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Cross-compilation

Overview

Open Robotics provides pre-built ROS 2 packages for multiple platforms, but a number of developers still rely on cross-compilation for different reasons such as:

• The development machine does not match the target system.

• Tuning the build for specific core architecture (e.g. setting -mcpu=cortex-a53 -mfpu=neon-fp-armv8 when building for Raspberry Pi3).

• Targeting a file system other than the ones supported by the pre-built images released by Open Robotics.

How does it work ?

Cross-compiling simple software (e.g. no dependencies on external libraries) is relatively simple and only requiring a cross-compiler toolchain to be used instead of the native toolchain.

There are a number of factors which make this process more complex:

• The software being built must support the target architecture. Architecture specific code must be properly isolated and enabled during the build according to the target architecture. Examples include assembly code.

• All dependencies (e.g. libraries) must be present, either as pre-built or cross-compiled packages, before the target software using them is cross-compiled.

• When building software stacks (as opposed to standalone software) using build tools (e.g. colcon), it is expected that the build tool provides a mechanism to allow the developer to enable cross-compilation on the underlying build system used by each piece of software in the stack.

Alternatives

An alternative to cross-compilation is to build multi-platform Docker images using docker buildx.