C++ UML diagram generator based on Clang

clang-uml is an automatic C++ to UML class, sequence, package and include diagram generator, driven by YAML configuration files. The main idea behind the project is to easily maintain up-to-date diagrams within a code-base or document legacy code. The configuration file or files for clang-uml define the type and contents of each generated diagram. Currently, the diagrams are generated in PlantUML format.

clang-uml currently supports C++ up to version 17.

Features

Main features supported so far include:

• Class diagram generation
  • Basic class properties and methods including visibility
  • Class relationships including associations, aggregations, dependencies and friendship
  • Template instantiation relationships
  • Relationship inference from C++ containers and smart pointers
  • Diagram content filtering based on namespaces, elements and relationships
  • Optional package generation from namespaces
  • Interactive links to online code to classes, methods and class fields in SVG diagrams
• Sequence diagram generation
  • Generation of sequence diagram from specific method or function
  • Generation of loop and conditional statements
  • Generation of switch statements
  • Generation of try/catch blocks
  • Handling of template code including constexpr conditionals
  • Handling of lambda expressions
  • Interactive links to online code to classes and call expressions
• Package diagram generation
  • Generation of package diagram based on C++ namespaces
  • Interactive links to online code to packages
• Include graph diagram generation
  • Show include graph for selected files

To see what clang-uml can do so far, checkout the diagrams generated for unit test cases here and examples in clang-uml-examples repository.

More comprehensive documentation can be found here.

Installation

Installation instructions for Linux, macos and Windows can be found here.

Usage

Generating compile commands database

clang-uml requires an up-to-date compile_commands.json file, containing the list of commands used for compiling the source code. Nowadays, this file can be generated rather easily using multiple methods:

• For CMake projects, simply invoke the cmake command as cmake -DCMAKE_EXPORT_COMPILE_COMMANDS=ON ...
• For Make projects checkout compiledb or Bear
• For Boost-based projects try commands_to_compilation_database
• For SCons, invoke compilation_db tool (requires SCons > 4.0.0)
• For Microsoft Visual Studio projects try Clang Power Tools

Invocation

By default, config-uml will assume that the configuration file .clang-uml and compilation database compile_commands.json files are in the current directory, so if they are in the top level directory of a project, simply run:

clang-uml

The output path for diagrams, as well as alternative location of compilation database can be specified in .clang-uml configuration file.

For other options checkout help:

clang-uml --help

Configuration file format and examples

Configuration files are written in YAML, and provide a list of diagrams which should be generated by clang-uml. Basic example is as follows:

compilation_database_dir: .
output_directory: puml
diagrams:
  myproject_class:
    type: class
    glob:
      - src/*.cc
    using_namespace:
      - myproject
    include:
      namespaces:
        - myproject
    exclude:
      namespaces:
        - myproject::detail
    plantuml:
      after:
        - 'note left of {{ alias("MyProjectMain") }}: Main class of myproject library.'

See here for detailed configuration file reference guide.

Examples

To see what clang-uml can do, checkout the test cases documentation here.

In order to see diagrams for the clang-uml itself, based on its own config run the following:

make clanguml_diagrams

and checkout the SVG diagrams in docs/diagrams folder.

Class diagrams

Example

The following C++ code:

template <typename T, typename P> struct A {
    T t;
    P p;
};

struct B {
    std::string value;
};

template <typename T> using AString = A<T, std::string>;
template <typename T> using AStringPtr = A<T, std::unique_ptr<std::string>>;

template <typename T>
using PairPairBA = std::pair<std::pair<B, A<long, T>>, long>;

template <class T> using VectorPtr = std::unique_ptr<std::vector<T>>;
template <class T> using APtr = std::unique_ptr<A<double, T>>;
template <class T> using ASharedPtr = std::shared_ptr<A<double, T>>;
template <class T, class U>
using AAPtr = std::unique_ptr<std::pair<A<double, T>, A<long, U>>>;

template <typename T> using SimpleCallback = std::function<void(T, int)>;
template <typename... T> using GenericCallback = std::function<void(T..., int)>;
using VoidCallback = GenericCallback<void *>;

using BVector = std::vector<B>;
using BVector2 = BVector;

using AIntString = AString<int>;
using ACharString = AString<char>;
using AWCharString = AString<wchar_t>;
using AStringString = AString<std::string>;
using BStringString = AStringString;

class R {
    PairPairBA<bool> bapair;

    APtr<bool> abool;
    AAPtr<bool, float> aboolfloat;
    ASharedPtr<float> afloat;
    A<bool, std::string> boolstring;
    AStringPtr<float> floatstring;
    AIntString intstring;
    AStringString stringstring;
    BStringString bstringstring;

protected:
    BVector bs;

public:
    BVector2 bs2;
    SimpleCallback<ACharString> cb;
    GenericCallback<AWCharString> gcb;
    VoidCallback vcb;
    VectorPtr<B> vps;
};

generates the following diagram (via PlantUML):

Open the raw image here, and checkout the hover tooltips and hyperlinks to classes and methods.

Sequence diagrams

Example

The following C++ code:

#include <atomic>
#include <functional>
#include <iostream>
#include <memory>
#include <string>

namespace clanguml {
namespace t20029 {
std::string encode_b64(std::string &&content) { return std::move(content); }

template <typename T> class Encoder : public T {
public:
    bool send(std::string &&msg)
    {
        return T::send(std::move(encode(std::move(msg))));
    }

protected:
    std::string encode(std::string &&msg) { return encode_b64(std::move(msg)); }
};

template <typename T> class Retrier : public T {
public:
    bool send(std::string &&msg)
    {
        std::string buffer{std::move(msg)};

        int retryCount = 5;

        while (retryCount--) {
            if (T::send(buffer))
                return true;
        }

        return false;
    }
};

class ConnectionPool {
public:
    void connect()
    {
        if (!is_connected_.load())
            connect_impl();
    }

    bool send(const std::string &msg) { return true; }

private:
    void connect_impl() { is_connected_ = true; }

    std::atomic<bool> is_connected_;
};

int tmain()
{
    auto pool = std::make_shared<Encoder<Retrier<ConnectionPool>>>();

    pool->connect();

    for (std::string line; std::getline(std::cin, line);) {
        if (!pool->send(std::move(line)))
            break;
    }

    return 0;
}
}
}

generates the following diagram (via PlantUML):

Package diagrams

Example

The following C++ code:

namespace clanguml {
namespace t30003 {

namespace ns1 {
namespace ns2_v1_0_0 {
class A {
};
}

namespace [[deprecated]] ns2_v0_9_0 {
class A {
};
}

namespace {
class Anon final {
};
}
}

namespace [[deprecated]] ns3 {

namespace ns1::ns2 {
class Anon : public t30003::ns1::ns2_v1_0_0::A {
};
}

class B : public ns1::ns2::Anon {
};
}
}
}

generates the following diagram (via PlantUML):

Include diagrams

In case you're looking for a simpler tool to visualize and analyze include graphs checkout my other tool - clang-include-graph

Example

The following C++ code structure:

tests/t40001
├── include
│   ├── lib1
│   │   └── lib1.h
│   └── t40001_include1.h
└── src
    └── t40001.cc

generates the following diagram (via PlantUML) based on include directives in the code:

Default mappings

UML	PlantUML
Inheritance
Association
Dependency
Aggregation
Composition
Template specialization/instantiation
Nesting (inner class/enum)
Include (local)
Include (system)

Diagram content filtering

For typical code bases, generating a single diagram from entire code or even a single namespace can be too big to be useful, e.g. as part of documentation. clang-uml allows specifying content to be included and excluded from each diagram using simple YAML configuration:

include:
  # Include only elements from these namespaces
  namespaces:
    - clanguml::common
    - clanguml::config
  # Include all subclasses of ClassA (including ClassA)
  subclasses:
    - clanguml::common::ClassA
  # and specializations of template Class<T> (including Class<T>)
  specializations:
    - clanguml::common::ClassT<T>
  # and all classes depending on Class D
  dependants:
    - clanguml::common::ClassD
  # and all dependencies of ClassE
  dependencies:
    - clanguml::common::ClassE
  # and classes in direct relation to ClassB (including ClassB)
  context:
    - clanguml::common::ClassB
  # Include only inheritance relationships
  relationships:
    - inheritance
exclude:
  # Exclude all elements from detail namespace
  namespaces:
    - clanguml::common::detail
  # and also exclude ClassF
  elements:
    - clanguml::common::ClassF

More details on this can be found in the diagram filters documentation section.

Test cases

The build-in test cases used for unit testing of the clang-uml, can be browsed here.

Acknowledgements

This project relies on the following great tools:

• Clang LibTooling - a C++ library for creating tools based on Clang
• PlantUML - language and diagram for generating UML diagrams
• Catch2 - C++ unit test framework
• glob - Unix style path expansion for C++
• CLI11 - command line parser for C++
• inja - a template engine for modern C++

Contributing

If you would like to contribute to the project, please check out contributing guidelines.

LICENSE

Copyright 2021-present Bartek Kryza <[email protected]>

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

  http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.