how_to_set_environment_variables.md

How to set environment variables

Introduction

Agnocast uses the LD_PRELOAD to replace the following memory allocation/deallocation functions:

• malloc
• free
• calloc
• realloc
• posix_memalign
• aligned_alloc
• memalign

The hook library is generated as libagnocast_heaphook.so, so Agnocast requires to set LD_PRELOAD to libagnocast_heaphook.so.

Integrate with ROS 2 launch

You can set environment variables through ROS 2 launch file systems as follows. To run the other application using LD_PRELOAD with Agnocast, you must add "libagnocast_heaphook.so" to the existing 'LD_PRELOAD' contents without modifying the libraries already specified there.

<node pkg="..." exec="..." name="...">
  <env name="LD_PRELOAD" value="libagnocast_heaphook.so:$(env LD_PRELOAD '')" />
</node>

<!-- Recommended: use agnocast_components package -->
<node_container pkg="agnocast_components" exec="agnocast_component_container" name="...">
  <env name="LD_PRELOAD" value="libagnocast_heaphook.so:$(env LD_PRELOAD '')" />
</node_container>

<!-- Deprecated: agnocastlib package (will be removed in future versions) -->
<node_container pkg="agnocastlib" exec="agnocast_component_container" name="...">
  <env name="LD_PRELOAD" value="libagnocast_heaphook.so:$(env LD_PRELOAD '')" />
</node_container>

import os

container = ComposableNodeContainer(
    ...,
    additional_env={
        'LD_PRELOAD': f"libagnocast_heaphook.so:{os.getenv('LD_PRELOAD', '')}",
    },
)

Warning

If the other applications hooks memory allocation/deallocation functions that are hooked by Agnocast, it cannot be used together with Agnocast.