Report generation date: 2025-07-11

Project overview: lark-parser

High level conclusions

The runtime code coverage of fuzz_parse covers 4.0% of its statically reachable code. This means there is some place that blocks the fuzzer to continue exploring more code at run time.

Reachability and coverage overview

Functions statically reachable by fuzzers

80 / 623

Cyclomatic complexity statically reachable by fuzzers

303 / 2072

Runtime code coverage of functions

45 / 623

Fuzzers overview

Fuzzer	Fuzzer filename	Functions Reached	Functions unreached	Fuzzer depth	Files reached	Basic blocks reached	Cyclomatic complexity	Details
fuzz_parse	/src/fuzz_parse.py	200	892	7	11	163	660	fuzz_parse.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_parse

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 0 321 85.1%

gold [1:9] 0 0.0%

yellow [10:29] 0 0.0%

greenyellow [30:49] 0 0.0%

lawngreen 50+ 56 14.8%

All colors 377 100

Color	Runtime hitcount	Callsite count	Percentage
red	0	321	85.1%
gold	[1:9]	0	0.0%
yellow	[10:29]	0	0.0%
greenyellow	[30:49]	0	0.0%
lawngreen	50+	56	14.8%
All colors	377	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
120	172	lark.visitors.Transformer_InPlace.transform	call site: 00172	lark.load_grammar.GrammarBuilder.do_import
38	14	lark.lark.Lark.__init__	call site: 00014	lark.lark.Lark._load
26	56	lark.utils._deserialize	call site: 00056	lark.lark.Lark._deserialize_lexer_conf
22	129	lark.lark.Lark.__init__	call site: 00129	lark.load_grammar.GrammarBuilder.load_grammar
15	317	lark.lexer.BasicLexer.__init__	call site: 00317	lark.lexer._check_regex_collisions
14	333	lark.lexer._check_regex_collisions	call site: 00333	lark.lark.Lark.save
12	116	lark.parser_frontends._wrap_lexer	call site: 00116	lark.parser_frontends.create_contextual_lexer
11	352	lark.utils.Serialize.memo_serialize	call site: 00352	lark.utils._serialize
8	306	lark.parser_frontends._construct_parsing_frontend	call site: 00306	lark.lark.Lark._build_lexer
7	83	lark.lark.Lark._prepare_callbacks	call site: 00083	lark.parse_tree_builder.ParseTreeBuilder._init_builders
7	162	lark.common.ParserConf.__init__	call site: 00162	lark.load_grammar._get_parser
6	370	lark.lark.Lark.parse	call site: 00370	lark.parser_frontends.ParsingFrontend._verify_start

Runtime coverage analysis

Covered functions

58

Functions that are reachable but not covered

192

Reachable functions

200

Percentage of reachable functions covered

4.0%

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_parse	5
lark.lark	47
lark.load_grammar	88
lark.utils	33
lark.parser_frontends	25
lark.parse_tree_builder	11
lark.lexer	20
lark.grammar	3
lark.common	2
lark.visitors	3

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	instr count	bb count	cyclomatic complexity	Reachable functions	Incoming references	total cyclomatic complexity	Unreached complexity
`lark.reconstruct.Reconstructor.reconstruct`	lark.reconstruct	4	['N/A', 'N/A', 'N/A', 'N/A']	8	2	2	4	109	0	354	258
`lark.load_grammar.Grammar.compile`	lark.load_grammar	3	['N/A', 'N/A', 'N/A']	5	5	12	8	66	0	209	116
`lark.parsers.lalr_parser.LALR_Parser.parse`	lark.parsers.lalr_parser	4	['N/A', 'N/A', 'N/A', 'N/A']	4	1	6	5	21	0	69	57
`lark.tools.standalone.gen_standalone`	lark.tools.standalone	4	['N/A', 'N/A', 'N/A', 'N/A']	2	23	3	4	22	2	74	56
`lark.lexer._create_unless`	lark.lexer	4	['N/A', 'N/A', 'N/A', 'N/A']	2	2	4	5	29	2	92	44
`lark.parser_frontends.create_earley_parser`	lark.parser_frontends	3	['N/A', 'N/A', 'N/A']	6	0	2	4	55	0	178	43
`lark.parsers.lalr_analysis.LALR_Analyzer.compute_lalr1_states`	lark.parsers.lalr_analysis	1	['N/A']	2	7	9	7	18	2	61	40

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

Functions statically reachable by fuzzers

155 / 623

Cyclomatic complexity statically reachable by fuzzers

578 / 2072

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_parse.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=['lark.visitors.Transformer_InPlace.transform', 'lark.lark.Lark.__init__', 'lark.utils._deserialize', 'lark.lexer.BasicLexer.__init__', 'lark.lexer._check_regex_collisions', 'lark.parser_frontends._wrap_lexer', 'lark.utils.Serialize.memo_serialize', 'lark.parser_frontends._construct_parsing_frontend', 'lark.lark.Lark._prepare_callbacks']

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
builder.used_files.keys	231	123	53.24%	['fuzz_parse']

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
	[]	[]
lark.parsers.xearley	[]	[]
lark.load_grammar	['fuzz_parse']	[]
os	[]	[]
lark.parser_frontends	['fuzz_parse']	[]
functools	[]	[]
logging	[]	[]
lark.parse_tree_builder	['fuzz_parse']	[]
lark.parsers.cyk	[]	[]
lark.reconstruct	[]	[]
getpass	[]	[]
lark.grammars	[]	[]
lark.__pyinstaller	[]	[]
rich	[]	[]
warnings	[]	[]
lark.parsers.earley_common	[]	[]
importlib	[]	[]
PyInstaller	[]	[]
pkgutil	[]	[]
contextlib	[]	[]
sre_parse	[]	[]
textwrap	[]	[]
lark.tools	[]	[]
lark.parsers.grammar_analysis	[]	[]
atheris	[]	[]
tempfile	[]	[]
lark.ast_utils	[]	[]
lark.common	['fuzz_parse']	[]
re	[]	[]
atomicwrites	[]	[]
random	[]	[]
lark.parsers.lalr_parser_state	[]	[]
lark.utils	['fuzz_parse']	[]
lark.visitors	['fuzz_parse']	[]
lark.parsers.lalr_parser	[]	[]
lark.tools.serialize	[]	[]
lark.parsers.earley_forest	[]	[]
collections	[]	[]
lark.grammar	['fuzz_parse']	[]
lark	[]	[]
lark.lexer	['fuzz_parse']	[]
Tree	[]	[]
lark.indenter	[]	[]
lark.tree	[]	[]
...fuzz_parse	['fuzz_parse']	[]
js2py	[]	[]
	[]	[]
lark.exceptions	[]	[]
lark.tree_templates	[]	[]
pydot	[]	[]
lark.__pyinstaller.hook-lark	[]	[]
interegular	[]	[]
pickle	[]	[]
lark.lark	['fuzz_parse']	[]
inspect	[]	[]
unicodedata	[]	[]
sys	[]	[]
regex	[]	[]
lark.tools.standalone	[]	[]
codecs	[]	[]
lark.tools.nearley	[]	[]
abc	[]	[]
lark.parsers	[]	[]
zlib	[]	[]
argparse	[]	[]
typing	[]	[]
json	[]	[]
operator	[]	[]
itertools	[]	[]
lark.parsers.lalr_analysis	[]	[]
hashlib	[]	[]
ast	[]	[]
lark.parsers.earley	[]	[]
lark.tree_matcher	[]	[]
copy	[]	[]
lark.parsers.lalr_interactive_parser	[]	[]
tokenize	[]	[]
base64	[]	[]

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_parse fuzzerLogFile-fuzz_parse.data fuzzerLogFile-fuzz_parse.data.yaml all_cov.json

Table of contents

Project overview: lark-parser

High level conclusions

Reachability and coverage overview

Fuzzers overview

Project functions overview

Fuzzer details

Fuzzer: fuzz_parse

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_parse.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