Fix parameter passing in generate_state_database.cpp

[XueZhiai123]

Background
MoveIt 2 provides the “Planning with Approximated Constraint Manifolds” feature to accelerate constrained motion planning. The generate_state_database.cpp file is responsible for building the constraint state database, but due to the parameter-retrieval function’s signature using an rvalue reference, both options.samples and options.edges_per_sample remain at their default value of 0. As a result, the sampling and connection loops never execute.
Problem
In the original implementation, the parameter-retrieval function is declared as:
static bool get_uint_parameter_or(
const rclcpp::Node::SharedPtr& node,
const std::string& param_name,
size_t&& result_value,
const size_t default_value)
{ … }
Passing result_value as a size_t&& rvalue reference prevents the retrieved parameter value from being written back to the caller’s variable.
Consequently, both options.samples and options.edges_per_sample stay at 0, causing the state database generation to fail with:
[INFO] […] Generated 0 states in 0.000005 seconds
[ERROR] […] No StateStoragePtr found – implement better solution here.
Solution
Change the function signature to use an lvalue reference of type unsigned int&, ensuring that the retrieved parameter is correctly assigned:
-static bool get_uint_parameter_or(

• const rclcpp::Node::SharedPtr& node,
• const std::string& param_name,
• size_t&& result_value,
• const size_t default_value)
  +static bool get_uint_parameter_or(

• const rclcpp::Node::SharedPtr& node,
• const std::string& param_name,
• unsigned int& result_value,
• const size_t default_value)
  {
  int param_value;
  if (node->get_parameter(param_name, param_value))
  {
  if (param_value >= 0)
  {

•       result_value = static_cast<size_t>(param_value);
  

•       result_value = static_cast<unsigned int>(param_value);
        return true;
    }
    RCLCPP_WARN_STREAM(...);
  

  }
  result_value = default_value;
  return true;
  }
  Key Changes
  Changed parameter type from size_t&& to unsigned int&.
  Cast the retrieved int to unsigned int instead of size_t.
  Preserved the original default-value fallback and warning logic.
  Verification
  After rebuilding and running the generation script locally, you can now observe proper sampling and connection progress:
  [INFO] […] 90% complete
  [INFO] […] Computed possible connexions in 14.77 seconds. Added 2373 connexions
  [INFO] […] Spent 202.56 seconds constructing the database
  The Constraint Approximation Database is successfully created and saved to the specified path.
  Related Work
  There is an existing community PR (see Fixes for using generate-state_database #1412) addressing issues with generate_state_database, but that effort focuses on different aspects. This fix targets only the parameter-retrieval signature, so the two can be merged independently.

[rhaschke]

Actually, I don't understand why this function was introduced at all.
Node::get_parameter_or() is a templated function that should work for uint as well.
Could you please try to use that function directly?

[XueZhiai123]

Actually, I don't understand why this function was introduced at all. Node::get_parameter_or() is a templated function that should work for uint as well. Could you please try to use that function directly?

In this snippet, the author implemented a custom getUintParameterOr utility function instead of calling node->get_parameter_or directly. This approach offers two main advantages:

size_t support
The native rclcpp::Node::get_parameter_or template supports built-in types (e.g., int, double, bool) and standard containers, but it does not directly handle alias types like size_t (often unsigned long).

Seamless conversion
getUintParameterOr reads the parameter into an intermediate int param_value and then casts it via static_cast<size_t>(param_value). This lets callers assign the result directly to construction_opts.samples (of type size_t) without having to perform a manual cast.

Since both samples and edges_per_sample were originally defined as unsigned int, this helper function ensures the values are read and stored correctly in their intended unsigned integer types.

[rhaschke]

The native rclcpp::Node::get_parameter_or template supports built-in types (e.g., int, double, bool).

I see. Unsupported parameter types yield an "undefined symbol" error, I guess?

[rhaschke]

You should consistently use size_t or unsigned int:

Suggested change

	unsigned int& result_value, const size_t default_value)
	unsigned int& result_value, const unsigned int default_value)

[XueZhiai123]

Thanks for the suggestion! You’re right—I’ll unify all related types in the function signature to unsigned int, including the default value type. I’ll verify everything locally tomorrow and then immediately update the branch and push a new PR. Thank you again for your guidance, and I look forward to any further feedback!

[XueZhiai123]

Thanks for the suggestion! I’ve unified the types to unsigned int (including the default value) and pushed the update. Please take another look.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 46.22%. Comparing base (7d6e2ab) to head (6de5a4d).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3545   +/-   ##
=======================================
  Coverage   46.22%   46.22%           
=======================================
  Files         720      720           
  Lines       62713    62713           
  Branches     7594     7594           
=======================================
  Hits        28985    28985           
+ Misses      33562    33561    -1     
- Partials      166      167    +1     

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