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

Table of contents

Project overview: quick-xml
High level conclusions
Reachability and coverage overview
Fuzzers overview
Project functions overview
Fuzzer details
Fuzzer: fuzz_target_1
Call tree
Fuzz blockers
Runtime coverage analysis
Files reached
Fuzzer: structured_roundtrip
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/fuzz_target_1.rs
Dictionary
Fuzzer function priority
fuzz/fuzz_targets/structured_roundtrip.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: 2025-08-26

Project overview: quick-xml

High level conclusions

Reachability and coverage overview

Functions statically reachable by fuzzers
2.0%
25 / 1293
Cyclomatic complexity statically reachable by fuzzers
4.0%
60 / 1348
Runtime code coverage of functions
27.0%
343 / 1293

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_target_1 fuzz/fuzz_targets/fuzz_target_1.rs 69 1277 14 21 0 37 fuzz_target_1.rs
structured_roundtrip fuzz/fuzz_targets/structured_roundtrip.rs 63 1277 14 18 0 24 structured_roundtrip.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: fuzz_target_1

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 0 601 91.6%
gold [1:9] 0 0.0%
yellow [10:29] 0 0.0%
greenyellow [30:49] 0 0.0%
lawngreen 50+ 55 8.38%
All colors 656 100

Fuzz blockers

The following nodes represent call sites where fuzz blockers occur.

Amount of callsites blocked Calltree index Parent function Callsite Largest blocked function
142 513 parse_number call site: 00513 round_trip
123 89 QName::prefix call site: 00089 NamespaceResolver::push
91 377 from_str_radix call site: 00377 NamespaceResolver::push
56 311 Decoder::decode call site: 00311 Decoder::decode_into
49 255 Option::len call site: 00255 NamespaceResolver::push
35 3 Reader::from_reader call site: 00003 round_trip
28 45 Reader::from_str call site: 00045 NsReader::read_resolved_event
22 474 Writer::write_wrapped call site: 00474 Writer::write_wrapped
20 234 name_len call site: 00234 NamespaceResolver::push
12 76 QName::prefix call site: 00076 trivial::byte_buf
10 216 IterState::new call site: 00216 QName::as_namespace_binding
5 368 &[u8]::len call site: 00368 parse_number

Runtime coverage analysis

Covered functions
289
Functions that are reachable but not covered
39
Reachable functions
69
Percentage of reachable functions covered
43.48%
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/fuzz_target_1.rs 26
src/reader/ns_reader.rs 40
src/name.rs 46
src/se/mod.rs 5
src/utils.rs 5
src/de/simple_type.rs 2
src/events/mod.rs 19
tests/reader-namespaces.rs 2
tests/serde_helpers/mod.rs 5
tests/serde-migrated.rs 8
src/events/attributes.rs 12
tests/serde-de.rs 1
tests/serde-de-enum.rs 16
src/writer.rs 39
src/encoding.rs 19
tests/escape.rs 37
tests/html.rs 11
src/escape.rs 12
tests/writer-indentation.rs 7
tests/roundtrip.rs 2
tests/writer.rs 7

Fuzzer: structured_roundtrip

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 0 360 70.3%
gold [1:9] 3 0.58%
yellow [10:29] 6 1.17%
greenyellow [30:49] 0 0.0%
lawngreen 50+ 143 27.9%
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
59 255 NsReader::process_event call site: 00255 NsReader::read_resolved_event
49 198 NamespaceResolver::pop call site: 00198 read_event_impl
44 132 Reader::from_str call site: 00132 NsReader::read_resolved_event
23 88 fuzz_round_trip call site: 00088 SpecIter::next
21 42 Writer::write_wrapped call site: 00042 Writer::write_wrapped
19 410 ElementWriter::write_text_content call site: 00410 Writer::write_wrapped
14 73 fuzz_round_trip call site: 00073 Decoder::decode_into
13 437 ElementWriter::write_text_content call site: 00437 read_to_end
12 184 NamespaceResolver::pop call site: 00184 trivial::byte_buf
12 386 BytesStart::push_attr call site: 00386 Decoder::decode_into
11 14 fuzz_round_trip call site: 00014 decode_into
11 368 BytesStart::push_attr call site: 00368 Decoder::decode_into

Runtime coverage analysis

Covered functions
352
Functions that are reachable but not covered
29
Reachable functions
63
Percentage of reachable functions covered
53.97%
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/structured_roundtrip.rs 30
src/se/mod.rs 2
src/utils.rs 5
src/de/simple_type.rs 2
src/writer.rs 42
src/encoding.rs 12
tests/roundtrip.rs 2
src/events/mod.rs 20
tests/html.rs 11
src/name.rs 46
tests/serde-de-enum.rs 16
tests/serde_helpers/mod.rs 5
src/reader/ns_reader.rs 45
tests/reader-namespaces.rs 2
src/events/attributes.rs 5
tests/serde-de.rs 1
tests/serde-migrated.rs 5
fuzz/fuzz_targets/fuzz_target_1.rs 2

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
2.0%
25 / 1293
Cyclomatic complexity statically reachable by fuzzers
4.0%
60 / 1348

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/fuzz_target_1.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=['parse_number', 'QName::prefix', 'from_str_radix', 'Decoder::decode', 'Option::len', 'Reader::from_reader', 'Reader::from_str', 'Writer::write_wrapped', 'name_len']

fuzz/fuzz_targets/structured_roundtrip.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=['NsReader::process_event', 'NamespaceResolver::pop', 'Reader::from_str', 'fuzz_round_trip', 'Writer::write_wrapped', 'ElementWriter::write_text_content', 'BytesStart::push_attr']

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 71 35 49.29%
memchr::arch::generic::memchr::Threecore::core_arch::x86::__m128i::find_raw 69 35 50.72%

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/quick-xml/src/de/map.rs [] []
/src/quick-xml/tests/reader-attributes.rs [] []
/src/quick-xml/tests/reader-references.rs [] []
/src/quick-xml/tests/helpers/mod.rs [] []
/src/quick-xml/src/parser/pi.rs [] []
/src/quick-xml/src/de/mod.rs [] []
/src/quick-xml/tests/reader-errors.rs [] []
/src/quick-xml/compare/benches/low-level.rs [] []
/src/quick-xml/tests/roundtrip.rs ['fuzz_target_1', 'structured_roundtrip'] ['fuzz_target_1', 'structured_roundtrip']
/src/quick-xml/src/se/simple_type.rs [] []
/src/quick-xml/tests/serde-de-seq.rs [] []
/src/quick-xml/src/writer.rs ['fuzz_target_1', 'structured_roundtrip'] ['fuzz_target_1', 'structured_roundtrip']
/src/quick-xml/tests/reader-config.rs [] []
/src/quick-xml/src/se/mod.rs ['fuzz_target_1', 'structured_roundtrip'] ['fuzz_target_1', 'structured_roundtrip']
/src/quick-xml/tests/reader-namespaces.rs ['fuzz_target_1', 'structured_roundtrip'] []
/src/quick-xml/src/reader/state.rs [] []
/src/quick-xml/src/events/attributes.rs ['fuzz_target_1', 'structured_roundtrip'] ['fuzz_target_1', 'structured_roundtrip']
/src/quick-xml/src/de/attributes.rs [] []
/src/quick-xml/tests/serde-issues.rs [] []
/src/quick-xml/tests/writer-indentation.rs ['fuzz_target_1'] []
/src/quick-xml/tests/issues.rs [] []
/src/quick-xml/src/serde_helpers.rs [] []
/src/quick-xml/compare/benches/serde.rs [] []
/src/quick-xml/src/name.rs ['fuzz_target_1', 'structured_roundtrip'] ['fuzz_target_1', 'structured_roundtrip']
/src/quick-xml/src/events/mod.rs ['fuzz_target_1', 'structured_roundtrip'] ['fuzz_target_1', 'structured_roundtrip']
/src/quick-xml/src/escape.rs ['fuzz_target_1'] ['fuzz_target_1']
/src/quick-xml/tests/serde-de-xsi.rs [] []
/src/quick-xml/src/parser/element.rs [] []
/src/quick-xml/tests/serde-de-enum.rs ['fuzz_target_1', 'structured_roundtrip'] ['fuzz_target_1', 'structured_roundtrip']
/src/quick-xml/src/se/text.rs [] []
/src/quick-xml/fuzz/fuzz_targets/fuzz_target_1.rs ['fuzz_target_1', 'structured_roundtrip'] ['structured_roundtrip']
/src/quick-xml/tests/reader.rs [] []
/src/quick-xml/src/utils.rs ['fuzz_target_1', 'structured_roundtrip'] ['fuzz_target_1', 'structured_roundtrip']
/src/quick-xml/src/de/text.rs [] []
/src/quick-xml/examples/flattened_enum.rs [] []
/src/quick-xml/examples/read_nodes.rs [] []
/src/quick-xml/src/de/var.rs [] []
/src/quick-xml/src/de/simple_type.rs ['fuzz_target_1', 'structured_roundtrip'] ['fuzz_target_1', 'structured_roundtrip']
/src/quick-xml/src/de/resolver.rs [] []
/src/quick-xml/src/writer/async_tokio.rs [] []
/src/quick-xml/fuzz/fuzz_targets/structured_roundtrip.rs ['structured_roundtrip'] ['structured_roundtrip']
/src/quick-xml/benches/macrobenches.rs [] []
/src/quick-xml/src/se/key.rs [] []
/src/quick-xml/src/de/key.rs [] []
/src/quick-xml/benches/microbenches.rs [] []
/src/quick-xml/examples/read_texts.rs [] []
/src/quick-xml/src/reader/mod.rs [] []
/src/quick-xml/examples/custom_entities.rs [] []
/src/quick-xml/src/reader/ns_reader.rs ['fuzz_target_1', 'structured_roundtrip'] ['fuzz_target_1', 'structured_roundtrip']
/src/quick-xml/src/reader/buffered_reader.rs [] []
/src/quick-xml/tests/writer.rs ['fuzz_target_1'] ['fuzz_target_1']
/src/quick-xml/tests/serde_roundtrip.rs [] []
/src/quick-xml/tests/serde-migrated.rs ['fuzz_target_1', 'structured_roundtrip'] []
/src/quick-xml/tests/serde-de.rs ['fuzz_target_1', 'structured_roundtrip'] ['fuzz_target_1', 'structured_roundtrip']
/src/quick-xml/tests/escape.rs ['fuzz_target_1'] []
/src/quick-xml/src/reader/async_tokio.rs [] []
/src/quick-xml/src/se/element.rs [] []
/src/quick-xml/tests/async-tokio.rs [] []
/src/quick-xml/src/reader/slice_reader.rs [] []
/src/quick-xml/tests/fuzzing.rs [] []
/src/quick-xml/src/errors.rs [] []
/src/quick-xml/src/encoding.rs ['fuzz_target_1', 'structured_roundtrip'] ['fuzz_target_1', 'structured_roundtrip']
/src/quick-xml/tests/html.rs ['fuzz_target_1', 'structured_roundtrip'] ['fuzz_target_1', 'structured_roundtrip']
/src/quick-xml/tests/encodings.rs [] []
/src/quick-xml/src/se/content.rs [] []
/src/quick-xml/test-gen/src/main.rs [] []

Directories in report

Directory
/src/quick-xml/src/reader/
/src/quick-xml/src/parser/
/src/quick-xml/tests/helpers/
/src/quick-xml/src/events/
/src/quick-xml/src/de/
/src/quick-xml/src/writer/
/src/quick-xml/test-gen/src/
/src/quick-xml/fuzz/fuzz_targets/
/src/quick-xml/src/se/
/src/quick-xml/tests/
/src/quick-xml/examples/
/src/quick-xml/src/
/src/quick-xml/compare/benches/
/src/quick-xml/benches/

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
fuzz_target_1 fuzzerLogFile-fuzz_target_1.data fuzzerLogFile-fuzz_target_1.data.yaml fuzz_target_1.covreport
structured_roundtrip fuzzerLogFile-structured_roundtrip.data fuzzerLogFile-structured_roundtrip.data.yaml structured_roundtrip.covreport

Sink analyser for CWEs

No sink functions/methods found in the target project.