cxxbuild 1.6.0

CxxBuild is a python script to easily build C++ programs: just invoke 'cxxbuild' and it works!

cxxbuild / cxxdeps

cxxbuild (or "cplusplusbuild") is a python script to easily generate C/C++ build files for cmake and bazel.

• Version: cxxbuild version=1.6.0
• Installation: pip install cxxbuild (or pipx install cxxbuild for newer distributions)

For basic introduction, read the post: Using cxxbuild to easily build C++ project with tests and dependencies

We know it is very hard to start a C++ project and learn basics of build systems such as CMake and Bazel, and package managers like conan and vcpkg... so just type "cxxbuild" and be happy! But you MUST follow the canonical organization below:

project1/
        |
        | include/
        |        | package1/
        |                  | file1.h
        |                  | file2.hpp
        |                  | ...
        | src/
        |    | file1.cpp
        |    | file2.c
        |    | file_main.cpp
        |    | ...
        | cxxdeps.txt

The strongest point of this project is the cxxdeps.txt format, that allow easy specification of dependencies from different package managers (in similar style of python requirements.txt format)

To use it locally, just copy cxxbuild/cxxbuild.py file to your project and execute it: python3 cxxbuild.py help

Or, just install it from pip: pip install cxxbuild

Then, just run: cxxbuild help

From this point, we assume cxxbuild is installed in your system :)

Basic commands

cxxbuild has four main modes (three unimplemented, yet):

• build mode (default): just pass some root directory with files
• clean mode (unimplemented): will clean specific build files
• lint mode (unimplemented): will lint project files
• test mode (unimplemented): will run project tests

Running demos

• Demo 1 README: cxxbuild demo/project1
  • Dependencies: fmt, catch2, pthread:!windows, crypto:linux
• Demo 2 README: cxxbuild demo/project2
  • Dependencies: NONE
• Demo 3 README: cxxbuild demo/project3
  • Dependencies: fmt, catch2, pthread:!windows
• Demo 4 README: cxxbuild demo/project4 --c++20
  • Dependencies: catch2
• Demo 5 README: cxxbuild demo/project5
  • Dependencies (cmake-only): fmt, catch2
• Demo 6 README: cxxbuild demo/project6
  • Dependencies (cmake-only): optframe, absl (google abseil)

All of them support both CMake and Bazel build systems, for common platforms Linux, Windows and Mac.

Test summary for demos

• demo/project1: runs on linux, osx and windows* (bash only) - default c++17 (works with c++11 to c++23)
• demo/project2: runs on linux, osx and windows (bash and cmd) - default c++17 (works with c++11 to c++23)
• demo/project3: runs on linux, osx and windows* (bash only) - default c++17 (works with c++11 to c++23)
• demo/project4: runs on linux, osx and windows* (bash only) - requires minimum c++20

(*) Some limitations on windows/cmd are related to fmt dependency on cmake, not cxxbuild.

Running demo 1 (explained)

python3 cxxbuild/cxxbuild.py demo/project1

OR, after installation:

cxxbuild demo/project1

It will:

• read dependencies from cxxdeps.txt file, if available
• generate a CMakeLists.txt on project (backup your file if you already have one!)
• build with cmake+ninja (default) or any other provided build system

Generated binaries will be on demo/project1/build/

• demo1: binary with entrypoint (main) for demo (file: src/demo1.cpp)
• my_test: binary with unit tests (file: tests/my_test.cpp)

To clean it (since clean command is still unimplemented), just delete build/ folder.

Expected project organization

The tool cxxbuild assumes that:

• source code (.cpp, .cc, .c, etc) is located on a src/ folder
  • this can be changed with --src SRC_PATH option
• test code is located on a tests/ folder
  • this can be changed with --tests TEST_PATH option
• header only libraries are located on a include/ folder
  • this can be changed with --include INCLUDE_PATH option

The reason for src/ folder is:

1. enforces some "basic" project organization (I know many people don't like a src/ folder...)
2. recursively searching source files on root folder yields some issues, as build/ folder in same directory level becomes contaminated with external .cpp dependencies, thus requiring some clever exclusion algorithm

The reason for tests/ folder is:

1. enforces some "basic" project organization (I know many people don't like a tests/ folder...)
2. it is hard to distinguish between binary .cpp files and unit test files, unless some other "standard" is imposed, such as naming tests.cpp (but what about multiple tests then?)

The reason for include/ folder is:

1. this is classic organization, c'mon!!!
2. this is necessary to isolate header only library and make it easier for others to include them... if you don't want to offer a header only library, ok then, just put everything on src/ folder and that is fine!

These things can be easily changed, either manually on cxxbuild.py script, or by opening an issue and we discuss if some other option is really necessary... Note that this project does not aim to have many personalizations and complications, let's use KISS method!

Advantages and Drawbacks

Greatest advantage of this project is to easily describe dependencies on a cxxdeps.txt file.

An example is:

fmt == "9.1.0"     [ fmt ]                    git *    https://github.com/fmtlib/fmt.git
Catch2 == "v3.3.1" [ Catch2::Catch2WithMain ] git test https://github.com/catchorg/Catch2.git
m
!std c++17
!build cmake
# this is a comment

This is quite simple and powerful, with few lines describing the following:

• take fmt project from git repository in specific version
• take Catch2 project from git repository in specific version and use it for tests only
• take system -lm dependency
• C++ standard c++17 is used
• build system cmake is used

The git part could be any package manager, such as conan and vcpkg, although not implemented yet! The git can be specified for cmake or bazel, like cmake+git or bazel+git.

It can also be bcr, for the Bazel Central Registry, or more specifically: bazel+bcr (not supported for cmake+bcr)

Ongoing extensions for cxxdeps

Some ongoing extensions will allow managing dev dependencies, such as build systems (cmake, bazel, etc) and C/C++ package managers (conan, etc), all automatically on cxxdeps.txt (or exclusively on cxxdeps.dev.txt):

cmake == *          [ cmake ]       pip dev [ ninja ]
ninja:windows == *  [ ninja ]       choco dev
ninja:linux == *    [ ninja-build ] apt dev
bazel:windows == *  [ bazelisk ]    choco dev 
bazel:linux == *    [ bazelisk ]    npm dev 
conan == *          [ conan ]       pip dev

Note that we can support triplet package notation on project name, so as different system package managers (such as apt on ubuntu/debian). Some package dependency notation can be useful as well to orchestrate installation flow, when necessary (as an example, ninja could be forcefully installed before cmake).

Other extension is some build section... similar to dev, but it installs automatically before build process. The build can be seen as a mandatory dev dependency. Some configure actions and patches could also happen in build phase (which are in fact some pre-build actions).

cxxdeps is a cool thing!

• In fact, this was the most motivating part of this project, so feel free to check more painful experiences directly on manydeps-gmp project!

Writing cxxdeps in .toml format

It is currently possible to write cxxdeps.toml file, that automatically generates cxxdeps.txt and cxxdeps.dev.txt files. Some users may find this easier to understand:

[all]
fmt={ git="https://github.com/fmtlib/fmt.git", tag="9.1.0", links=["fmt"] }
m={ links=["m"] }
pthread={}

[test]
catch2={ git="https://github.com/catchorg/Catch2.git", tag="v3.3.1", links=[
    "Catch2::Catch2WithMain"
] }

[dev]
bazel=[{ choco=["bazelisk"], platform="windows" }, { npm=["bazelisk"], platform="linux" }]
ninja=[{ choco=["ninja"], platform="windows" }, { apt=["ninja-build"], platform="linux" }]
cmake={ pip=["cmake"], deps=["ninja"] }
conan={ pip=["conan"] }

Here one can find sections all (equivalent to *), test and dev. This example install system libraries -lm and -lpthread for runtime dependencies (all), catch2 test library linked with cmake Catch2::Catch2WithMain, and defines several dev packages.

Check an example in project3 with: python3 cxxbuild/cxxbuild.py demo/project3

Drawbacks

None that I know, yet :)

Some people may dislike the imposed organization, like src/ and tests/, but it can be changed manually on script. The idea here is to really make a simplistic script, that really works with highly complex setups (such as taking dependencies from remote and dealing with build systems like cmake and bazel). These things are hard to do even for some experienced c++ programmers... so, as long as it is simple and it works, that is fine! If it doesn't work, file an issue!

Build !options on cxxdeps

The cxxdeps.txt file allows defining some usual command line parameters with ! prefix. Examples:

• Parameter --c++20 appears on file as !std c++20
• Parameter --cmake appears on file as !build cmake
• Parameter --bazel appears on file as !build bazel
• Parameter --include dir appears on file as !include "dir"

Command-line parameters have priority over cxxdeps.txt and can overwrite or complement them (with exception of !build parameter that cannot be overwritten).

In the future, the !options could be limited by operating system, e.g., !option:windows.

Related Works

• See ccbuild from debian
  • See bneijt/ccbuild
• See Mantle project (experimental but with similar ideas)

None of them support dependencies, such as cxxdeps.txt, or even build systems such as cmake and bazel.

Hopefully, when this project is fully finished, C++ will be a better place for all of us :)

Case of Study

In order to check the capabilities of cxxbuild, it was used to build the C/C++ ccbuild tool. Unfortunately, few tweaks were necessary in the generated CMakeLists, due to FLEX dependency, but it was quite easy on general. See Issue 34 on ccbuild project

General instructions:

• Create cxxdeps.txt file:

bobcat
gnutls
fl
png
# apt install flex 
# apt install libboost-all-dev
# apt install gnutls-dev
# apt install libbobcat-dev
# libpng-dev

• Use the following build script: cxxbuild . --tests test --include src --include src/sourceScanner --c++20
• Add this to last line of CMakeLists: add_definitions(-DVERSION="v2.0.7-39-gdf7b35c")
• Add this to SOURCES: ${FLEX_SourceScanner_OUTPUTS}
• Add these two lines before the SOURCES:

find_package(FLEX)
FLEX_TARGET(SourceScanner "src/sourceScanner/lexer"  "src/sourceScanner/yylex.cc" )

And that's it! It builds all avaliable targets and tests for ccbuild.

Acknowledgements

Thanks for those trying to use and improve this software. Specially, thanks Fellipe Pessanha for early suggesting integrating toml support for cxxdeps.

Citation

Igor Machado Coelho. (2023). cxxbuild project. Zenodo. https://doi.org/10.5281/zenodo.10447208

License

Dual licensed: Creative Commons Attribution 4.0 International OR MIT License

Copyleft 2023

Igor Machado Coelho