MSVC's implementation of the C++ Standard Library.
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).
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.
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.
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.
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.
| Severity | File | Line | Snippet | Context |
|---|---|---|---|---|
| LOW | NOTICE.txt | 41 | // Copyright (c) Microsoft Corporation. All rights reserved. | COMMENT |
| LOW | NOTICE.txt | 81 | * about the suitability of this software for any purpose. | COMMENT |
| LOW | NOTICE.txt | 101 | // days of receipt. | COMMENT |
| LOW | NOTICE.txt | 121 | // warranties of any kind are expressed or implied. The recipient | COMMENT |
| LOW | NOTICE.txt | 141 | ---------------------- | COMMENT |
| LOW | NOTICE.txt | 161 | // OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION | COMMENT |
| LOW | NOTICE.txt | 181 | // YOU UNEQUIVOCALLY ACCEPT, AND AGREE TO BE BOUND BY, ALL OF THE | COMMENT |
| LOW | NOTICE.txt | 201 | // (b) this copyright and permission notice appear in associated | COMMENT |
| LOW | tools/validate/validate.cpp | 1 | // Copyright (c) Microsoft Corporation. | COMMENT |
| LOW | tools/scripts/charconv_tables_generate.cpp | 1 | // Copyright (c) Microsoft Corporation. | COMMENT |
| LOW | …nicode_properties_parse/unicode_properties_data_gen.py | 101 | // UNICODE, INC. LICENSE AGREEMENT - DATA FILES AND SOFTWARE | COMMENT |
| LOW | …nicode_properties_parse/unicode_properties_data_gen.py | 121 | // (the "Data Files") or Unicode software and any associated documentation | COMMENT |
| LOW | …nicode_properties_parse/unicode_properties_data_gen.py | 141 | // PERFORMANCE OF THE DATA FILES OR SOFTWARE. | COMMENT |
| LOW | …nicode_properties_parse/unicode_properties_data_gen.py | 201 | // __printable_property_data comes from ucd/extracted/DerivedGeneralCategory.txt. | COMMENT |
| LOW | tests/libcxx/magic_comments.txt | 1 | // REQUIRES: c++03 | COMMENT |
| LOW | tests/tr1/expected_results.txt | 1 | # Copyright (c) Microsoft Corporation. | COMMENT |
| LOW | tests/tr1/include/tdefs.h | 1 | // Copyright (c) Microsoft Corporation. | COMMENT |
| LOW | tests/tr1/include/tdefs.h | 21 | // Define the following macros on the command line: | COMMENT |
| LOW | tests/tr1/include/tdefs.h | 41 | #define CSTD :: | COMMENT |
| LOW | tests/tr1/include/tdefs.h | 61 | #define CHECK_STR(left, right) check_str(#left " == " #right, __FILE__, __LINE__, left, right) | COMMENT |
| LOW | tests/tr1/include/tdefs.h | 321 | typedef double _Complex Dbl_complex; | COMMENT |
| LOW | tests/tr1/include/tdefs.h | 341 | #endif // EPS_ULPF | COMMENT |
| LOW | tests/tr1/include/tcvt.h | 1 | // Copyright (c) Microsoft Corporation. | COMMENT |
| LOW | tests/tr1/include/tcvt.h | 21 | int leave_chk(const char* fname) { // display message and quit | COMMENT |
| LOW | tests/tr1/include/tspec_random.h | 1 | // Copyright (c) Microsoft Corporation. | COMMENT |
| LOW | tests/tr1/tests/string1/test.cpp | 1 | // Copyright (c) Microsoft Corporation. | COMMENT |
| LOW | tests/tr1/tests/cstdint/test.cpp | 1 | // Copyright (c) Microsoft Corporation. | COMMENT |
| LOW | tests/tr1/tests/cstdint/test.cpp | 21 | #define INT_LEAST32_MAX 0x7fffffff | COMMENT |
| LOW | tests/tr1/tests/complex1/test.cpp | 1 | // Copyright (c) Microsoft Corporation. | COMMENT |
| LOW | tests/tr1/tests/memory/test.cpp | 1 | // Copyright (c) Microsoft Corporation. | COMMENT |
| LOW | tests/tr1/tests/regex2/test.cpp | 1 | // Copyright (c) Microsoft Corporation. | COMMENT |
| LOW | tests/tr1/tests/regex2/test.cpp | 21 | #define ALL (ECMA | BASIC | EXTENDED | AWK | GREP | EGREP) | COMMENT |
| LOW | tests/tr1/tests/locale1/test.cpp | 1 | // Copyright (c) Microsoft Corporation. | COMMENT |
| LOW | tests/tr1/tests/cctype/test.cpp | 1 | // Copyright (c) Microsoft Corporation. | COMMENT |
| LOW | tests/tr1/tests/cctype/test.cpp | 21 | CHECK(STDx isalpha((int) 'a') != 0); | COMMENT |
| LOW | tests/tr1/tests/cctype/test.cpp | 41 | CHECK(STDx isalnum((int) 'a') != 0); | COMMENT |
| LOW | tests/tr1/tests/cctype/test.cpp | 61 | CHECK(STDx isdigit((int) 'a') == 0); | COMMENT |
| LOW | tests/tr1/tests/cctype/test.cpp | 81 | CHECK(STDx islower((int) 'a') != 0); | COMMENT |
| LOW | tests/tr1/tests/cctype/test.cpp | 101 | CHECK(STDx ispunct((int) 'a') == 0); | COMMENT |
| LOW | tests/tr1/tests/cstdbool/test.cpp | 1 | // Copyright (c) Microsoft Corporation. | COMMENT |
| LOW | tests/tr1/tests/cstdbool/test.cpp | 21 | #undef OK | COMMENT |
| LOW | tests/tr1/tests/regex4/test.cpp | 1 | // Copyright (c) Microsoft Corporation. | COMMENT |
| LOW | tests/tr1/tests/locale7/test.cpp | 1 | // Copyright (c) Microsoft Corporation. | COMMENT |
| LOW | tests/tr1/tests/regex3/test.cpp | 1 | // Copyright (c) Microsoft Corporation. | COMMENT |
| LOW | tests/tr1/tests/cerrno/test.cpp | 1 | // Copyright (c) Microsoft Corporation. | COMMENT |
| LOW | tests/tr1/tests/functional9/test.cpp | 1 | // Copyright (c) Microsoft Corporation. | COMMENT |
| LOW | tests/tr1/tests/functional7/test.cpp | 1 | // Copyright (c) Microsoft Corporation. | COMMENT |
| LOW | tests/tr1/tests/algorithm/test.cpp | 1 | // Copyright (c) Microsoft Corporation. | COMMENT |
| LOW | tests/tr1/tests/type_traits5/test.cpp | 1 | // Copyright (c) Microsoft Corporation. | COMMENT |
| LOW | tests/tr1/tests/functional1/test.cpp | 1 | // Copyright (c) Microsoft Corporation. | COMMENT |
| LOW | tests/tr1/tests/functional6/test.cpp | 1 | // Copyright (c) Microsoft Corporation. | COMMENT |
| LOW | tests/tr1/tests/cwchar2/test.cpp | 1 | // Copyright (c) Microsoft Corporation. | COMMENT |
| LOW | tests/tr1/tests/atomic/test.cpp | 1 | // Copyright (c) Microsoft Corporation. | COMMENT |
| LOW | tests/tr1/tests/ios/test.cpp | 1 | // Copyright (c) Microsoft Corporation. | COMMENT |
| LOW | tests/tr1/tests/memory1/test.cpp | 1 | // Copyright (c) Microsoft Corporation. | COMMENT |
| LOW | tests/tr1/tests/iterator/test.cpp | 1 | // Copyright (c) Microsoft Corporation. | COMMENT |
| LOW | tests/tr1/tests/cstdio/test.cpp | 1 | // Copyright (c) Microsoft Corporation. | COMMENT |
| LOW | tests/tr1/tests/regex1/test.cpp | 1 | // Copyright (c) Microsoft Corporation. | COMMENT |
| LOW | tests/tr1/tests/locale2/test.cpp | 1 | // Copyright (c) Microsoft Corporation. | COMMENT |
| LOW | tests/tr1/tests/complex2/test.cpp | 1 | // Copyright (c) Microsoft Corporation. | COMMENT |
| 994 more matches not shown… | ||||
| Severity | File | Line | Snippet | Context |
|---|---|---|---|---|
| LOW⚡ | stl/inc/xcharconv_ryu.h | 1023 | // Step 2: Determine the interval of valid decimal representations. | COMMENT |
| LOW⚡ | stl/inc/xcharconv_ryu.h | 1030 | // Step 3: Convert to a decimal power base using 64-bit arithmetic. | COMMENT |
| LOW⚡ | stl/inc/xcharconv_ryu.h | 1723 | // Step 2: Determine the interval of valid decimal representations. | COMMENT |
| LOW⚡ | stl/inc/xcharconv_ryu.h | 1731 | // Step 3: Convert to a decimal power base using 128-bit arithmetic. | COMMENT |
| LOW | stl/inc/xcharconv_ryu.h | 1092 | // Step 4: Find the shortest decimal representation in the interval of valid representations. | COMMENT |
| LOW | stl/inc/xcharconv_ryu.h | 1276 | // Step 5: Print the decimal representation. | COMMENT |
| LOW | stl/inc/xcharconv_ryu.h | 1526 | // Step 1: Decode the floating-point number, and unify normalized and subnormal cases. | COMMENT |
| LOW | stl/inc/xcharconv_ryu.h | 1790 | // Step 4: Find the shortest decimal representation in the interval of valid representations. | COMMENT |
| LOW | stl/inc/xcharconv_ryu.h | 1884 | // Step 5: Print the decimal representation. | COMMENT |
| LOW | stl/inc/xcharconv_ryu.h | 2234 | // Step 1: Decode the floating-point number, and unify normalized and subnormal cases. | COMMENT |
| Severity | File | Line | Snippet | Context |
|---|---|---|---|---|
| LOW⚡ | stl/inc/xcharconv_ryu.h | 1023 | // Step 2: Determine the interval of valid decimal representations. | COMMENT |
| LOW⚡ | stl/inc/xcharconv_ryu.h | 1030 | // Step 3: Convert to a decimal power base using 64-bit arithmetic. | COMMENT |
| LOW⚡ | stl/inc/xcharconv_ryu.h | 1723 | // Step 2: Determine the interval of valid decimal representations. | COMMENT |
| LOW⚡ | stl/inc/xcharconv_ryu.h | 1731 | // Step 3: Convert to a decimal power base using 128-bit arithmetic. | COMMENT |
| LOW | stl/inc/xcharconv_ryu.h | 1092 | // Step 4: Find the shortest decimal representation in the interval of valid representations. | COMMENT |
| LOW | stl/inc/xcharconv_ryu.h | 1276 | // Step 5: Print the decimal representation. | COMMENT |
| LOW | stl/inc/xcharconv_ryu.h | 1526 | // Step 1: Decode the floating-point number, and unify normalized and subnormal cases. | COMMENT |
| LOW | stl/inc/xcharconv_ryu.h | 1790 | // Step 4: Find the shortest decimal representation in the interval of valid representations. | COMMENT |
| LOW | stl/inc/xcharconv_ryu.h | 1884 | // Step 5: Print the decimal representation. | COMMENT |
| LOW | stl/inc/xcharconv_ryu.h | 2234 | // Step 1: Decode the floating-point number, and unify normalized and subnormal cases. | COMMENT |
| Severity | File | Line | Snippet | Context |
|---|---|---|---|---|
| MEDIUM | tests/tr1/run.pl | 7 | # This file is part of a Microsoft-internal legacy test harness, which we hope to replace in the future. | COMMENT |
| MEDIUM | tests/std/run.pl | 7 | # 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.cpp | 61 | // Test GH-4863: <algorithm>: ranges::inplace_merge doesn't seem to be able to utilize ranges::upper_bound | COMMENT |
| LOW | stl/inc/yvals_core.h | 712 | #if _HAS_CXX23 // TRANSITION, ABI, should just use [[no_unique_address]] when _HAS_CXX20. | COMMENT |
| Severity | File | Line | Snippet | Context |
|---|---|---|---|---|
| LOW | …icode_properties_parse/grapheme_break_test_data_gen.py | 24 | CODE | |
| LOW | tests/utils/stl/test/file_parsing.py | 115 | CODE | |
| LOW | tests/utils/stl/test/format.py | 51 | CODE | |
| LOW | tests/utils/stl/test/format.py | 78 | CODE | |
| LOW | tests/utils/stl/test/format.py | 210 | CODE | |
| LOW | tests/utils/stl/test/features.py | 24 | CODE | |
| LOW | tests/utils/stl/test/tests.py | 128 | CODE | |
| LOW | tests/utils/stl/test/tests.py | 175 | CODE | |
| LOW | tests/utils/stl/test/tests.py | 199 | CODE | |
| LOW | tests/utils/stl/test/tests.py | 278 | CODE |
| Severity | File | Line | Snippet | Context |
|---|---|---|---|---|
| MEDIUM | tests/tr1/run.pl | 7 | # This file is part of a Microsoft-internal legacy test harness, which we hope to replace in the future. | COMMENT |
| MEDIUM | tests/std/run.pl | 7 | # This file is part of a Microsoft-internal legacy test harness, which we hope to replace in the future. | COMMENT |
| Severity | File | Line | Snippet | Context |
|---|---|---|---|---|
| LOW | tests/utils/stl/test/format.py | 244 | except Exception as e: | CODE |
| MEDIUM | tests/utils/stl/test/format.py | 210 | def execute(self, test, litConfig): | CODE |
| Severity | File | Line | Snippet | Context |
|---|---|---|---|---|
| LOW | benchmarks/inc/lorem.hpp | 9 | "Lorem ipsum dolor sit amet, consectetur adipiscing elit. Nullam mollis imperdiet massa, at dapibus elit interdum " | CODE |
| LOW | benchmarks/inc/lorem.hpp | 9 | "Lorem ipsum dolor sit amet, consectetur adipiscing elit. Nullam mollis imperdiet massa, at dapibus elit interdum " | CODE |
| Severity | File | Line | Snippet | Context |
|---|---|---|---|---|
| LOW | …nicode_properties_parse/download_unicode_data_files.py | 32 | def download_unicode_data_files(): | CODE |
| LOW | …nicode_properties_parse/unicode_properties_data_gen.py | 281 | def generate_width_estimate_intervals(filename: str, timestamp: str, width_2_ranges: list[PropertyRange]): | STRING |
| Severity | File | Line | Snippet | Context |
|---|---|---|---|---|
| LOW | tests/utils/stl/test/params.py | 9 | CODE |