Backward Compatibility

This page is a work in progress

Type of Backward Compatibility

Libraries can typically define backward compatibility with respect to the API and ABI. GNU Radio is a library, but also has a number of other dimensions.

C++ Libraries

• C++ ABI compatibility means that existing binaries that link against GR will dynamically link and run with a new version of GR.
• C++ API compatibility means that a developer's source code (e.g, an OOT module) will build against a new version of GR with no modification.

Python Modules/Libraries

• Pure Python
• C/C++ wrappers (SWIG/PyBind11)
• Embedded Python blocks

GNU Radio Companion

• Schema for block YAML
• Schema for GRC YAML
• Block description (parameters, ...)
• Template code for Python and C++
• Autogenerated code

Data Interfaces

• Serialization (PMT)
• ZMQ (e.g., timeouts)
• Networking (e.g., MTU)

Streams

• Type definitions (stable)
• Types available for a block
• Block ports, whether required, whether number is configurable or fixed

Messages

• Message ports, whether required
• Format
• Meaning

Tags

• When required, when produced
• Format
• Meaning

Text

• Console output
• Logging

Dependencies

• Build environment
• Runtime environment (usually solved by packaging)

Configuration

• Files for GR, GRC
• Environment variables

Behavior

• Algorithm changes
• Runtime changes (e.g., threading behavior)
• Generated GUI (layout, operation)

GNU Radio Versioning

GR uses semantic versioning with four digits (W.X.Y.Z).

• W: general concept, fixed at "3" until a major shift occurs
• X: API version for C++ libraries and Python modules. External C++ and Python code may require modification, sometimes significant.
• Y: ABI version for C++ libraries. External C++ code needs to be rebuilt, but not modified.
• Z: Patch version. No rebuild required.