Building C++ Libraries Sample
You can open this sample in an IDE that supports Gradle. |
This guide demonstrates how to create a C++ library with Gradle using gradle init
.
You can follow the guide step-by-step to create a new project from scratch or download the complete sample project using the links above.
The C++ Library Plugin is not compatible with the configuration cache. |
What you’ll build
You’ll generate a C++ library that follows Gradle’s conventions.
What you’ll need
-
A text editor or IDE - for example IntelliJ IDEA
-
A Java Development Kit (JDK), version 8 or higher - for example AdoptOpenJDK
-
The latest Gradle distribution
-
An installed C++ compiler. See which C++ tool chains are supported by Gradle.
Create a project folder
Gradle comes with a built-in task, called init
, that initializes a new Gradle project in an empty folder.
The init
task uses the (also built-in) wrapper
task to create a Gradle wrapper script, gradlew
.
The first step is to create a folder for the new project and change directory into it.
$ mkdir demo $ cd demo
Run the init task
From inside the new project directory, run the init
task using the following command in a terminal: gradle init
.
When prompted, select the 2: library
project type and 5: C++
as the implementation language.
Next you can choose the DSL for writing buildscripts - 1 : Kotlin
or 2: Groovy
.
For the other questions, press enter to use the default values.
The output will look like this:
$ gradle init Select type of build to generate: 1: Application 2: Library 3: Gradle plugin 4: Basic (build structure only) Enter selection (default: Application) [1..4] 2 Select implementation language: 1: Java 2: Kotlin 3: Groovy 4: Scala 5: C++ 6: Swift Enter selection (default: Java) [1..6] 5 Project name (default: demo): Select build script DSL: 1: Kotlin 2: Groovy Enter selection (default: Kotlin) [1..2] Generate build using new APIs and behavior (some features may change in the next minor release)? (default: no) [yes, no] BUILD SUCCESSFUL 1 actionable task: 1 executed
The init
task generates the new project with the following structure:
├── gradle (1)
│ ├── libs.versions.toml (2)
│ └── wrapper
│ ├── gradle-wrapper.jar
│ └── gradle-wrapper.properties
├── gradlew (3)
├── gradlew.bat (3)
├── settings.gradle.kts (4)
└── lib
├── build.gradle.kts (5)
└── src
├── main
│ └── cpp (6)
│ │ └── hello.cpp
│ └── headers
│ └── app.h
└── test
└── cpp (7)
└── hello_test.cpp
├── gradle (1)
│ ├── libs.versions.toml (2)
│ └── wrapper
│ ├── gradle-wrapper.jar
│ └── gradle-wrapper.properties
├── gradlew (3)
├── gradlew.bat (3)
├── settings.gradle (4)
└── lib
├── build.gradle (5)
└── src
├── main
│ └── cpp (6)
│ │ └── hello.cpp
│ └── headers
│ └── app.h
└── test
└── cpp (7)
└── hello_test.cpp
1 | Generated folder for wrapper files |
2 | Generated version catalog |
3 | Gradle wrapper start scripts |
4 | Settings file to define build name and subprojects |
5 | Build script of lib project |
6 | Default C++ source folder |
7 | Default C++ test source folder |
You now have the project setup to build a C++ library.
Review the project files
The settings.gradle(.kts)
file has two interesting lines:
rootProject.name = "demo"
include("lib")
rootProject.name = 'demo'
include('lib')
-
rootProject.name
assigns a name to the build, which overrides the default behavior of naming the build after the directory it’s in. It’s recommended to set a fixed name as the folder might change if the project is shared - e.g. as root of a Git repository. -
include("lib")
defines that the build consists of one subproject calledlib
that contains the actual code and build logic. More subprojects can be added by additionalinclude(…)
statements.
Our build contains one subproject called lib
that represents the C++ library we are building.
It is configured in the lib/build.gradle(.kts)
file:
plugins {
`cpp-library` (1)
`cpp-unit-test` (2)
}
library {
targetMachines.add(machines.linux.x86_64) (3)
}
plugins {
id 'cpp-library' (1)
id 'cpp-unit-test' (2)
}
library {
targetMachines.add(machines.linux.x86_64) (3)
}
1 | Apply the cpp-library plugin to add support for building C++ libraries |
2 | Apply the cpp-unit-test plugin to add support for building and running C++ test executables |
3 | Set the target operating system and architecture for this library |
The file src/main/cpp/hello.cpp
is shown here:
/*
* This source file was generated by the Gradle 'init' task
*/
#include <iostream>
#include <stdlib.h>
#include "demo.h"
std::string demo::Greeter::greeting() {
return std::string("Hello, World!");
}
The generated test, src/test/cpp/hello.cpp
is shown next:
/*
* This source file was generated by the Gradle 'init' task
*/
#include "demo.h"
#include <cassert>
int main() {
demo::Greeter greeter;
assert(greeter.greeting().compare("Hello, World!") == 0);
return 0;
}
The generated test class has a single C++ executable test.
The test instantiates the Hello
class, invokes a method on it, and checks that it returns the expected value.
Build the library
$ ./gradlew build BUILD SUCCESSFUL in 0s 4 actionable tasks: 4 executed
The first time you run the wrapper script, gradlew , there may be a delay while that version of gradle is downloaded and stored locally in your ~/.gradle/wrapper/dists folder.
|
The build
task compiles the C++ sources, links the object files into a shared library, and runs the tests.
To build a static library, please refer to the static library sample.
Dependencies on other projects isn’t covered in this guide. To learn more about this subject, have a look at the transitive dependency sample for a demonstration. |
Publishing libraries to Maven repositories is outside the scope of this guide. To learn more about this subject, have a look at the simple library sample for a demonstration. |
Gradle integrates with several IDEs: Visual Studio, Xcode and Clion. To learn more, have a look at their respective linked documentation to configure those IDE integration in your project. |
Publish a Build Scan
The best way to learn more about what your build is doing behind the scenes, is to publish a build scan.
To do so, just run Gradle with the --scan
flag.
$ ./gradlew build --scan BUILD SUCCESSFUL in 0s 4 actionable tasks: 4 executed Publishing a build scan to scans.gradle.com requires accepting the Gradle Terms of Service defined at https://gradle.com/terms-of-service. Do you accept these terms? [yes, no] yes Gradle Terms of Service accepted. Publishing build scan... https://gradle.com/s/5u4w3gxeurtd2
Click the link and explore which tasks where executed, which dependencies where downloaded and many more details!
Summary
That’s it! You’ve now successfully configured and built a C++ library project with Gradle. You’ve learned how to:
-
Initialize a project that produces a C++ library
-
Build the library, which includes running its tests
Next Steps
-
Make your way to the native samples repository to see the C++ plugins in action for common scenarios such as transitive dependencies, custom source layout, and static library.
-
Check out the user manual chapter on Building C++ projects