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

Table of contents

Project overview: netcdf
High level conclusions
Reachability and coverage overview
Fuzzers overview
Project functions overview
Fuzzer details
Fuzzer: fuzz_open
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_open.c
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: 2025-10-28

Project overview: netcdf

High level conclusions

Reachability and coverage overview

Functions statically reachable by fuzzers
8.0%
178 / 2242
Cyclomatic complexity statically reachable by fuzzers
11.0%
1554 / 14351
Runtime code coverage of functions
8.0%
187 / 2242

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_open fuzz/fuzz_open.c 211 2098 15 28 4127 1621 fuzz_open.c

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_open

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 0 714 73.3%
gold [1:9] 182 18.6%
yellow [10:29] 10 1.02%
greenyellow [30:49] 1 0.10%
lawngreen 50+ 67 6.87%
All colors 974 100

Fuzz blockers

The following nodes represent call sites where fuzz blockers occur.

Amount of callsites blocked Calltree index Parent function Callsite Largest blocked function
162 754 processuri call site: 00754 NCpathabsolute
161 482 rclocatepos call site: 00482 NC_getactives3profile
73 404 ncuriparse call site: 00404 NC_s3urlrebuild
35 332 ncuriparse call site: 00332 ensurequerylist
30 183 NC_aws_load_credentials call site: 00183 awsparse
29 71 unparsepath call site: 00071 NCgetkindname
28 371 ncbytescat call site: 00371 ensurefraglist
24 728 processuri call site: 00728 ncurifragmentparams
21 276 rcsearch call site: 00276 rccompile
16 238 NC_aws_load_credentials call site: 00238 freeprofile
12 214 nclistget call site: 00214 nclistset
12 312 ncuriparse call site: 00312 parselist

Runtime coverage analysis

Covered functions
188
Functions that are reachable but not covered
110
Reachable functions
211
Percentage of reachable functions covered
47.87%
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
fuzz/fuzz_open.c 1
libdispatch/dfile.c 3
liblib/nc_initialize.c 3
libdispatch/ddispatch.c 5
libdispatch/nclist.c 12
libdispatch/dpathmgr.c 11
libdispatch/dmissing.c 1
libdispatch/nclog.c 8
libdispatch/drc.c 17
libdispatch/ds3util.c 14
libdispatch/ncbytes.c 10
libdispatch/dutil.c 8
libdispatch/ncuri.c 25
libdispatch/dauth.c 1
libdispatch/doffsets.c 1
libsrc/nc3dispatch.c 2
libsrc4/nc4dispatch.c 2
libdispatch/dplugins.c 3
libnczarr/zdispatch.c 2
libnczarr/zinternal.c 2
libnczarr/zprov.c 3
libnczarr/zarr.c 1
libdispatch/daux.c 3
libsrc4/nc4internal.c 2
libdispatch/dinfermodel.c 30
libdispatch/derror.c 1
libdispatch/nc.c 4
libdispatch/nclistmgr.c 4

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
NCZ_open /src/netcdf-c/libnczarr/zopen.c 7 ['N/A', 'int', 'int', 'N/A', 'N/A', 'N/A', 'int'] 20 0 123 24 9 376 0 3365 2431
NC3_put_vara /src/netcdf-c/build/libsrc/putget.c 6 ['int', 'int', 'N/A', 'N/A', 'N/A', 'int'] 11 0 501 75 29 355 0 2003 1743
NC3_get_vara /src/netcdf-c/build/libsrc/putget.c 6 ['int', 'int', 'N/A', 'N/A', 'N/A', 'int'] 6 0 485 73 28 304 0 1567 1404
NCZ_get_vara /src/netcdf-c/libnczarr/zvar.c 6 ['int', 'int', 'N/A', 'N/A', 'N/A', 'int'] 21 0 30 3 2 277 0 2370 723
NC3_def_var_fill /src/netcdf-c/libsrc/var.c 4 ['int', 'int', 'int', 'N/A'] 11 0 185 30 13 266 0 1529 645
NC3_open /src/netcdf-c/libsrc/nc3internal.c 7 ['N/A', 'int', 'int', 'N/A', 'N/A', 'N/A', 'int'] 10 0 193 32 11 140 0 770 490
NC3_get_att /src/netcdf-c/build/libsrc/attr.c 5 ['int', 'int', 'N/A', 'N/A', 'int'] 9 0 322 42 11 221 0 1088 293

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

Functions statically reachable by fuzzers
56.9%
1286 / 2242
Cyclomatic complexity statically reachable by fuzzers
64.0%
9251 / 14351

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_open.c

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=['processuri', 'rclocatepos', 'ncuriparse', 'NC_aws_load_credentials', 'unparsepath', 'ncbytescat', 'rcsearch']

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
NC_infermodel 127 43 33.85% ['fuzz_open']
processuri 54 19 35.18% ['fuzz_open']
NC_omodeinfer 58 14 24.13% ['fuzz_open']
openmagic 35 10 28.57% ['fuzz_open']
pathinit 43 21 48.83% ['fuzz_open']
parsepath 79 30 37.97% ['fuzz_open']
unparsepath 190 32 16.84% ['fuzz_open']
ncuriparse 201 55 27.36% ['fuzz_open']
memio_pad_length 31 7 22.58% ['fuzz_open']
NC_check_vlens 64 26 40.62% ['fuzz_open']
NC_calcsize 35 8 22.85% ['fuzz_open']
NC3_close 47 25 53.19% ['fuzz_open']
NC_var_shape 46 20 43.47% ['fuzz_open']

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/netcdf-c/libsrc4/nc4var.c [] []
/src/netcdf-c/libdispatch/nc.c ['fuzz_open'] ['fuzz_open']
/src/netcdf-c/libnczarr/zdim.c [] []
/src/netcdf-c/libnczarr/zcreate.c [] []
/src/netcdf-c/libdispatch/dattget.c [] []
/src/netcdf-c/libsrc/memio.c [] []
/src/netcdf-c/libsrc4/nc4grp.c [] []
/src/netcdf-c/libdispatch/nclistmgr.c ['fuzz_open'] ['fuzz_open']
/src/netcdf-c/libdispatch/ncexhash.c [] []
/src/netcdf-c/libdispatch/nclist.c ['fuzz_open'] ['fuzz_open']
/src/netcdf-c/libsrc/posixio.c [] []
/src/netcdf-c/libsrc/nc3internal.c [] []
/src/netcdf-c/libdispatch/drc.c ['fuzz_open'] ['fuzz_open']
/src/netcdf-c/libsrc4/ncfunc.c [] []
/src/netcdf-c/libnczarr/zattr.c [] []
/src/netcdf-c/build/libsrc/attr.c [] []
/src/netcdf-c/libnczarr/zodom.c [] []
/src/netcdf-c/libnczarr/zinternal.c ['fuzz_open'] ['fuzz_open']
/src/netcdf-c/libdispatch/dfile.c ['fuzz_open'] ['fuzz_open']
/src/netcdf-c/libdispatch/dutil.c ['fuzz_open'] ['fuzz_open']
/src/netcdf-c/libdispatch/dnotnc4.c [] []
/src/netcdf-c/libnczarr/zmap_file.c [] []
/src/netcdf-c/libsrc4/nc4dispatch.c ['fuzz_open'] ['fuzz_open']
/src/netcdf-c/libdispatch/ncxcache.c [] []
/src/netcdf-c/libsrc4/nc4type.c [] []
/src/netcdf-c/libnczarr/zclose.c [] []
/src/netcdf-c/libdispatch/dattinq.c [] []
/src/netcdf-c/libdispatch/ddim.c [] []
/src/netcdf-c/libsrc/ncio.c [] []
/src/netcdf-c/libnczarr/zxcache.c [] []
/src/netcdf-c/libdispatch/derror.c ['fuzz_open'] []
/src/netcdf-c/libnczarr/zsync.c [] []
/src/netcdf-c/libnczarr/zmap.c [] []
/src/netcdf-c/libdispatch/dvar.c [] []
/src/netcdf-c/libnczarr/zcvt.c [] []
/src/netcdf-c/libsrc/var.c [] []
/src/netcdf-c/build/libsrc/putget.c [] []
/src/netcdf-c/libnczarr/zprov.c ['fuzz_open'] ['fuzz_open']
/src/netcdf-c/libsrc/mmapio.c [] []
/src/netcdf-c/libsrc/nc3dispatch.c ['fuzz_open'] ['fuzz_open']
/src/netcdf-c/libdispatch/ddispatch.c ['fuzz_open'] ['fuzz_open']
/src/netcdf-c/libdispatch/dmissing.c ['fuzz_open'] ['fuzz_open']
/src/netcdf-c/libsrc/v1hpg.c [] []
/src/netcdf-c/libnczarr/zopen.c [] []
/src/netcdf-c/libsrc4/nc4attr.c [] []
/src/netcdf-c/libdispatch/dvarput.c [] []
/src/netcdf-c/libdispatch/dinstance.c [] []
/src/netcdf-c/libnczarr/zvar.c [] []
/src/netcdf-c/libdispatch/dcompound.c [] []
/src/netcdf-c/fuzz/fuzz_open.c ['fuzz_open'] ['fuzz_open']
/src/netcdf-c/libdispatch/dinfermodel.c ['fuzz_open'] ['fuzz_open']
/src/netcdf-c/libdispatch/daux.c ['fuzz_open'] ['fuzz_open']
/src/netcdf-c/build/libsrc/ncx.c [] []
/src/netcdf-c/libnczarr/zwalk.c [] []
/src/netcdf-c/libnczarr/zgrp.c [] []
/src/netcdf-c/libdispatch/dinstance_intern.c [] []
/src/netcdf-c/libdispatch/dvarget.c [] []
/src/netcdf-c/libdispatch/dattput.c [] []
/src/netcdf-c/libnczarr/zarr.c ['fuzz_open'] ['fuzz_open']
/src/netcdf-c/libdispatch/dpathmgr.c ['fuzz_open'] ['fuzz_open']
/src/netcdf-c/libdispatch/dstring.c [] []
/src/netcdf-c/libdispatch/dvarinq.c [] []
/src/netcdf-c/libnczarr/ztype.c [] []
/src/netcdf-c/libdispatch/dauth.c ['fuzz_open'] []
/src/netcdf-c/libdispatch/ncbytes.c ['fuzz_open'] ['fuzz_open']
/src/netcdf-c/libsrc/dim.c [] []
/src/netcdf-c/libnczarr/zfile.c [] []
/src/netcdf-c/libdispatch/ncjson.c [] []
/src/netcdf-c/libdispatch/nchashmap.c [] []
/src/netcdf-c/libdispatch/dtype.c [] []
/src/netcdf-c/libnczarr/zdispatch.c ['fuzz_open'] ['fuzz_open']
/src/netcdf-c/libnczarr/zdebug.c [] []
/src/netcdf-c/libdispatch/utf8proc.c [] []
/src/netcdf-c/libsrc4/nc4internal.c ['fuzz_open'] ['fuzz_open']
/src/netcdf-c/libsrc4/nc4dim.c [] []
/src/netcdf-c/libnczarr/zchunking.c [] []
/src/netcdf-c/libdispatch/nclog.c ['fuzz_open'] ['fuzz_open']
/src/netcdf-c/libdispatch/ds3util.c ['fuzz_open'] ['fuzz_open']
/src/netcdf-c/libdispatch/ncuri.c ['fuzz_open'] ['fuzz_open']
/src/netcdf-c/libdispatch/dplugins.c ['fuzz_open'] ['fuzz_open']
/src/netcdf-c/libdispatch/dutf8.c [] []
/src/netcdf-c/libdispatch/dcrc64.c [] []
/src/netcdf-c/libdispatch/dfilter.c [] []
/src/netcdf-c/liblib/nc_initialize.c ['fuzz_open'] ['fuzz_open']
/src/netcdf-c/libdispatch/ncindex.c [] []
/src/netcdf-c/libdispatch/doffsets.c ['fuzz_open'] ['fuzz_open']
/src/netcdf-c/libnczarr/zutil.c [] []
/src/netcdf-c/libdispatch/dgroup.c [] []

Directories in report

Directory
/src/netcdf-c/libdispatch/
/src/netcdf-c/libsrc/
/src/netcdf-c/libsrc4/
/src/netcdf-c/libnczarr/
/src/netcdf-c/fuzz/
/src/netcdf-c/liblib/
/src/netcdf-c/build/libsrc/

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_open fuzzerLogFile-0-zhtTziKtkz.data fuzzerLogFile-0-zhtTziKtkz.data.yaml fuzz_open.covreport