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

Table of contents

Project overview: pulldown-cmark
High level conclusions
Reachability and coverage overview
Fuzzers overview
Project functions overview
Fuzzer details
Fuzzer: parse
Call tree
Fuzz blockers
Runtime coverage analysis
Files reached
Fuzzer: commonmark_js
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
fuzz/fuzz_targets/parse.rs
Dictionary
Fuzzer function priority
fuzz/fuzz_targets/commonmark_js.rs
Dictionary
Fuzzer function priority
Runtime coverage analysis
Complex functions with low coverage
Fuzz driver synthesis
New fuzzers
Files and Directories in report
Files in report
Directories in report
Function call coverage
Function in each files in report
Metadata section
Sink analyser for CWEs
Report generation date: 2025-11-24

Project overview: pulldown-cmark

High level conclusions

Reachability and coverage overview

Functions statically reachable by fuzzers
0.0%
1 / 1653
Cyclomatic complexity statically reachable by fuzzers
0.0%
1 / 1398
Runtime code coverage of functions
14.0%
238 / 1653

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
parse fuzz/fuzz_targets/parse.rs 3 1652 17 15 0 1 parse.rs
commonmark_js fuzz/fuzz_targets/commonmark_js.rs 17 1652 19 18 0 4 commonmark_js.rs

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: 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 0 712 39.5%
gold [1:9] 1 0.05%
yellow [10:29] 0 0.0%
greenyellow [30:49] 0 0.0%
lawngreen 50+ 1086 60.3%
All colors 1799 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
54 959 delim_run_can_close call site: 00959 scan_entity
50 810 CodeDelims::find call site: 00810 CodeDelims::find
50 879 delim_run_can_open call site: 00879 CodeDelims::find
46 220 FirstPass::parse_footnote call site: 00220 InlineStack::push
37 346 scan_atx_heading call site: 00346 CodeDelims::insert
37 1148 extract_attribute_block_content_from_header_text call site: 01148 CodeDelims::insert
25 732 FirstPass::run call site: 00732 Tree::append_text
25 776 Allocations::allocate_alignment call site: 00776 delim_run_can_open
24 704 TreeIndex::add call site: 00704 FirstPass::run
23 116 LineStart::is_at_eol call site: 00116
22 151 CodeDelims::insert call site: 00151 CodeDelims::insert
19 21 FootnoteDefs::contains call site: 00021 special_bytes

Runtime coverage analysis

Covered functions
410
Functions that are reachable but not covered
1
Reachable functions
3
Percentage of reachable functions covered
66.67%
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.
Warning: The number of covered functions are larger than the number of reachable functions. This means that there are more functions covered at runtime than are extracted using static analysis. This is likely a result of the static analysis component failing to extract the right call graph or the coverage runtime being compiled with sanitizers in code that the static analysis has not analysed. This can happen if lto/gold is not used in all places that coverage instrumentation is used.
Function name source code lines source lines hit percentage hit

Files reached

filename functions hit
fuzz/fuzz_targets/parse.rs 3
pulldown-cmark/src/parse.rs 42
pulldown-cmark/src/firstpass.rs 214
pulldown-cmark/src/scanners.rs 94
dos-fuzzer/src/literals.rs 30
pulldown-cmark/src/tree.rs 18
dos-fuzzer/src/main.rs 1
pulldown-cmark/src/strings.rs 19
pulldown-cmark/src/lib.rs 1
pulldown-cmark/src/linklabel.rs 13
pulldown-cmark/tests/html.rs 5
pulldown-cmark/src/html.rs 5
pulldown-cmark/build.rs 8
pulldown-cmark/src/puncttable.rs 2
pulldown-cmark/src/entities.rs 3

Fuzzer: commonmark_js

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 1154 54.5%
gold [1:9] 0 0.0%
yellow [10:29] 6 0.28%
greenyellow [30:49] 1 0.04%
lawngreen 50+ 954 45.1%
All colors 2115 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
54 1045 delim_run_can_close call site: 01045 scan_entity
53 317 FirstPass::parse_block call site: 00317 FirstPass::parse_footnote
50 965 delim_run_can_open call site: 00965 CodeDelims::find
49 903 CodeDelims::find call site: 00903 CodeDelims::find
45 1442 FirstPass::parse_block call site: 01442 unescape
39 855 Tree::append call site: 00855 delim_run_can_open
37 1177 FirstPass::parse_line call site: 01177 FirstPass::parse_table
35 1251 HeadingIndex::get call site: 01251 parse_inside_attribute_block
33 1888 pulldown_cmark_fuzz::commonmark_js call site: 01888 get
25 825 FirstPass::run call site: 00825 Tree::append_text
22 1406 FirstPass::parse_block call site: 01406 LineStart::scan_blockquote_tag
20 462 &[u8]::get call site: 00462 CodeDelims::insert

Runtime coverage analysis

Covered functions
635
Functions that are reachable but not covered
12
Reachable functions
17
Percentage of reachable functions covered
29.41%
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.
Warning: The number of covered functions are larger than the number of reachable functions. This means that there are more functions covered at runtime than are extracted using static analysis. This is likely a result of the static analysis component failing to extract the right call graph or the coverage runtime being compiled with sanitizers in code that the static analysis has not analysed. This can happen if lto/gold is not used in all places that coverage instrumentation is used.
Function name source code lines source lines hit percentage hit

Files reached

filename functions hit
fuzz/fuzz_targets/commonmark_js.rs 14
pulldown-cmark/src/firstpass.rs 214
pulldown-cmark/src/parse.rs 42
dos-fuzzer/src/literals.rs 31
dos-fuzzer/src/main.rs 1
fuzz/src/lib.rs 71
pulldown-cmark/src/tree.rs 18
pulldown-cmark/src/strings.rs 19
pulldown-cmark/src/main.rs 2
pulldown-cmark/src/scanners.rs 94
pulldown-cmark/src/lib.rs 7
pulldown-cmark/src/linklabel.rs 13
pulldown-cmark/tests/html.rs 5
pulldown-cmark/src/html.rs 5
pulldown-cmark/build.rs 8
pulldown-cmark/src/puncttable.rs 2
pulldown-cmark/src/entities.rs 3
pulldown-cmark/tests/errors.rs 1

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

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

Functions statically reachable by fuzzers
0.0%
1 / 1653
Cyclomatic complexity statically reachable by fuzzers
0.0%
1 / 1398

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.

fuzz/fuzz_targets/parse.rs

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=['delim_run_can_close', 'CodeDelims::find', 'fuzz_target', 'FirstPass::parse_footnote', 'scan_atx_heading', 'extract_attribute_block_content_from_header_text', 'FirstPass::run', 'Allocations::allocate_alignment', 'TreeIndex::add', 'LineStart::is_at_eol']

fuzz/fuzz_targets/commonmark_js.rs

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=['delim_run_can_close', 'fuzz_target', 'delim_run_can_open', 'CodeDelims::find', 'Tree::append', 'FirstPass::parse_line', 'HeadingIndex::get', 'pulldown_cmark_fuzz::commonmark_js', 'FirstPass::run']

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
memchr::arch::generic::memchr::Onecore::core_arch::x86::__m128i::find_raw 63 30 47.61%
deflate 257 62 24.12%
inflate 612 335 54.73%
memchr::arch::generic::memchr::Threecore::core_arch::x86::__m128i::find_raw 63 26 41.26%
quick_xml::events::attributes::IterState::next 45 16 35.55%
quick_xml::reader::BangType::parse 32 9 28.12%
quick_xml::reader::parser::Parser::emit_bang 37 15 40.54%

Fuzz driver synthesis

New fuzzers

The below fuzzers are templates and suggestions for how to target the set of optimal functions above

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
/src/pulldown-cmark/pulldown-cmark/src/html.rs ['parse', 'commonmark_js'] ['parse', 'commonmark_js']
/src/pulldown-cmark/pulldown-cmark/tests/suite/gfm_strikethrough.rs [] []
/src/pulldown-cmark/pulldown-cmark/src/entities.rs ['parse', 'commonmark_js'] ['parse', 'commonmark_js']
/src/pulldown-cmark/pulldown-cmark/tests/suite/wikilinks.rs [] []
/src/pulldown-cmark/pulldown-cmark/src/utils.rs [] []
/src/pulldown-cmark/pulldown-cmark/tests/suite/gfm_tasklist.rs [] []
/src/pulldown-cmark/pulldown-cmark/tests/serde.rs [] []
/src/pulldown-cmark/dos-fuzzer/src/literals.rs ['parse', 'commonmark_js'] ['parse', 'commonmark_js']
/src/pulldown-cmark/pulldown-cmark/tests/suite/container_extensions.rs [] []
/src/pulldown-cmark/pulldown-cmark/tests/suite/spec.rs [] []
/src/pulldown-cmark/pulldown-cmark/tests/suite/regression.rs [] []
/src/pulldown-cmark/dos-fuzzer/src/scoring.rs [] []
/src/pulldown-cmark/dos-fuzzer/src/black_box.rs [] []
/src/pulldown-cmark/pulldown-cmark/src/lib.rs ['parse', 'commonmark_js'] ['parse', 'commonmark_js']
/src/pulldown-cmark/pulldown-cmark/tests/suite/smart_punct.rs [] []
/src/pulldown-cmark/guide/prepare-specs.rs [] []
/src/pulldown-cmark/fuzz/fuzz_targets/parse.rs ['parse'] []
/src/pulldown-cmark/pulldown-cmark/tests/lib.rs [] []
/src/pulldown-cmark/pulldown-cmark/tests/suite/table.rs [] []
/src/pulldown-cmark/pulldown-cmark/tests/suite/strikethrough.rs [] []
/src/pulldown-cmark/bench/benches/markdown-it.rs [] []
/src/pulldown-cmark/pulldown-cmark/src/scanners.rs ['parse', 'commonmark_js'] ['parse', 'commonmark_js']
/src/pulldown-cmark/pulldown-cmark/src/strings.rs ['parse', 'commonmark_js'] ['parse', 'commonmark_js']
/src/pulldown-cmark/pulldown-cmark/tests/suite/blockquotes_tags.rs [] []
/src/pulldown-cmark/dos-fuzzer/src/clock.rs [] []
/src/pulldown-cmark/pulldown-cmark/tests/suite/metadata_blocks.rs [] []
/src/pulldown-cmark/pulldown-cmark/tests/suite/old_footnotes.rs [] []
/src/pulldown-cmark/pulldown-cmark/build.rs ['parse', 'commonmark_js'] ['parse', 'commonmark_js']
/src/pulldown-cmark/fuzz/src/lib.rs ['commonmark_js'] ['commonmark_js']
/src/pulldown-cmark/pulldown-cmark/tests/suite/math.rs [] []
/src/pulldown-cmark/pulldown-cmark/src/firstpass.rs ['parse', 'commonmark_js'] ['parse', 'commonmark_js']
/src/pulldown-cmark/fuzz/fuzz_targets/commonmark_js.rs ['commonmark_js'] []
/src/pulldown-cmark/pulldown-cmark-escape/src/lib.rs [] []
/src/pulldown-cmark/bench/benches/html_rendering.rs [] []
/src/pulldown-cmark/pulldown-cmark/src/parse.rs ['parse', 'commonmark_js'] ['parse', 'commonmark_js']
/src/pulldown-cmark/pulldown-cmark/src/tree.rs ['parse', 'commonmark_js'] ['parse', 'commonmark_js']
/src/pulldown-cmark/pulldown-cmark/src/linklabel.rs ['parse', 'commonmark_js'] ['parse', 'commonmark_js']
/src/pulldown-cmark/dos-fuzzer/src/main.rs ['parse', 'commonmark_js'] ['parse', 'commonmark_js']
/src/pulldown-cmark/bench/benches/lib.rs [] []
/src/pulldown-cmark/pulldown-cmark/tests/html.rs ['parse', 'commonmark_js'] []
/src/pulldown-cmark/pulldown-cmark/examples/normalize-wikilink.rs [] []
/src/pulldown-cmark/pulldown-cmark/tests/suite/gfm_table.rs [] []
/src/pulldown-cmark/pulldown-cmark/tests/suite/heading_attrs.rs [] []
/src/pulldown-cmark/pulldown-cmark/src/main.rs ['commonmark_js'] []
/src/pulldown-cmark/pulldown-cmark/tests/errors.rs ['commonmark_js'] ['commonmark_js']
/src/pulldown-cmark/pulldown-cmark/src/puncttable.rs ['parse', 'commonmark_js'] ['parse', 'commonmark_js']
/src/pulldown-cmark/pulldown-cmark/tests/suite/super_sub.rs [] []
/src/pulldown-cmark/pulldown-cmark/tests/suite/footnotes.rs [] []
/src/pulldown-cmark/pulldown-cmark/tests/suite/definition_lists.rs [] []

Directories in report

Directory
/src/pulldown-cmark/bench/benches/
/src/pulldown-cmark/pulldown-cmark/
/src/pulldown-cmark/pulldown-cmark/src/
/src/pulldown-cmark/pulldown-cmark/examples/
/src/pulldown-cmark/fuzz/fuzz_targets/
/src/pulldown-cmark/guide/
/src/pulldown-cmark/pulldown-cmark/tests/
/src/pulldown-cmark/pulldown-cmark-escape/src/
/src/pulldown-cmark/fuzz/src/
/src/pulldown-cmark/pulldown-cmark/tests/suite/
/src/pulldown-cmark/dos-fuzzer/src/

Function call coverage

This section shows a list of 3rd party function calls and their relative coverage information. By static analysis of the target project code, all of the 3rd party function call and their caller information, including the source file and line number that initiate the call are captured. The caller source code file and line number are shown in column 2 while column 1 is the function name of the 3rd party function call. Each occurrent of the 3rd party function call will occuply a separate row. Column 3 of each row indicate if the 3rd party call in the source file line is unreachable. Column 4 lists all fuzzers that have covered that particular system call in that specific location (source file and line)during their dynamic fuzzing.

Function in each files in report

Target sink Callsite location Reached by fuzzer Covered by Fuzzers

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
parse fuzzerLogFile-parse.data fuzzerLogFile-parse.data.yaml parse.covreport
commonmark_js fuzzerLogFile-commonmark_js.data fuzzerLogFile-commonmark_js.data.yaml commonmark_js.covreport

Sink analyser for CWEs

No sink functions/methods found in the target project.