Selecting build types

CMake provides default compiler optimization flags for every default build configuration.

Helpful Resources

• Default and Custom Configurations
• CMAKE_CONFIGURATION_TYPES
• CMAKE_BUILD_TYPE

Description

The CMake variable CMAKE_CONFIGURATION_TYPES provides a list with four default build configurations. The initial options for the IAR C/C++ Compiler in each default configuration are:

Build configuration	Default compiler options	Remarks
Debug	-r
Release	-Oh -DNDEBUG
RelWithDebInfo	-Oh -DNDEBUG -r
MinSizeRel	-Ohz -DNDEBUG	Disabled by default in "Ninja Multi-Config". See #22266.

This list can be expanded with user-defined custom build configurations.

Examples

The examples below illustrate some relevant differences between configuring a project for the Ninja Multi-Config and for the Ninja generators. Note that the generator names are case-sensitive and must be defined at configure-time.

Ninja Multi-Config generator

The Ninja Multi-Config generator can be selected at configure-time with -G"Ninja Multi-Config":

cmake -Bbuild -G"Ninja Multi-Config" [--toolchain /path/to/your-iar-toolchain-file.cmake]

This command will configure the build system to reside inside the build directory. For each build configuration, there will be a build/<configuration> sub-directory containing all the outputs (objects, libraries and executable files). That way, the build directory can hold all build configuration results at the same time when building the project:

cmake --build build --config debug
cmake --build build --config release
cmake --build build --config relwithdebinfo
cmake --build build --config minsizerel

Note

• At build-time, the configuration name in the --config <configuration> parameter is case-insensitive.
• Build with --verbose for inspecting the command-line details.

Ninja generator

The Ninja generator can be selected at configure-time with -GNinja. For this generator, the build type for the build system needs to be selected with the CMAKE_BUILD_TYPE variable. Note that specifying the build-type here is case-sensitive. Example:

cmake -Bbuild -GNinja -DCMAKE_BUILD_TYPE=Debug [--toolchain /path/to/your-iar-toolchain-file.cmake]

This command will configure the build system for the "Debug" configuration to reside inside the build directory which will contain all the outputs (objects, libraries and executable files). When building the project:

cmake --build build --verbose

For switching from one build configuration to another there are essentially two options: a) erase build and reconfigure the build system with a different CMAKE_BUILD_TYPE, or, b) use a different -B<build-directory>.

Note

• Build with --verbose for inspecting the command-line details.

Summary

Which generator should one to use? While we tend to recommend "Ninja Multi-Config" for its simplicity when switching from one build configuration to another. Ultimately both generators are capable and immediately selectable at configure-time, without even touching the CMakeLists.txt project file.

Related Articles

• Creating custom build configurations