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

Table of contents

Project overview: xlsxwriter
High level conclusions
Reachability and coverage overview
Fuzzers overview
Project functions overview
Fuzzer details
Fuzzer: xlsx_fuzzer
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
dev/fuzzing/xlsx_fuzzer.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: 2025-07-01

Project overview: xlsxwriter

High level conclusions

Reachability and coverage overview

Functions statically reachable by fuzzers
0.0%
0 / 1048
Cyclomatic complexity statically reachable by fuzzers
0.0%
0 / 3810
Runtime code coverage of functions
23.0%
246 / 1048

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
xlsx_fuzzer dev/fuzzing/xlsx_fuzzer.py 12 1389 1 2 0 33 xlsx_fuzzer.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: xlsx_fuzzer

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 12 85.7%
gold [1:9] 0 0.0%
yellow [10:29] 0 0.0%
greenyellow [30:49] 0 0.0%
lawngreen 50+ 2 14.2%
All colors 14 100

Fuzz blockers

The following nodes represent call sites where fuzz blockers occur.

Amount of callsites blocked Calltree index Parent function Callsite Largest blocked function
9 4 ...XlsxWriter.dev.fuzzing.xlsx_fuzzer.TestOneInput call site: 00004 fuzz_helpers.EnhancedFuzzedDataProvider.PickValueInList
3 0 EP call site: 00000 fuzz_helpers.EnhancedFuzzedDataProvider

Runtime coverage analysis

Covered functions
304
Functions that are reachable but not covered
11
Reachable functions
12
Percentage of reachable functions covered
8.33%
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.
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
/ 1
...XlsxWriter.dev.fuzzing.xlsx_fuzzer 11

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
xlsxwriter.workbook.Workbook.close xlsxwriter.workbook 1 ['N/A'] 7 0 4 2 4 441 1 1423 1414
xlsxwriter.chart.Chart._write_plot_area xlsxwriter.chart 1 ['N/A'] 8 0 16 5 5 235 0 799 739
xlsxwriter.worksheet.Worksheet._assemble_xml_file xlsxwriter.worksheet 1 ['N/A'] 5 0 32 2 4 170 0 640 508
xlsxwriter.worksheet.convert_range_args.cell_wrapper xlsxwriter.worksheet 3 ['N/A', 'N/A', 'N/A'] 7 0 2 2 4 145 0 573 358
xlsxwriter.drawing.Drawing._write_two_cell_anchor xlsxwriter.drawing 3 ['N/A', 'N/A', 'N/A'] 4 0 11 5 5 88 1 293 222
xlsxwriter.workbook.Workbook.add_chart xlsxwriter.workbook 2 ['N/A', 'N/A'] 4 0 4 11 7 78 0 286 121
xlsxwriter.worksheet.Worksheet.embed_image xlsxwriter.worksheet 5 ['N/A', 'N/A', 'N/A', 'N/A', 'N/A'] 7 0 4 4 5 81 1 296 69
xlsxwriter.chart.Chart._write_chart xlsxwriter.chart 1 ['N/A'] 7 0 10 4 5 210 1 708 63
xlsxwriter.chart.Chart.add_series xlsxwriter.chart 2 ['N/A', 'N/A'] 4 0 5 13 8 62 0 239 60
xlsxwriter.worksheet.Worksheet._prepare_shape xlsxwriter.worksheet 3 ['N/A', 'N/A', 'N/A'] 6 0 3 3 4 45 0 171 56

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

Functions statically reachable by fuzzers
75.0%
783 / 1048
Cyclomatic complexity statically reachable by fuzzers
76.0%
2881 / 3810

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.

dev/fuzzing/xlsx_fuzzer.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=['...XlsxWriter.dev.fuzzing.xlsx_fuzzer.TestOneInput']

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
xlsxwriter.workbook.Workbook.add_chart 31 0 0.0% []
xlsxwriter.workbook.Workbook._prepare_drawings 84 21 25.0% ['xlsx_fuzzer']
xlsxwriter.workbook.Workbook._add_chart_data 36 7 19.44% ['xlsx_fuzzer']
xlsxwriter.format.Format.set_align 35 0 0.0% []
xlsxwriter.format.Format._get_align_properties 57 4 7.017% ['xlsx_fuzzer']
xlsxwriter.worksheet.Worksheet._write 42 0 0.0% []
xlsxwriter.worksheet.Worksheet._prepare_formula 166 39 23.49% ['xlsx_fuzzer']
xlsxwriter.worksheet.Worksheet._write_rich_string 57 0 0.0% []
xlsxwriter.worksheet.Worksheet.autofit 63 0 0.0% []
xlsxwriter.worksheet.Worksheet.data_validation 87 0 0.0% []
xlsxwriter.worksheet.Worksheet.conditional_format 205 0 0.0% []
xlsxwriter.worksheet.Worksheet.add_table 161 0 0.0% []
xlsxwriter.worksheet.Worksheet.add_sparkline 87 0 0.0% []
xlsxwriter.worksheet.Worksheet.set_header 43 0 0.0% []
xlsxwriter.worksheet.Worksheet.set_footer 43 0 0.0% []
xlsxwriter.worksheet.Worksheet._parse_filter_tokens 33 0 0.0% []
xlsxwriter.worksheet.Worksheet._prepare_image 37 0 0.0% []
xlsxwriter.worksheet.Worksheet._prepare_shape 35 0 0.0% []
xlsxwriter.worksheet.Worksheet._position_object_pixels 41 0 0.0% []
xlsxwriter.worksheet.Worksheet._write_font 35 0 0.0% []
xlsxwriter.worksheet.Worksheet._set_icon_props 36 0 0.0% []
xlsxwriter.worksheet.Worksheet._write_sheet_view 34 15 44.11% ['xlsx_fuzzer']
xlsxwriter.worksheet.Worksheet._write_col_info 32 0 0.0% []
xlsxwriter.worksheet.Worksheet._write_page_setup 32 3 9.375% ['xlsx_fuzzer']
xlsxwriter.worksheet.Worksheet._write_cell 63 25 39.68% ['xlsx_fuzzer']
xlsxwriter.worksheet.Worksheet._write_sheet_protection 41 3 7.317% ['xlsx_fuzzer']
xlsxwriter.worksheet.Worksheet._write_data_validation 46 0 0.0% []
xlsxwriter.worksheet.Worksheet._write_cf_rule 68 0 0.0% []
xlsxwriter.worksheet.Worksheet._write_freeze_panes 36 0 0.0% []
xlsxwriter.worksheet.Worksheet._write_split_panes 42 0 0.0% []
xlsxwriter.worksheet.Worksheet._write_sparkline_group 43 0 0.0% []
xlsxwriter.worksheet.Worksheet._write_ignored_errors 31 2 6.451% ['xlsx_fuzzer']
xlsxwriter.chart.Chart.__init__ 67 0 0.0% []
xlsxwriter.chart.Chart.add_series 54 0 0.0% []
xlsxwriter.chart.Chart._convert_axis_args 46 0 0.0% []
xlsxwriter.chart.Chart._get_labels_properties 63 0 0.0% []
xlsxwriter.chart.Chart._write_cat_axis 39 0 0.0% []
xlsxwriter.chart.Chart._write_val_axis 35 0 0.0% []
xlsxwriter.chart.Chart._write_cat_val_axis 35 0 0.0% []
xlsxwriter.chart.Chart._write_date_axis 41 0 0.0% []
xlsxwriter.chart.Chart._write_custom_labels 32 0 0.0% []
xlsxwriter.utility.quote_sheetname 31 0 0.0% []
xlsxwriter.shape.Shape._get_gradient_properties 41 0 0.0% []
xlsxwriter.color.Color._attributes 52 0 0.0% []
xlsxwriter.drawing.Drawing._write_tx_body 64 0 0.0% []
xlsxwriter.comments.CommentType._set_user_options 50 0 0.0% []
xlsxwriter.styles.Styles._write_xf 39 21 53.84% ['xlsx_fuzzer']
xlsxwriter.image.Image._get_image_properties 40 0 0.0% []
xlsxwriter.image.Image._process_jpg 32 0 0.0% []
xlsxwriter.url.Url._parse_url 42 0 0.0% []

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
[] []
atheris [] []
xlsxwriter.comments [] []
xlsxwriter.workbook [] []
xlsxwriter.relationships [] []
shutil [] []
zipfile [] []
time [] []
xlsxwriter.core [] []
os [] []
copy [] []
xlsxwriter.custom [] []
xlsxwriter.url [] []
xlsxwriter.feature_property_bag [] []
xlsxwriter.contenttypes [] []
xlsxwriter.image [] []
xlsxwriter.chart_area [] []
[] []
xlsxwriter.chart_column [] []
xlsxwriter.chart_scatter [] []
xlsxwriter.shape [] []
xlsxwriter.rich_value_types [] []
xlsxwriter.rich_value [] []
xlsxwriter.app [] []
io [] []
xlsxwriter.exceptions [] []
tempfile [] []
xlsxwriter.chart_radar [] []
xlsxwriter.chart_doughnut [] []
xlsxwriter.format [] []
warnings [] []
re [] []
fuzz_helpers [] []
xlsxwriter.packager [] []
xlsxwriter.chart [] []
xlsxwriter.table [] []
xlsxwriter.drawing [] []
functools [] []
xlsxwriter.chart_stock [] []
xlsxwriter.color [] []
xlsxwriter [] []
xlsxwriter.sharedstrings [] []
xlsxwriter.chart_bar [] []
struct [] []
xlsxwriter.xmlwriter [] []
math [] []
hashlib [] []
xlsxwriter.worksheet [] []
operator [] []
xlsxwriter.rich_value_structure [] []
xlsxwriter.theme [] []
xlsxwriter.utility [] []
xlsxwriter.rich_value_rel [] []
...XlsxWriter.dev.fuzzing.xlsx_fuzzer ['xlsx_fuzzer'] []
xlsxwriter.chart_pie [] []
xlsxwriter.vml [] []
datetime [] []
xlsxwriter.styles [] []
xlsxwriter.chart_line [] []
xlsxwriter.chartsheet [] []
xlsxwriter.metadata [] []
collections [] []

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
xlsx_fuzzer fuzzerLogFile-xlsx_fuzzer.data fuzzerLogFile-xlsx_fuzzer.data.yaml all_cov.json