Fuzz introspector
For issues and ideas: https://github.com/ossf/fuzz-introspector/issues
Project coverage

Table of contents

Project overview: cffi
High level conclusions
Reachability and coverage overview
Fuzzers overview
Project functions overview
Fuzzer details
Fuzzer: fuzz_recompiler
Call tree
Fuzz blockers
Runtime coverage analysis
Files reached
Analyses and suggestions
Optimal target analysis
Remaining optimal interesting functions
All functions overview
Fuzz engine guidance
/src/fuzz_recompiler.py
Dictionary
Fuzzer function priority
Runtime coverage analysis
Complex functions with low coverage
Files and Directories in report
Files in report
Directories in report
Metadata section
Report generation date: 2025-08-29

Project overview: cffi

High level conclusions

Reachability and coverage overview

Functions statically reachable by fuzzers
17.0%
90 / 540
Cyclomatic complexity statically reachable by fuzzers
19.0%
366 / 1896
Runtime code coverage of functions
24.0%
127 / 540

Warning: The number of runtime covered functions are larger than the number of reachable functions. This means that Fuzz Introspector found there are more functions covered at runtime than what is considered reachable based on the static analysis. This is a limitation in the analysis as anything covered at runtime is by definition reachable by the fuzzers.
This is likely due to a limitation in the static analysis. In this case, the count of functions covered at runtime is the true value, which means this is what should be considered "achieved" by the fuzzer.

Use the project functions table below to query all functions that were not covered at runtime.

Fuzzers overview

Fuzzer Fuzzer filename Functions Reached Functions unreached Fuzzer depth Files reached Basic blocks reached Cyclomatic complexity Details
fuzz_recompiler /src/fuzz_recompiler.py 234 782 16 7 255 796 fuzz_recompiler.py

Project functions overview

The following table shows data about each function in the project. The functions included in this table correspond to all functions that exist in the executables of the fuzzers. As such, there may be functions that are from third-party libraries.

For further technical details on the meaning of columns in the below table, please see the Glossary .

Func name Functions filename Args Function call depth Reached by Fuzzers Runtime reached by Fuzzers Combined reached by Fuzzers Fuzzers runtime hit Func lines hit % I Count BB Count Cyclomatic complexity Functions reached Reached by functions Accumulated cyclomatic complexity Undiscovered complexity

Fuzzer details

Fuzzer: fuzz_recompiler

Call tree

The calltree shows the control flow of the fuzzer. This is overlaid with coverage information to display how much of the potential code a fuzzer can reach is in fact covered at runtime. In the following there is a link to a detailed calltree visualisation as well as a bitmap showing a high-level view of the calltree. For further information about these topics please see the glossary for full calltree and calltree overview

Full calltree

Call tree overview bitmap:

The distribution of callsites in terms of coloring is
Color Runtime hitcount Callsite count Percentage
red 0 175 34.1%
gold [1:9] 0 0.0%
yellow [10:29] 0 0.0%
greenyellow [30:49] 0 0.0%
lawngreen 50+ 337 65.8%
All colors 512 100

Fuzz blockers

The following nodes represent call sites where fuzz blockers occur.

Amount of callsites blocked Calltree index Parent function Callsite Largest blocked function
23 306 cffi.model.PointerType.build_backend_type call site: 00306 cffi.model.BaseTypeByIdentity.get_cached_btype
22 32 cffi.model.BaseTypeByIdentity.get_cached_btype call site: 00032 cffi.model.EnumType.build_baseinttype
12 62 cffi.cparser._preprocess call site: 00062 cffi.cparser._workaround_for_old_pycparser
12 79 cffi.cparser._preprocess_extern_python call site: 00079 match.end
12 221 cffi.model.StructOrUnion.__init__ call site: 00221 cffi.cparser.Parser._build_enum_type
8 289 cffi.cparser.Parser._get_type_and_quals call site: 00289 cffi.api.FFI._get_cached_btype
6 406 cffi.cparser.Parser._parse_decl call site: 00406 cffi.cparser.Parser._add_integer_constant
5 14 cffi.model.get_typecache call site: 00014 .type
4 166 cffi.cparser.Parser._parse_constant call site: 00166 .int
4 238 cffi.cparser.Parser._get_struct_union_enum_type call site: 00238 cffi.model.EnumType.force_the_name
4 263 cffi.cparser.Parser._get_struct_union_enum_type call site: 00263 cffi.cparser.Parser._get_struct_union_enum_type
4 335 cffi.model.BaseTypeByIdentity.get_cached_btype call site: 00335 cffi.model.global_cache

Runtime coverage analysis

Covered functions
147
Functions that are reachable but not covered
156
Reachable functions
234
Percentage of reachable functions covered
33.33%
NB: The sum of covered functions and functions that are reachable but not covered need not be equal to Reachable functions . This is because the reachability analysis is an approximation and thus at runtime some functions may be covered that are not included in the reachability analysis. This is a limitation of our static analysis capabilities.
Function name source code lines source lines hit percentage hit

Files reached

filename functions hit
/ 1
...fuzz_recompiler 7
cffi.api 36
cffi.cparser 126
cffi.model 65
cffi.commontypes 4
cffi.recompiler 30

Analyses and suggestions

Optimal target analysis

Remaining optimal interesting functions

The following table shows a list of functions that are optimal targets. Optimal targets are identified by finding the functions that in combination, yield a high code coverage.

Func name Functions filename Arg count Args Function depth hitcount instr count bb count cyclomatic complexity Reachable functions Incoming references total cyclomatic complexity Unreached complexity
cffi.api.FFI.distutils_extension cffi.api 3 ['N/A', 'N/A', 'N/A'] 5 0 3 5 5 143 0 474 320
cffi.recompiler.Recompiler._generate_cpy_function_decl cffi.recompiler 3 ['N/A', 'N/A', 'N/A'] 4 0 51 14 9 40 0 141 75
cffi.verifier.Verifier.__init__ cffi.verifier 12 ['N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A', 'N/A'] 3 0 1 5 5 28 1 96 72
cffi.setuptools_ext.add_cffi_module cffi.setuptools_ext 2 ['N/A', 'N/A'] 3 0 10 8 6 26 1 85 55
cffi.vengine_gen.VGenericEngine._loaded_gen_function cffi.vengine_gen 5 ['N/A', 'N/A', 'N/A', 'N/A', 'N/A'] 26 0 6 5 5 181 0 614 44
cffi.vengine_cpy.VCPythonEngine._generate_cpy_function_decl cffi.vengine_cpy 3 ['N/A', 'N/A', 'N/A'] 4 0 32 7 6 28 0 98 43
cffi.vengine_cpy.VCPythonEngine.load_library cffi.vengine_cpy 2 ['N/A', 'N/A'] 3 0 7 4 5 27 0 86 38

Implementing fuzzers that target the above functions will improve reachability such that it becomes:

Functions statically reachable by fuzzers
30.0%
161 / 540
Cyclomatic complexity statically reachable by fuzzers
34.0%
648 / 1896

All functions overview

If you implement fuzzers for these functions, the status of all functions in the project will be:

Func name Functions filename Args Function call depth Reached by Fuzzers Runtime reached by Fuzzers Combined reached by Fuzzers Fuzzers runtime hit Func lines hit % I Count BB Count Cyclomatic complexity Functions reached Reached by functions Accumulated cyclomatic complexity Undiscovered complexity

Fuzz engine guidance

This sections provides heuristics that can be used as input to a fuzz engine when running a given fuzz target. The current focus is on providing input that is usable by libFuzzer.

/src/fuzz_recompiler.py

Dictionary

Use this with the libFuzzer -dict=DICT.file flag


Fuzzer function priority

Use one of these functions as input to libfuzzer with flag: -focus_function name 

-focus_function=['cffi.model.PointerType.build_backend_type', 'cffi.model.BaseTypeByIdentity.get_cached_btype', 'cffi.cparser._preprocess', 'cffi.cparser._preprocess_extern_python', 'cffi.model.StructOrUnion.__init__', 'cffi.cparser.Parser._get_type_and_quals', 'cffi.cparser.Parser._parse_decl', 'cffi.model.get_typecache', 'cffi.cparser.Parser._parse_constant', 'cffi.cparser.Parser._get_struct_union_enum_type']

Runtime coverage analysis

This section shows analysis of runtime coverage data.

For futher technical details on how this section is generated, please see the Glossary .

Complex functions with low coverage

Func name Function total lines Lines covered at runtime percentage covered Reached by fuzzers
cffi.api.FFI._apply_embedding_fix.ensure 33 0 0.0% []
cffi.recompiler.Recompiler.write_c_source_to_f 133 0 0.0% []
cffi.recompiler.Recompiler._generate_cpy_function_decl 87 0 0.0% []
cffi.recompiler.Recompiler._generate_cpy_function_decl.need_indirection 38 0 0.0% []
cffi.recompiler.recompile 45 0 0.0% []
cffi.cparser.Parser._parse_constant 53 29 54.71% ['fuzz_recompiler']
cffi.model.StructOrUnion.finish_backend_type 39 0 0.0% ['fuzz_recompiler']
x.split 694 287 41.35% ['fuzz_recompiler']

Files and Directories in report

This section shows which files and directories are considered in this report. The main reason for showing this is fuzz introspector may include more code in the reasoning than is desired. This section helps identify if too many files/directories are included, e.g. third party code, which may be irrelevant for the threat model. In the event too much is included, fuzz introspector supports a configuration file that can exclude data from the report. See the following link for more information on how to create a config file: link

Files in report

Source file Reached by Covered by
[] []
shutil [] []
warnings [] []
...fuzz_recompiler ['fuzz_recompiler'] []
atheris [] []
pycparser [] []
ctypes [] []
cffi.ffiplatform [] []
distutils [] []
_cffi_backend [] []
os [] []
subprocess [] []
_dummy_thread [] []
_thread [] []
sys [] []
re [] []
cffi.model ['fuzz_recompiler'] []
cffi [] []
cffi.error [] []
cffi.vengine_cpy [] []
cffi.commontypes ['fuzz_recompiler'] []
cffi.pkgconfig [] []
sysconfig [] []
cffi.api ['fuzz_recompiler'] []
dummy_thread [] []
_imp [] []
cffi.recompiler ['fuzz_recompiler'] []
importlib [] []
io [] []
thread [] []
cffi.cparser ['fuzz_recompiler'] []
weakref [] []
cffi.setuptools_ext [] []
cffi.verifier [] []
binascii [] []
cffi.lock [] []
types [] []
cffi.backend_ctypes [] []
[] []
cffi._imp_emulation [] []
traceback [] []
tokenize [] []
imp [] []
cffi.vengine_gen [] []
_pycparser [] []
setuptools [] []
cffi.cffi_opcode [] []

Directories in report

Directory

Metadata section

This sections shows the raw data that is used to produce this report. This is mainly used for further processing and developer debugging.

Fuzzer Calltree file Program data file Coverage file
fuzz_recompiler fuzzerLogFile-fuzz_recompiler.data fuzzerLogFile-fuzz_recompiler.data.yaml all_cov.json