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

Table of contents

Project overview: ron
High level conclusions
Reachability and coverage overview
Fuzzers overview
Project functions overview
Fuzzer details
Fuzzer: from_str
Call tree
Fuzz blockers
Runtime coverage analysis
Files reached
Fuzzer: arbitrary
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/from_str.rs
Dictionary
Fuzzer function priority
fuzz/fuzz_targets/arbitrary.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: 2025-07-11

Project overview: ron

High level conclusions

Reachability and coverage overview

Functions statically reachable by fuzzers
0.0%
1 / 841
Cyclomatic complexity statically reachable by fuzzers
0.0%
2 / 1445
Runtime code coverage of functions
33.0%
276 / 841

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
from_str fuzz/fuzz_targets/from_str.rs 4 840 19 14 0 2 from_str.rs
arbitrary fuzz/fuzz_targets/arbitrary.rs 3 840 26 16 0 1 arbitrary.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: from_str

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 0 178 48.3%
gold [1:9] 5 1.35%
yellow [10:29] 13 3.53%
greenyellow [30:49] 3 0.81%
lawngreen 50+ 169 45.9%
All colors 368 100

Fuzz blockers

The following nodes represent call sites where fuzz blockers occur.

Amount of callsites blocked Calltree index Parent function Callsite Largest blocked function
93 179 Options::default call site: 00179 Parser::extensions
40 134 Deserializer::from_str_with_options call site: 00134 Parser::extensions
6 114 Options::default call site: 00114 Options::from_str
5 86 Parser::consume_all call site: 00086 Parser::consume_all
5 93 Parser::consume_all call site: 00093 Parser::skip_ws
4 273 Parser::consume_all call site: 00273 Parser::skip_ws
4 328 Parser::consume_all call site: 00328 Parser::skip_ws
3 8 Parser::next_chars_while_len call site: 00008 Options::to_string
3 33 Parser::peek_char call site: 00033
3 364 Parser::new call site: 00364 Serializer::with_options
2 16 Parser::skip_ws call site: 00016
2 106 Parser::skip_ws call site: 00106

Runtime coverage analysis

Covered functions
353
Functions that are reachable but not covered
3
Reachable functions
4
Percentage of reachable functions covered
25.0%
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.
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/from_str.rs 4
src/parse.rs 46
src/options.rs 15
src/ser/path_meta.rs 4
tests/escape.rs 2
src/error.rs 4
src/ser/mod.rs 9
tests/307_stack_overflow.rs 10
tests/337_value_float_roundtrip.rs 6
src/de/mod.rs 2
tests/511_deserialize_any_map_string_key.rs 3
tests/407_raw_value.rs 18
tests/438_rusty_byte_strings.rs 14
src/extensions.rs 4

Fuzzer: arbitrary

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 0 389 37.4%
gold [1:9] 21 2.01%
yellow [10:29] 30 2.88%
greenyellow [30:49] 2 0.19%
lawngreen 50+ 598 57.4%
All colors 1040 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
46 192 RawValue::from_ron call site: 00192 Parser::consume_all
42 121 Options::default call site: 00121 Parser::extensions
29 342 Deserializer::from_str_with_options call site: 00342 SerdeDataType::arbitrary_value
26 1012 ron::de::Deserializer::from_str_with_options call site: 01012 Parser::extensions
12 730 SerdeDataType::supported_inside_untagged call site: 00730 SerdeDataType::supported_inside_untagged
12 758 SerdeDataType::supported_inside_untagged call site: 00758 SerdeDataType::supported_inside_untagged
8 177 RawValue::from_ron call site: 00177 Options::from_str
7 778 SerdeDataType::supported_flattened_map_inside_flatten_field call site: 00778
7 965 SerdeDataType::arbitrary_value call site: 00965 SerdeDataType::arbitrary_value
7 991 typed_data::roundtrip_arbitrary_typed_ron_or_panic call site: 00991 Options::to_string_pretty
6 10 typed_data::roundtrip_arbitrary_typed_ron_or_panic call site: 00010 Options::from_str
6 1000 TypedSerdeData::pretty_config call site: 01000 RawValue::to_owned

Runtime coverage analysis

Covered functions
3183
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/arbitrary.rs 3
src/parse.rs 46
fuzz/fuzz_targets/bench/lib.rs 67
tests/337_value_float_roundtrip.rs 6
src/options.rs 16
src/de/mod.rs 2
src/ser/path_meta.rs 7
tests/escape.rs 2
src/error.rs 4
src/ser/mod.rs 9
tests/307_stack_overflow.rs 10
tests/511_deserialize_any_map_string_key.rs 3
tests/407_raw_value.rs 18
tests/438_rusty_byte_strings.rs 14
src/extensions.rs 4
src/value/raw.rs 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 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 / 841
Cyclomatic complexity statically reachable by fuzzers
0.0%
2 / 1445

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/from_str.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=['Options::default', 'Deserializer::from_str_with_options', 'Parser::consume_all', 'Parser::next_chars_while_len', 'Parser::peek_char', 'Parser::new']

fuzz/fuzz_targets/arbitrary.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=['RawValue::from_ron', 'Options::default', 'Deserializer::from_str_with_options', 'ron::de::Deserializer::from_str_with_options', 'SerdeDataType::supported_inside_untagged', 'SerdeDataType::supported_flattened_map_inside_flatten_field', 'SerdeDataType::arbitrary_value', 'typed_data::roundtrip_arbitrary_typed_ron_or_panic']

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
ron::de::Deserializer::handle_any_struct::ron::de::value::ValueVisitor 39 20 51.28%
arbitrary::typed_data::SerdeDataType::supported_inside_internally_tagged_newtype 49 24 48.97%
arbitrary::typed_data::BorrowedTypedSerdeData as serde::ser::Serialize::serialize::ron::ser::raw::Serializer&mut alloc::string::String 437 4 0.915%
arbitrary::typed_data::BorrowedTypedSerdeData as serde::de::DeserializeSeed::deserialize::serde::__private::de::FlatMapDeserializerron::error::Error 391 175 44.75%
ron::de::Deserializer::handle_any_struct::serde_path_to_error::de::CaptureKeyserde::__private::de::content::TaggedContentVisitorarbitrary::typed_data::BorrowedTypedSerdeData as serde::de::DeserializeSeed::deserialize::DelayedVariantIdentifier 39 17 43.58%
ron::de::Deserializer::handle_any_struct::serde_path_to_error::wrap::Wrapserde::__private::de::content::TaggedContentVisitorarbitrary::typed_data::BorrowedTypedSerdeData as serde::de::DeserializeSeed::deserialize::DelayedVariantIdentifier 39 17 43.58%
ron::de::Deserializer::handle_any_struct::serde::__private::de::content::TaggedContentVisitorarbitrary::typed_data::BorrowedTypedSerdeData as serde::de::DeserializeSeed::deserialize::DelayedVariantIdentifier 39 17 43.58%
&mut ron::de::Deserializer as serde::de::Deserializer::deserialize_any::serde_path_to_error::de::CaptureKeyserde::__private::de::content::TaggedContentVisitorarbitrary::typed_data::BorrowedTypedSerdeData as serde::de::DeserializeSeed::deserialize::DelayedVariantIdentifier 55 23 41.81%
&mut ron::de::Deserializer as serde::de::Deserializer::deserialize_any::serde_path_to_error::wrap::Wraparbitrary::typed_data::BorrowedTypedSerdeData as serde::de::DeserializeSeed::deserialize::FlattenStructVariantSeed 55 22 40.0%
&mut ron::de::Deserializer as serde::de::Deserializer::deserialize_any::arbitrary::typed_data::BorrowedTypedSerdeData as serde::de::DeserializeSeed::deserialize::FlattenStructVariantSeed 55 22 40.0%
ron::de::Deserializer::handle_any_struct::serde::de::ignored_any::IgnoredAny 39 20 51.28%
&mut ron::de::Deserializer as serde::de::Deserializer::deserialize_newtype_struct::&ron::value::raw::RawValue as serde::de::Deserialize::deserialize::ReferenceVisitor 41 21 51.21%
ron::error::Error as core::fmt::Display::fmt 131 12 9.160%
ron::parse::Parser::integer::i8 114 30 26.31%
ron::parse::Parser::integer::i32 114 32 28.07%
ron::parse::Parser::integer::u32 114 34 29.82%
ron::parse::Parser::integer::i128 114 38 33.33%
ron::parse::Parser::integer::u128 114 37 32.45%
ron::parse::Parser::integer::i16 114 31 27.19%
ron::parse::Parser::integer::u16 114 33 28.94%
ron::parse::Parser::integer::i64 114 33 28.94%
ron::parse::Parser::integer::u64 114 35 30.70%
ron::parse::Parser::integer::u8 114 32 28.07%

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/ron/tests/522_explicit_struct_names.rs [] []
/src/ron/src/value/mod.rs [] []
/src/ron/tests/117_untagged_tuple_variant.rs [] []
/src/ron/tests/367_implicit_some.rs [] []
/src/ron/tests/min_max.rs [] []
/src/ron/src/ser/mod.rs ['from_str', 'arbitrary'] ['from_str', 'arbitrary']
/src/ron/tests/roundtrip.rs [] []
/src/ron/tests/511_deserialize_any_map_string_key.rs ['from_str', 'arbitrary'] []
/src/ron/tests/502_known_bugs.rs [] []
/src/ron/src/util/span_substring.rs [] []
/src/ron/tests/425_escape_strings.rs [] []
/src/ron/src/de/mod.rs ['from_str', 'arbitrary'] ['from_str', 'arbitrary']
/src/ron/tests/321_unicode_ident.rs [] []
/src/ron/tests/508_value_adjacently_tagged_bug.rs [] []
/src/ron/src/de/id.rs [] []
/src/ron/tests/447_compact_maps_structs.rs [] []
/src/ron/tests/to_string_pretty.rs [] []
/src/ron/src/ser/raw.rs [] []
/src/ron/src/value/map.rs [] []
/src/ron/fuzz/fuzz_targets/bench/lib.rs ['arbitrary'] ['arbitrary']
/src/ron/tests/217_nested_untagged_enums.rs [] []
/src/ron/tests/value.rs [] []
/src/ron/tests/options.rs [] []
/src/ron/src/de/tests.rs [] []
/src/ron/tests/big_struct.rs [] []
/src/ron/tests/526_flatten.rs [] []
/src/ron/tests/322_escape_idents.rs [] []
/src/ron/src/ser/value.rs [] []
/src/ron/tests/extensions.rs [] []
/src/ron/tests/481_number_underscores_suffixes.rs [] []
/src/ron/tests/530_untagged_union.rs [] []
/src/ron/tests/floats.rs [] []
/src/ron/src/value/raw.rs ['arbitrary'] ['arbitrary']
/src/ron/tests/depth_limit.rs [] []
/src/ron/fuzz/fuzz_targets/bench/main.rs [] []
/src/ron/tests/250_variant_newtypes.rs [] []
/src/ron/src/value/number.rs [] []
/src/ron/tests/non_string_tag.rs [] []
/src/ron/tests/254_typetag.rs [] []
/src/ron/tests/207_adjacently_tagged_enum.rs [] []
/src/ron/tests/465_ser_backslash_string.rs [] []
/src/ron/tests/370_float_parsing.rs [] []
/src/ron/tests/401_raw_identifier.rs [] []
/src/ron/tests/465_implicit_some_stack.rs [] []
/src/ron/tests/492_enum_in_untagged_enum.rs [] []
/src/ron/tests/unicode.rs [] []
/src/ron/fuzz/fuzz_targets/from_str.rs ['from_str'] []
/src/ron/examples/base64.rs [] []
/src/ron/tests/359_deserialize_seed.rs [] []
/src/ron/src/extensions.rs ['from_str', 'arbitrary'] ['from_str', 'arbitrary']
/src/ron/tests/preserve_sequence.rs [] []
/src/ron/tests/240_array_pretty.rs [] []
/src/ron/tests/289_enumerate_arrays.rs [] []
/src/ron/tests/337_value_float_roundtrip.rs ['from_str', 'arbitrary'] []
/src/ron/src/parse.rs ['from_str', 'arbitrary'] ['from_str', 'arbitrary']
/src/ron/tests/423_de_borrowed_identifier.rs [] []
/src/ron/src/ser/path_meta.rs ['from_str', 'arbitrary'] ['from_str', 'arbitrary']
/src/ron/tests/129_indexmap.rs [] []
/src/ron/tests/449_tagged_enum.rs [] []
/src/ron/tests/465_unwrap_some_newtype_variant_value.rs [] []
/src/ron/tests/564_exhaustive_number.rs [] []
/src/ron/src/ser/tests.rs [] []
/src/ron/tests/115_minimal_flattening.rs [] []
/src/ron/examples/file_read_write_vec.rs [] []
/src/ron/tests/462_bytes.rs [] []
/src/ron/tests/203_error_positions.rs [] []
/src/ron/tests/147_empty_sets_serialisation.rs [] []
/src/ron/tests/comments.rs [] []
/src/ron/tests/numbers.rs [] []
/src/ron/tests/438_rusty_byte_strings.rs ['from_str', 'arbitrary'] []
/src/ron/tests/307_stack_overflow.rs ['from_str', 'arbitrary'] []
/src/ron/tests/large_number.rs [] []
/src/ron/tests/borrowed_str.rs [] []
/src/ron/tests/357_untagged_enum_roundtrip.rs [] []
/src/ron/examples/encode.rs [] []
/src/ron/src/de/value.rs [] []
/src/ron/tests/non_identifier_identifier.rs [] []
/src/ron/tests/465_validate_ser_identifiers.rs [] []
/src/ron/tests/436_untagged_bytes.rs [] []
/src/ron/tests/465_r_name_value.rs [] []
/src/ron/tests/escape.rs ['from_str', 'arbitrary'] []
/src/ron/tests/301_struct_name_mismatch.rs [] []
/src/ron/tests/407_raw_value.rs ['from_str', 'arbitrary'] []
/src/ron/tests/410_trailing_comma.rs [] []
/src/ron/src/options.rs ['from_str', 'arbitrary'] ['from_str', 'arbitrary']
/src/ron/tests/544_path_meta.rs [] []
/src/ron/fuzz/fuzz_targets/arbitrary.rs ['arbitrary'] []
/src/ron/tests/393_serde_errors.rs [] []
/src/ron/src/error.rs ['from_str', 'arbitrary'] ['from_str', 'arbitrary']
/src/ron/tests/123_enum_representation.rs [] []
/src/ron/tests/256_comma_error.rs [] []
/src/ron/tests/152_bitflags.rs [] []

Directories in report

Directory
/src/ron/tests/
/src/ron/fuzz/fuzz_targets/bench/
/src/ron/fuzz/fuzz_targets/
/src/ron/src/value/
/src/ron/src/ser/
/src/ron/src/
/src/ron/src/util/
/src/ron/src/de/
/src/ron/examples/

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
from_str fuzzerLogFile-from_str.data fuzzerLogFile-from_str.data.yaml from_str.covreport
arbitrary fuzzerLogFile-arbitrary.data fuzzerLogFile-arbitrary.data.yaml arbitrary.covreport

Sink analyser for CWEs

No sink functions/methods found in the target project.