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

Table of contents

Project overview: htslib
High level conclusions
Reachability and coverage overview
Fuzzers overview
Project functions overview
Fuzzer details
Fuzzer: hts_open_fuzzer
Call tree
Analyses and suggestions
Optimal target analysis
Remaining optimal interesting functions
All functions overview
Fuzz engine guidance
/src/htslib/test/fuzz/hts_open_fuzzer.c
Dictionary
Fuzzer function priority
Runtime coverage analysis
Files and Directories in report
Files in report
Directories in report
Metadata section
Report generation date: 2026-07-16

Project overview: htslib

High level conclusions

Reachability and coverage overview

Functions statically reachable by fuzzers
59.0%
993 / 1694
Cyclomatic complexity statically reachable by fuzzers
65.0%
11283 / 17281
Runtime code coverage of functions
0.0%
0 / 1694

Fuzzers overview

Fuzzer Fuzzer filename Functions Reached Functions unreached Fuzzer depth Files reached Basic blocks reached Cyclomatic complexity Details
hts_open_fuzzer /src/htslib/test/fuzz/hts_open_fuzzer.c 1117 740 19 73 29937 11532 hts_open_fuzzer.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: hts_open_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 project has no code coverage. Will not display blockers as blockers depend on code coverage.

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
tbx_itr_regarray /src/htslib/tbx.c 3 ['N/A', 'N/A', 'int'] 9 0 63 9 4 148 0 1023 483
vhopen_s3 /src/htslib/hfile_s3.c 3 ['N/A', 'N/A', 'N/A'] 13 0 23 3 2 129 0 666 464
vhopen_libcurl /src/htslib/hfile_libcurl.c 3 ['N/A', 'N/A', 'N/A'] 14 0 54 9 4 163 0 880 382
bam_mplp_auto /src/htslib/sam.c 5 ['N/A', 'N/A', 'N/A', 'N/A', 'N/A'] 8 0 65 10 4 38 0 343 282
bcf_index_build /src/htslib/vcf.c 2 ['N/A', 'int'] 27 0 18 3 2 975 0 9696 207
rans_uncompress_O1_32x16_avx2 /src/htslib/htscodecs/htscodecs/rANS_static32x16pr_avx2.c 4 ['N/A', 'int', 'N/A', 'int'] 4 0 4552 103 35 24 0 185 126
bcf_hdr_subset /src/htslib/vcf.c 4 ['N/A', 'int', 'N/A', 'N/A'] 11 0 376 49 18 105 0 816 118
rans_compress_O1_32x16_avx512 /src/htslib/htscodecs/htscodecs/rANS_static32x16pr_avx512.c 4 ['N/A', 'int', 'N/A', 'N/A'] 8 0 1822 92 29 35 0 223 117
sam_hdr_remove_lines /src/htslib/header.c 4 ['N/A', 'N/A', 'N/A', 'N/A'] 13 0 352 59 24 100 0 823 114
bcf_itr_querys1 /src/htslib/vcf.c 3 ['N/A', 'N/A', 'N/A'] 12 0 21 3 2 163 0 1158 95

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

Functions statically reachable by fuzzers
72.0%
1216 / 1694
Cyclomatic complexity statically reachable by fuzzers
79.0%
13615 / 17281

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.

/src/htslib/test/fuzz/hts_open_fuzzer.c

Dictionary

Use this with the libFuzzer -dict=DICT.file flag


Runtime coverage analysis

No runtime coverage data was found

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/htslib/htscodecs/htscodecs/rle.c ['hts_open_fuzzer'] []
/src/htslib/htscodecs/htscodecs/rANS_static32x16pr_avx512.c [] []
/src/htslib/kstring.c ['hts_open_fuzzer'] []
/src/htslib/cram/cram_codecs.c ['hts_open_fuzzer'] []
/src/htslib/hfile.c ['hts_open_fuzzer'] []
/src/htslib/./htslib/vcf.h ['hts_open_fuzzer'] []
/src/htslib/cram/cram_decode.c ['hts_open_fuzzer'] []
/src/htslib/./htslib/hfile.h ['hts_open_fuzzer'] []
/src/htslib/htscodecs/htscodecs/rANS_static.c ['hts_open_fuzzer'] []
/src/htslib/htscodecs/htscodecs/utils.c ['hts_open_fuzzer'] []
/src/htslib/htscodecs/htscodecs/rANS_static4x16pr.c ['hts_open_fuzzer'] []
/src/htslib/cram/cram_io.h ['hts_open_fuzzer'] []
/src/htslib/./bgzf_internal.h ['hts_open_fuzzer'] []
/src/htslib/hfile_gcs.c ['hts_open_fuzzer'] []
/src/htslib/cram/cram_index.c ['hts_open_fuzzer'] []
/src/htslib/hts.c ['hts_open_fuzzer'] []
/src/htslib/./cram/../htslib/khash.h ['hts_open_fuzzer'] []
/src/htslib/./htslib/hts.h ['hts_open_fuzzer'] []
/src/htslib/cram/cram_io.c ['hts_open_fuzzer'] []
/src/htslib/hts_expr.c ['hts_open_fuzzer'] []
/src/htslib/cram/mFILE.c ['hts_open_fuzzer'] []
/src/htslib/./hts_time_funcs.h [] []
/src/htslib/cram/../textutils_internal.h ['hts_open_fuzzer'] []
/src/htslib/cram/string_alloc.c ['hts_open_fuzzer'] []
/src/htslib/cram/../htslib/kstring.h ['hts_open_fuzzer'] []
/src/htslib/htscodecs/htscodecs/c_simple_model.h ['hts_open_fuzzer'] []
/src/htslib/htscodecs/htscodecs/fqzcomp_qual.c ['hts_open_fuzzer'] []
/src/htslib/cram/../sam_internal.h ['hts_open_fuzzer'] []
/src/htslib/./htslib/hts_alloc.h ['hts_open_fuzzer'] []
/src/htslib/cram/pooled_alloc.c ['hts_open_fuzzer'] []
/src/htslib/./textutils_internal.h ['hts_open_fuzzer'] []
/src/htslib/./htslib/khash.h ['hts_open_fuzzer'] []
/src/htslib/md5.c ['hts_open_fuzzer'] []
/usr/local/lib/clang/22/include/cpuid.h ['hts_open_fuzzer'] []
/src/htslib/cram/../header.h ['hts_open_fuzzer'] []
/src/htslib/cram/../htslib/sam.h ['hts_open_fuzzer'] []
/src/htslib/faidx.c ['hts_open_fuzzer'] []
/src/htslib/./hts_internal.h ['hts_open_fuzzer'] []
/src/htslib/cram/open_trace_file.c ['hts_open_fuzzer'] []
/src/htslib/hfile_libcurl.c ['hts_open_fuzzer'] []
/src/htslib/htscodecs/htscodecs/pooled_alloc.h ['hts_open_fuzzer'] []
/src/htslib/./htslib/hts_defs.h [] []
/src/htslib/cram/cram_encode.c ['hts_open_fuzzer'] []
/src/htslib/hfile_s3.c ['hts_open_fuzzer'] []
/src/htslib/htscodecs/htscodecs/htscodecs.c [] []
/src/htslib/htscodecs/htscodecs/tokenise_name3.c ['hts_open_fuzzer'] []
/src/htslib/cram/cram_codecs.h [] []
/src/htslib/cram/../htslib/hts_alloc.h ['hts_open_fuzzer'] []
/src/htslib/thread_pool.c ['hts_open_fuzzer'] []
/src/htslib/./sam_internal.h ['hts_open_fuzzer'] []
/src/htslib/htscodecs/htscodecs/varint.h ['hts_open_fuzzer'] []
/src/htslib/htscodecs/htscodecs/c_range_coder.h ['hts_open_fuzzer'] []
/src/htslib/textutils.c ['hts_open_fuzzer'] []
/src/htslib/sam_mods.c [] []
/src/htslib/cram/cram_stats.c ['hts_open_fuzzer'] []
/src/htslib/htscodecs/htscodecs/rANS_byte.h ['hts_open_fuzzer'] []
/src/htslib/test/fuzz/hts_open_fuzzer.c ['hts_open_fuzzer'] []
/src/htslib/./htslib/sam.h ['hts_open_fuzzer'] []
/src/htslib/htscodecs/htscodecs/rANS_static32x16pr.c [] []
/src/htslib/htscodecs/htscodecs/arith_dynamic.c ['hts_open_fuzzer'] []
/src/htslib/multipart.c ['hts_open_fuzzer'] []
/src/htslib/vcf.c ['hts_open_fuzzer'] []
/src/htslib/sam.c ['hts_open_fuzzer'] []
/src/htslib/region.c [] []
/src/htslib/cram/../htslib/hfile.h ['hts_open_fuzzer'] []
/src/htslib/./htslib/bgzf.h ['hts_open_fuzzer'] []
/src/htslib/htscodecs/htscodecs/pack.c ['hts_open_fuzzer'] []
/src/htslib/header.c ['hts_open_fuzzer'] []
/src/htslib/htscodecs/htscodecs/rANS_static32x16pr_sse4.c [] []
/src/htslib/cram/cram_structs.h ['hts_open_fuzzer'] []
/src/htslib/./header.h ['hts_open_fuzzer'] []
/src/htslib/tbx.c ['hts_open_fuzzer'] []
/src/htslib/simd.c [] []
/src/htslib/cram/../htslib/hts_endian.h ['hts_open_fuzzer'] []
/src/htslib/./htslib/khash_str2int.h [] []
/src/htslib/./htslib/hts_endian.h ['hts_open_fuzzer'] []
/src/htslib/htscodecs/htscodecs/utils.h ['hts_open_fuzzer'] []
/src/htslib/htscodecs/htscodecs/rANS_static32x16pr_avx2.c [] []
/src/htslib/./htslib/hts_expr.h ['hts_open_fuzzer'] []
/src/htslib/./cram/cram_io.h ['hts_open_fuzzer'] []
/src/htslib/htscodecs/htscodecs/rANS_word.h [] []
/src/htslib/htscodecs/htscodecs/rANS_static16_int.h [] []
/src/htslib/bgzf.c ['hts_open_fuzzer'] []
/src/htslib/./htslib/kstring.h ['hts_open_fuzzer'] []

Directories in report

Directory
/src/htslib/./htslib/
/src/htslib/cram/../htslib/
/src/htslib/test/fuzz/
/src/htslib/cram/../
/src/htslib/
/src/htslib/./cram/
/src/htslib/htscodecs/htscodecs/
/src/htslib/cram/
/usr/local/lib/clang/22/include/
/src/htslib/./cram/../htslib/
/src/htslib/./

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
hts_open_fuzzer fuzzerLogFile-0-zcHQcaQYio.data fuzzerLogFile-0-zcHQcaQYio.data.yaml