Ninja and Make

Learn Ninja and Make generators.

What are Ninja and Make?

CMake chooses a generator: the two most common are Make and Ninja. Make is universal and found on every Unix; Ninja offers faster incremental builds especially for large projects.

You pick the generator with the -G flag: cmake -G "Ninja" . or cmake -G "Unix Makefiles" .. To build the generated files you run make for Make or ninja for Ninja. Ninja does parallel builds by default; Make needs explicit parallelism like make -j4.

CMAKE_BUILD_TYPE

The CMAKE_BUILD_TYPE variable sets the build type: Debug (debug symbols, no optimization), Release (full optimization), RelWithDebInfo (optimization + symbols). It is set from the command line as cmake -DCMAKE_BUILD_TYPE=Release ..

Example: cmake -G "Ninja" -DCMAKE_BUILD_TYPE=Release . produces Ninja files for a release build. Running ninja then compiles the program optimized. Inside CMakeLists.txt you can write if(CMAKE_BUILD_TYPE STREQUAL "Debug") to add type-specific commands. This lets one build file serve both development and production builds.

Exercise Write a release build configuration

Write a CMakeLists.txt. Add cmake_minimum_required(VERSION 3.20) and project(MyApp). Define add_executable(myapp main.cpp). Add a comment # cmake -G "Ninja" -DCMAKE_BUILD_TYPE=Release . at the end.

Show example solution

cmake_minimum_required(VERSION 3.20)
project(MyApp)
add_executable(myapp main.cpp)
# cmake -G "Ninja" -DCMAKE_BUILD_TYPE=Release .

Test yourself

Complete the generator name
```
cmake -G "____" .
```
Show answer
```
cmake -G "Ninja" .
```
Match each piece to its role

cmake -G "Ninja"

Generates Ninja
cmake -G "Unix Makefiles"

Generates Makefiles
ninja

Builds with Ninja
make -j4

Parallel Make build
Why prefer Ninja?
- It produces smaller files
- It needs less code
- It does faster incremental builds
- It is the default everywhere
Show answer

It does faster incremental builds — Ninja speeds up incremental builds, especially for large projects.

Next lesson: Summary - Build systems

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