Lizard
Lizard is an extensible Cyclomatic Complexity Analyzer for many programming languages including C/C++ (doesn’t require all the header files or Java imports). It also does copy-paste detection (code clone detection/code duplicate detection) and many other forms of static code analysis.
A list of supported languages:
C# (C Sharp)
C/C++ (works with C++14)
Erlang
Fortran
GDScript
Golang
Java
JavaScript (With ES6 and JSX)
Kotlin
Lua
Objective-C
Perl
PHP
PL/SQL
Python
R
Ruby
Rust
Scala
Solidity
Structured Text (St)
Swift
TTCN-3
TypeScript (With TSX)
VueJS
Zig
By default lizard will search for any source code that it knows and mix all the results together. This might not be what you want. You can use the “-l” option to select language(s).
It counts
the nloc (lines of code without comments),
CCN (cyclomatic complexity number),
token count of functions.
parameter count of functions.
You can set limitation for CCN (-C), the number of parameters (-a). Functions that exceed these limitations will generate warnings. The exit code of lizard will be none-Zero if there are warnings.
This tool actually calculates how complex the code ‘looks’ rather than how complex the code really ‘is’. People will need this tool because it’s often very hard to get all the included folders and files right when they are complicated. But we don’t really need that kind of accuracy for cyclomatic complexity.
It requires python3.8 or above (early versions are not verified).
Installation
lizard.py can be used as a stand alone Python script, most functionalities are there. You can always use it without any installation. To acquire all the functionalities of lizard, you will need a proper install.
python lizard.py
If you want a proper install:
[sudo] pip install lizard
Or if you’ve got the source:
[sudo] python setup.py install --prefix=/path/to/installation/directory/
Usage
lizard [options] [PATH or FILE] [PATH] ...
Run for the code under current folder (recursively):
lizard
Exclude anything in the tests folder:
lizard mySource/ -x"./tests/*"
Use .gitignore file:
lizard mySource/
If there is a .gitignore file in the given path, lizard will automatically use it as an additional filter to exclude files that match the gitignore patterns. This is useful when you want to analyze only the tracked files in your git repository. To analyze all discovered source files regardless of .gitignore, use –no-gitignore:
lizard --no-gitignore mySource/
Options
-h, --help show this help message and exit
--version show program's version number and exit
-l LANGUAGES, --languages LANGUAGES
List the programming languages you want to analyze. if left empty, it'll
search for all languages it knows. `lizard -l cpp -l java`searches for
C++ and Java code. The available languages are: cpp, java, csharp,
javascript, python, objectivec, ttcn, ruby, php, swift, scala, GDScript,
go, lua, rust, typescript, plsql
-V, --verbose Output in verbose mode (long function name)
-C CCN, --CCN CCN Threshold for cyclomatic complexity number warning. The default value is
15. Functions with CCN bigger than it will generate warning
-f INPUT_FILE, --input_file INPUT_FILE
get a list of filenames from the given file
-o OUTPUT_FILE, --output_file OUTPUT_FILE
Output file. The output format is inferred from the file extension (e.g.
.html), unless it is explicitly specified (e.g. using --xml).
-L LENGTH, --length LENGTH
Threshold for maximum function length warning. The default value is 1000.
Functions length bigger than it will generate warning
-a ARGUMENTS, --arguments ARGUMENTS
Limit for number of parameters
-w, --warnings_only Show warnings only, using clang/gcc's warning format for printing
warnings. http://clang.llvm.org/docs/UsersManual.html#cmdoption-
fdiagnostics-format
--warning-msvs Show warnings only, using Visual Studio's warning format for printing
warnings. https://msdn.microsoft.com/en-us/library/yxkt8b26.aspx
-i NUMBER, --ignore_warnings NUMBER
If the number of warnings is equal or less than the number, the tool will
exit normally; otherwise, it will generate error. If the number is
negative, the tool exits normally regardless of the number of warnings.
Useful in makefile for legacy code.
-x EXCLUDE, --exclude EXCLUDE
Exclude files that match the pattern. * matches everything, ? matches any
single character, "./folder/*" exclude everything in the folder
recursively. Multiple patterns can be specified. Don't forget to add ""
around the pattern.
--no-gitignore Do not use .gitignore files to exclude files.
-t WORKING_THREADS, --working_threads WORKING_THREADS
number of working threads. The default value is 1. Using a bigger number
can fully utilize the CPU and often faster.
-X, --xml Generate XML in cppncss style instead of the tabular output. Useful to
generate report in Jenkins server
--csv Generate CSV output as a transform of the default output
-H, --html Output HTML report with interactive DataTables (sortable, searchable, filterable)
--checkstyle Generate Checkstyle XML output for integration with Jenkins and other tools
-m, --modified Calculate modified cyclomatic complexity number , which count a
switch/case with multiple cases as one CCN.
-E EXTENSIONS, --extension EXTENSIONS
User the extensions. The available extensions are: -Ecpre: it will ignore
code in the #else branch. -Ewordcount: count word frequencies and
generate tag cloud. -Eoutside: include the global code as one function.
-EIgnoreAssert: to ignore all code in assert. -ENS: count nested control
structures. -Ehalstead: compute Halstead complexity metrics. -Ecognitive:
compute Cognitive Complexity (SonarSource).
-s SORTING, --sort SORTING
Sort the warning with field. The field can be nloc,
cyclomatic_complexity, token_count, parameter_count, etc. Or an customized field.
-T THRESHOLDS, --Threshold THRESHOLDS
Set the limit for a field. The field can be nloc, cyclomatic_complexity,
token_count, parameter_count, etc. Or an customized file. Lizard will
report warning if a function exceed the limit
-W WHITELIST, --whitelist WHITELIST
The path and file name to the whitelist file. It's './whitelizard.txt' by
default. Find more information in README.
Example use
Analyze a folder recursively: lizard mahjong_game/src
==============================================================
NLOC CCN token param function@line@file
--------------------------------------------------------------
10 2 29 2 start_new_player@26@./html_game.c
...
6 1 3 0 set_shutdown_flag@449@./httpd.c
24 3 61 1 server_main@454@./httpd.c
--------------------------------------------------------------
2 file analyzed.
==============================================================
LOC Avg.NLOC AvgCCN Avg.ttoken function_cnt file
--------------------------------------------------------------
191 15 3 51 12 ./html_game.c
363 24 4 86 15 ./httpd.c
======================================
!!!! Warnings (CCN > 15) !!!!
======================================
66 19 247 1 accept_request@64@./httpd.c
=================================================================================
Total NLOC Avg.NLOC Avg CCN Avg token Fun Cnt Warning cnt Fun Rt NLOC Rt
--------------------------------------------------------------------------------
554 20 4.07 71.15 27 1 0.04 0.12
Warnings only (in clang/gcc formation):lizard -w mahjong_game
./src/html_ui/httpd.c:64: warning: accept_request has 19 CCN and 1 params (66 NLOC, 247 tokens) ./src/mahjong_game/mj_table.c:109: warning: mj_table_update_state has 20 CCN and 1 params (72 NLOC, 255 tokens)
Set warning threshold for any field:lizard -T nloc=25
The option -Tcyclomatic_complexity=10 is equal to -C10. The option -Tlength=10 is equal to -L10. The option -Tparameter_count=10 is equal to -a10.
You can also do -Tnloc=10 to set the limit of the NLOC. Any function that has NLOC greater than 10 will generate a warning.
Generated code
Lizard has a simple solution with generated code. Any code in a source file that is following a comment containing “GENERATED CODE” will be ignored completely. The ignored code will not generate any data, except the file counting.
Code Duplicate Detector
lizard -Eduplicate <path to your code>
Generate A Tag Cloud For Your Code
You can generate a “Tag cloud” of your code by the following command. It counts the identifiers in your code (ignoring the comments).
lizard -EWordCount <path to your code>
Cognitive Complexity
Cognitive Complexity (SonarSource, G. Ann Campbell) measures how hard a function is to understand rather than how many paths it has: a switch counts one no matter how many cases it has, a sequence of like logical operators (a && b && c) counts one, and control structures cost more the deeper they are nested. Enable it as an extension; it adds a CogC column, a --CogC warning threshold (15 by default) and a cognitive_complexity field usable with -s and -T:
lizard -Ecognitive <path to your code> lizard -Ecognitive --CogC 25 -s cognitive_complexity <path to your code>
Nesting is followed for brace-delimited languages (C/C++, Java, C#, JavaScript/TypeScript, Go, Rust, Kotlin, Swift, PHP, …) and for Python; for the other languages the increments are counted without the nesting penalty. C preprocessor conditionals are not counted.
Using lizard as Python module
You can also use lizard as a Python module in your code:
>>> import lizard
>>> i = lizard.analyze_file("../cpputest/tests/AllTests.cpp")
>>> print i.__dict__
{'nloc': 9, 'function_list': [<lizard.FunctionInfo object at 0x10bf7af10>], 'filename': '../cpputest/tests/AllTests.cpp'}
>>> print i.function_list[0].__dict__
{'cyclomatic_complexity': 1, 'token_count': 22, 'name': 'main', 'parameter_count': 2, 'nloc': 3, 'long_name': 'main( int ac , const char ** av )', 'start_line': 30}You can also use source code string instead of file. But you need to provide a file name (to identify the language).
>>> i = lizard.analyze_file.analyze_source_code("AllTests.cpp", "int foo(){}")Whitelist
If for some reason you would like to ignore the warnings, you can use the whitelist. Add ‘whitelizard.txt’ to the current folder (or use -W to point to the whitelist file), then the functions defined in the file will be ignored. Please notice that if you assign the file pathname, it needs to be exactly the same relative path as Lizard to find the file. An easy way to get the file pathname is to copy it from the Lizard warning output. This is an example whitelist:
#whitelizard.txt #The file name can only be whitelizard.txt and put it in the current folder. #You may have commented lines begin with #. function_name1, function_name2 # list function names in multiple lines or split with comma. file/path/name:function1, function2 # you can also specify the filename
Options in Comments
You can use options in the comments of the source code to change the behavior of lizard. There are two types of forgiveness comments:
Function forgiveness: Put “#lizard forgives” inside a function or before a function to suppress warnings for that function.
int foo() {
// #lizard forgives
...
}
Selective forgiveness: Use "#lizard forgives(metric1, metric2)" to forgive only specific metrics (e.g. length, cyclomatic_complexity, parameter_count, nloc, token_count).
int foo() {
// #lizard forgives(length) // Forgive only length violations
...
}
Global code forgiveness: Put “#lizard forgive global” before global code to suppress warnings for all code outside of functions.
// #lizard forgive global
int global_var = 0;
if (condition) { // This complexity won't be counted
...
}
int foo() { // Functions are still counted normally
...
}
Limitations
Lizard requires syntactically correct code. Upon processing input with incorrect or unknown syntax:
Lizard guarantees to terminate eventually (i.e., no forever loops, hangs) without hard failures (e.g., exit, crash, exceptions).
There is a chance of a combination of the following soft failures:
omission
misinterpretation
improper analysis / tally
success (the code under consideration is not relevant, e.g., global macros in C)
This approach makes the Lizard implementation simpler and more focused with partial parsers for various languages. Developers of Lizard attempt to minimize the possibility of soft failures. Hard failures are bugs in Lizard code, while soft failures are trade-offs or potential bugs.
In addition to asserting the correct code, Lizard may choose not to deal with some advanced or complicated language features:
C/C++ digraphs and trigraphs are not recognized.
C/C++ preprocessing or macro expansion is not performed. For example, using macro instead of parentheses (or partial statements in macros) can confuse Lizard’s bracket stacks.
Some C++ complicated templates may cause confusion with matching angle brackets and processing less-than < or more-than > operators inside of template arguments.
Literatures Referring to Lizard
Lizard is often used in software related researches. If you used it to support your work, you may contact the lizard author to add your work in the following list.
Software Quality in the ATLAS experiment at CERN, which refers to Lizard as one of the tools, has been published in the Journal of Physics: http://iopscience.iop.org/article/10.1088/1742-6596/898/7/072011
S Martin-Haugh et al 2017 J. Phys.: Conf. Ser. 898 072011
Lizard is also used as a plugin for fastlane to help check code complexity and submit xml report to sonar.
How To Contribute
Contributions are welcome. Project-specific development rules are in AGENTS.md. Adding a language reader uses .agents/skills/lizard-language-support/.
AI lifecycle guidance is installed under .agents/skills/ and .claude/skills/.
1 maintainer
Metadata
1 maintainer
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