A modern formatting library
This report presents the forensic synthetic code analysis of fmtlib/fmt, a C++ project with 23,653 GitHub stars. SynthScan v2.0 examined 55,711 lines of code across 69 source files, recording 482 pattern matches distributed across 10 syntactic categories. The overall adjusted score of 5.9 places this repository in the Low AI signal 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 482 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 | test/c-test.c | 1 | // Formatting library for C++ - the C API tests | COMMENT |
| LOW | test/posix-mock.h | 1 | // Formatting library for C++ - mocks of POSIX functions | COMMENT |
| LOW | test/mock-allocator.h | 1 | // Formatting library for C++ - mock allocator | COMMENT |
| LOW | test/util.h | 1 | // Formatting library for C++ - test utilities | COMMENT |
| LOW | test/test-assert.h | 1 | // Formatting library for C++ - test version of FMT_ASSERT | COMMENT |
| LOW | test/scan.h | 1 | // Formatting library for C++ - scanning API proof of concept | COMMENT |
| LOW | test/gtest-extra.h | 1 | // Formatting library for C++ - custom Google Test assertions | COMMENT |
| LOW | test/fuzzing/fuzzer-common.h | 1 | // Copyright (c) 2019, Paul Dreik | COMMENT |
| LOW | test/fuzzing/build.sh | 1 | #!/bin/sh | COMMENT |
| LOW | test/cuda-test/CMakeLists.txt | 1 | # We can find some usecases which follow the guide of CMake which uses | COMMENT |
| LOW | test/cuda-test/CMakeLists.txt | 21 | # providing another (non-CUDA) C++ source code. | COMMENT |
| LOW | test/gtest/gtest/gtest-spi.h | 1 | // Copyright 2007, Google Inc. | COMMENT |
| LOW | test/gtest/gtest/gtest-spi.h | 21 | // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT | COMMENT |
| LOW | test/gtest/gtest/gtest-spi.h | 121 | // A set of macros for testing Google Test assertions or code that's expected | COMMENT |
| LOW | test/gtest/gtest/gtest-spi.h | 181 | // being part of the failure message. | COMMENT |
| LOW | test/gtest/gtest/gtest.h | 1 | // Copyright 2005, Google Inc. | COMMENT |
| LOW | test/gtest/gtest/gtest.h | 21 | // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT | COMMENT |
| LOW | test/gtest/gtest/gtest.h | 41 | // | COMMENT |
| LOW | test/gtest/gtest/gtest.h | 61 | COMMENT | |
| LOW | test/gtest/gtest/gtest.h | 81 | // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR | COMMENT |
| LOW | test/gtest/gtest/gtest.h | 101 | // Copyright 2005, Google Inc. | COMMENT |
| LOW | test/gtest/gtest/gtest.h | 121 | // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT | COMMENT |
| LOW | test/gtest/gtest/gtest.h | 141 | // GOOGLETEST_CM0001 DO NOT DELETE | COMMENT |
| LOW | test/gtest/gtest/gtest.h | 161 | // provide a default definition. After this header is #included, all | COMMENT |
| LOW | test/gtest/gtest/gtest.h | 181 | // GTEST_HAS_STD_WSTRING - Define it to 1/0 to indicate that | COMMENT |
| LOW | test/gtest/gtest/gtest.h | 201 | // source version since 2008. The recommended value | COMMENT |
| LOW | test/gtest/gtest/gtest.h | 221 | // GTEST_OS_HPUX - HP-UX | COMMENT |
| LOW | test/gtest/gtest/gtest.h | 241 | // most stable support. Since core members of the Google Test project | COMMENT |
| LOW | test/gtest/gtest/gtest.h | 261 | // | COMMENT |
| LOW | test/gtest/gtest/gtest.h | 281 | // the given Google Test flag. | COMMENT |
| LOW | test/gtest/gtest/gtest.h | 301 | // is suppressed. | COMMENT |
| LOW | test/gtest/gtest/gtest.h | 321 | // Extended Regular Expression syntax on UNIX-like platforms | COMMENT |
| LOW | test/gtest/gtest/gtest.h | 341 | // BiggestInt - the biggest signed integer type. | COMMENT |
| LOW | test/gtest/gtest/gtest.h | 361 | #include <stdio.h> | COMMENT |
| LOW | test/gtest/gtest/gtest.h | 381 | #include <locale> | COMMENT |
| LOW | test/gtest/gtest/gtest.h | 401 | // contributors may be used to endorse or promote products derived from | COMMENT |
| LOW | test/gtest/gtest/gtest.h | 421 | #define GOOGLETEST_INCLUDE_GTEST_INTERNAL_CUSTOM_GTEST_PORT_H_ | COMMENT |
| LOW | test/gtest/gtest/gtest.h | 441 | // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS | COMMENT |
| LOW | test/gtest/gtest/gtest.h | 461 | // Determines the platform on which Google Test is compiled. | COMMENT |
| LOW | test/gtest/gtest/gtest.h | 481 | # define GTEST_OS_WINDOWS_TV_TITLE 1 | COMMENT |
| LOW | test/gtest/gtest/gtest.h | 501 | # define GTEST_OS_FREEBSD 1 | COMMENT |
| LOW | test/gtest/gtest/gtest.h | 521 | #elif defined __NetBSD__ | COMMENT |
| LOW | test/gtest/gtest/gtest.h | 541 | # define GTEST_FLAG_PREFIX_ "gtest_" | COMMENT |
| LOW | test/gtest/gtest/gtest.h | 561 | // GTEST_DISABLE_MSC_WARNINGS_PUSH_(4800 4385) | COMMENT |
| LOW | test/gtest/gtest/gtest.h | 581 | _Pragma("clang diagnostic ignored \"-Wdeprecated-declarations\"") \ | COMMENT |
| LOW | test/gtest/gtest/gtest.h | 601 | #if GTEST_OS_WINDOWS_MINGW && !defined(__MINGW64_VERSION_MAJOR) | COMMENT |
| LOW | test/gtest/gtest/gtest.h | 621 | #endif // GTEST_OS_WINDOWS | COMMENT |
| LOW | test/gtest/gtest/gtest.h | 641 | COMMENT | |
| LOW | test/gtest/gtest/gtest.h | 661 | // simple regex implementation instead. | COMMENT |
| LOW | test/gtest/gtest/gtest.h | 681 | // clang defines __EXCEPTIONS if and only if exceptions are enabled before clang | COMMENT |
| LOW | test/gtest/gtest/gtest.h | 701 | # elif defined(__HP_aCC) | COMMENT |
| LOW | test/gtest/gtest/gtest.h | 721 | COMMENT | |
| LOW | test/gtest/gtest/gtest.h | 741 | # ifdef __GXX_RTTI | COMMENT |
| LOW | test/gtest/gtest/gtest.h | 761 | # define GTEST_HAS_RTTI __has_feature(cxx_rtti) | COMMENT |
| LOW | test/gtest/gtest/gtest.h | 781 | COMMENT | |
| LOW | test/gtest/gtest/gtest.h | 801 | COMMENT | |
| LOW | test/gtest/gtest/gtest.h | 821 | // architecture. | COMMENT |
| LOW | test/gtest/gtest/gtest.h | 841 | #ifndef GTEST_HAS_STREAM_REDIRECTION | COMMENT |
| LOW | test/gtest/gtest/gtest.h | 861 | #endif | COMMENT |
| LOW | test/gtest/gtest/gtest.h | 881 | #endif | COMMENT |
| 392 more matches not shown… | ||||
| Severity | File | Line | Snippet | Context |
|---|---|---|---|---|
| MEDIUM | test/gtest/gtest/gtest.h | 7407 | // This implementation is *not* meant to be as highly tuned or robust | COMMENT |
| MEDIUM | test/gtest/gtest/gtest.h | 7478 | // In practice, this can be used to test functions that utilize the | COMMENT |
| MEDIUM | include/fmt/format.h | 3386 | // Compilers are not aware of how to leverage the maximum value of | COMMENT |
| Severity | File | Line | Snippet | Context |
|---|---|---|---|---|
| LOW | support/docopt.py | 72 | CODE | |
| LOW | support/docopt.py | 301 | CODE | |
| LOW | support/docopt.py | 334 | CODE | |
| LOW | support/docopt.py | 402 | CODE | |
| LOW | support/docopt.py | 428 | CODE | |
| LOW | support/docopt.py | 57 | CODE | |
| LOW | support/printable.py | 133 | CODE | |
| LOW | support/python/mkdocstrings_handlers/cxx/__init__.py | 358 | CODE |
| Severity | File | Line | Snippet | Context |
|---|---|---|---|---|
| HIGH | support/release.py | 200 | fmt_repo.push('origin', 'release') | CODE |
| HIGH | support/printable.py | 194 | print(" if (0x{:x} <= cp && cp < 0x{:x}) return false;".format(a, a + b)) | STRING |
| Severity | File | Line | Snippet | Context |
|---|---|---|---|---|
| LOW | support/release.py | 12 | CODE | |
| LOW | support/release.py | 13 | CODE | |
| LOW | support/python/mkdocstrings_handlers/cxx/__init__.py | 17 | CODE | |
| LOW | support/python/mkdocstrings_handlers/cxx/__init__.py | 17 | CODE | |
| LOW | support/python/mkdocstrings_handlers/cxx/__init__.py | 19 | CODE | |
| LOW | support/python/mkdocstrings_handlers/cxx/__init__.py | 20 | CODE | |
| LOW | support/python/mkdocstrings_handlers/cxx/__init__.py | 20 | CODE |
| Severity | File | Line | Snippet | Context |
|---|---|---|---|---|
| LOW | include/fmt/format-inl.h | 1275 | // Step 1: integer promotion & Schubfach multiplier calculation. | COMMENT |
| LOW | include/fmt/format-inl.h | 1330 | // Step 2: Try larger divisor; remove trailing zeros if necessary. | COMMENT |
| LOW | include/fmt/format-inl.h | 1362 | // Step 3: Find the significand with the smaller divisor. | COMMENT |
| Severity | File | Line | Snippet | Context |
|---|---|---|---|---|
| LOW | include/fmt/format-inl.h | 1275 | // Step 1: integer promotion & Schubfach multiplier calculation. | COMMENT |
| LOW | include/fmt/format-inl.h | 1330 | // Step 2: Try larger divisor; remove trailing zeros if necessary. | COMMENT |
| LOW | include/fmt/format-inl.h | 1362 | // Step 3: Find the significand with the smaller divisor. | COMMENT |
| Severity | File | Line | Snippet | Context |
|---|---|---|---|---|
| MEDIUM | doc/ChangeLog-old.md | 2026 | fmt::print("Error: "); | CODE |
| MEDIUM | doc/ChangeLog-old.md | 3171 | fmt::print("Error: {}"); | CODE |
| Severity | File | Line | Snippet | Context |
|---|---|---|---|---|
| MEDIUM | support/release.py | 196 | # Create a draft release on GitHub, then trigger the release workflow to | COMMENT |
| Severity | File | Line | Snippet | Context |
|---|---|---|---|---|
| LOW | support/docopt.py | 13 | __all__ = ['docopt'] | CODE |