IGNITION_MATH_MAJOR_VERSION is undefined for ign-math4

[traversaro]

Environment

• OS Version: Ubuntu 20.04
• Source or binary build? Binary, in particular:

straversaro@IITICUBLAP102:~$ apt list --installed | grep math4

WARNING: apt does not have a stable CLI interface. Use with caution in scripts.

libignition-math4-dev/focal,now 4.0.0+dfsg1-5ubuntu1 amd64 [installed]
libignition-math4/focal,now 4.0.0+dfsg1-5ubuntu1 amd64 [installed,automatic]

Description

• Expected behavior: IGNITION_MATH_MAJOR_VERSION is a macro expected to have the integer value of the major version of ignition math.
• Actual behavior: For IgnMath4, that macro is empty

Steps to reproduce

Just run cat /usr/include/ignition/math4/ignition/math/config.hh and inspect the output.

Output

straversaro@IITICUBLAP102:~$ cat /usr/include/ignition/math4/ignition/math/config.hh
/* Config.hh. Generated by CMake for ignition-math. */

/* Version number */
#define IGNITION_MATH_MAJOR_VERSION
#define IGNITION_MATH_MINOR_VERSION
#define IGNITION_MATH_PATCH_VERSION

#define IGNITION_MATH_VERSION "4.0"
#define IGNITION_MATH_VERSION_FULL "4.0.0"

#define IGNITION_MATH_VERSION_NAMESPACE v4

#define IGNITION_MATH_VERSION_HEADER "Ignition math, version 4.0.0\nCopyright (C) 2014 Open Source Robotics Foundation.\nReleased under the Apache 2.0 License.\n\n"

/* #undef IGNITION_MATH_BUILD_TYPE_PROFILE */
/* #undef IGNITION_MATH_BUILD_TYPE_DEBUG */
/* #undef IGNITION_MATH_BUILD_TYPE_RELEASE */

[traversaro]

A bit of background: the issue was fixed for ign-math >= 6 in #151 . However, another major change of ign-math6 w.r.t. to ign-math4 was the semantics of Pose3::operator*, see https://osrf-migration.github.io/ignition-gh-pages/#!/ignitionrobotics/ign-math/pull-requests/301/page/1 and #60 for some background. For this reason, if you need to have a plugin that uses Pose3::operator* and you want that it works fine both with Gazebo 9 (EOL: Jan 2023) and Gazebo 11 (EOL: Jan 2025), you need to have some logic like:

#ifdef IGNITION_MATH_IS_GREATER_THEN_5 
        ignition::math::Pose3d world_H_cylinder = world_H_link*link_H_cylinder;
#else 
        ignition::math::Pose3d world_H_cylinder = link_H_cylinder*world_H_link;
#endif

In my case, I was using IGNITION_MATH_MAJOR_VERSION >= 5, so:

#if IGNITION_MATH_MAJOR_VERSION >= 5
        ignition::math::Pose3d world_H_cylinder = world_H_link*link_H_cylinder;
#else 
        ignition::math::Pose3d world_H_cylinder = link_H_cylinder*world_H_link;
#endif

but it turns out that this results in a compilation error:

/home/gnava/Software/github/dic-iit/component_ironcub/software/gazebo/plugins/jets-plugin/jets-plugin.cc:595:41: error: operator '>=' has no left operand
  595 |         #if IGNITION_MATH_MAJOR_VERSION >= 5
      |                                         ^~

due to the issue described in this issue.

If anyone is affected by the same problem, as long as you are compiling a Gazebo plugin you can rely on the fact that Gazebo 9 uses ign-math4 and Gazebo 11 uses ign-math6, and so you can just use the GAZEBO_MAJOR_VERSION as a proxy for the ign-math version, i.e. this will work fine:

#if GAZEBO_MAJOR_VERSION >= 11
        ignition::math::Pose3d world_H_cylinder = world_H_link*link_H_cylinder;
#else 
        ignition::math::Pose3d world_H_cylinder = link_H_cylinder*world_H_link;
#endif

Documenting this is the main reason for which I opened this issue, as I do not plan fix the issue itself.

[azeey]

Closing since ign-math4 is EOL.