microsoft Corporation.COMMENT
994 more matches not shown…
Verbosity Indicators10 hits · 18 pts
SeverityFileLineSnippetContext
LOWstl/inc/xcharconv_ryu.h1023 // Step 2: Determine the interval of valid decimal representations.COMMENT
LOWstl/inc/xcharconv_ryu.h1030 // Step 3: Convert to a decimal power base using 64-bit arithmetic.COMMENT
LOWstl/inc/xcharconv_ryu.h1723 // Step 2: Determine the interval of valid decimal representations.COMMENT
LOWstl/inc/xcharconv_ryu.h1731 // Step 3: Convert to a decimal power base using 128-bit arithmetic.COMMENT
LOWstl/inc/xcharconv_ryu.h1092 // Step 4: Find the shortest decimal representation in the interval of valid representations.COMMENT
LOWstl/inc/xcharconv_ryu.h1276 // Step 5: Print the decimal representation.COMMENT
LOWstl/inc/xcharconv_ryu.h1526 // Step 1: Decode the floating-point number, and unify normalized and subnormal cases.COMMENT
LOWstl/inc/xcharconv_ryu.h1790 // Step 4: Find the shortest decimal representation in the interval of valid representations.COMMENT
LOWstl/inc/xcharconv_ryu.h1884 // Step 5: Print the decimal representation.COMMENT
LOWstl/inc/xcharconv_ryu.h2234 // Step 1: Decode the floating-point number, and unify normalized and subnormal cases.COMMENT
Structural Annotation Overuse10 hits · 18 pts
SeverityFileLineSnippetContext
LOWstl/inc/xcharconv_ryu.h1023 // Step 2: Determine the interval of valid decimal representations.COMMENT
LOWstl/inc/xcharconv_ryu.h1030 // Step 3: Convert to a decimal power base using 64-bit arithmetic.COMMENT
LOWstl/inc/xcharconv_ryu.h1723 // Step 2: Determine the interval of valid decimal representations.COMMENT
LOWstl/inc/xcharconv_ryu.h1731 // Step 3: Convert to a decimal power base using 128-bit arithmetic.COMMENT
LOWstl/inc/xcharconv_ryu.h1092 // Step 4: Find the shortest decimal representation in the interval of valid representations.COMMENT
LOWstl/inc/xcharconv_ryu.h1276 // Step 5: Print the decimal representation.COMMENT
LOWstl/inc/xcharconv_ryu.h1526 // Step 1: Decode the floating-point number, and unify normalized and subnormal cases.COMMENT
LOWstl/inc/xcharconv_ryu.h1790 // Step 4: Find the shortest decimal representation in the interval of valid representations.COMMENT
LOWstl/inc/xcharconv_ryu.h1884 // Step 5: Print the decimal representation.COMMENT
LOWstl/inc/xcharconv_ryu.h2234 // Step 1: Decode the floating-point number, and unify normalized and subnormal cases.COMMENT
AI Slop Vocabulary4 hits · 10 pts
SeverityFileLineSnippetContext
MEDIUMtests/tr1/run.pl7# This file is part of a Microsoft-internal legacy test harness, which we hope to replace in the future.COMMENT
MEDIUMtests/std/run.pl7# This file is part of a Microsoft-internal legacy test harness, which we hope to replace in the future.COMMENT
MEDIUM…ts/std/tests/P0896R4_ranges_alg_inplace_merge/test.cpp61// Test GH-4863: <algorithm>: ranges::inplace_merge doesn't seem to be able to utilize ranges::upper_boundCOMMENT
LOWstl/inc/yvals_core.h712#if _HAS_CXX23 // TRANSITION, ABI, should just use [[no_unique_address]] when _HAS_CXX20.COMMENT
Deep Nesting10 hits · 10 pts
SeverityFileLineSnippetContext
LOW…icode_properties_parse/grapheme_break_test_data_gen.py24CODE
LOWtests/utils/stl/test/file_parsing.py115CODE
LOWtests/utils/stl/test/format.py51CODE
LOWtests/utils/stl/test/format.py78CODE
LOWtests/utils/stl/test/format.py210CODE
LOWtests/utils/stl/test/features.py24CODE
LOWtests/utils/stl/test/tests.py128CODE
LOWtests/utils/stl/test/tests.py175CODE
LOWtests/utils/stl/test/tests.py199CODE
LOWtests/utils/stl/test/tests.py278CODE
Self-Referential Comments2 hits · 6 pts
SeverityFileLineSnippetContext
MEDIUMtests/tr1/run.pl7# This file is part of a Microsoft-internal legacy test harness, which we hope to replace in the future.COMMENT
MEDIUMtests/std/run.pl7# This file is part of a Microsoft-internal legacy test harness, which we hope to replace in the future.COMMENT
Excessive Try-Catch Wrapping2 hits · 3 pts
SeverityFileLineSnippetContext
LOWtests/utils/stl/test/format.py244 except Exception as e:CODE
MEDIUMtests/utils/stl/test/format.py210def execute(self, test, litConfig):CODE
Fake / Example Data2 hits · 2 pts
SeverityFileLineSnippetContext
LOWbenchmarks/inc/lorem.hpp9 "Lorem ipsum dolor sit amet, consectetur adipiscing elit. Nullam mollis imperdiet massa, at dapibus elit interdum "CODE
LOWbenchmarks/inc/lorem.hpp9 "Lorem ipsum dolor sit amet, consectetur adipiscing elit. Nullam mollis imperdiet massa, at dapibus elit interdum "CODE
Hyper-Verbose Identifiers2 hits · 2 pts
SeverityFileLineSnippetContext
LOW…nicode_properties_parse/download_unicode_data_files.py32def download_unicode_data_files():CODE
LOW…nicode_properties_parse/unicode_properties_data_gen.py281def generate_width_estimate_intervals(filename: str, timestamp: str, width_2_ranges: list[PropertyRange]):STRING
Unused Imports1 hit · 1 pts
SeverityFileLineSnippetContext
LOWtests/utils/stl/test/params.py9CODE