Support 64-bit integers in daemon XML-RPC

[sylvesterkaczmarek]

Summary

Fixes #629.

Python's standard XML-RPC marshaller rejects integers outside the signed 32-bit range even though its unmarshaller supports the standard i8 extension.

Register a custom integer marshaller that:

• preserves the normal int tag for signed 32-bit values
• uses i8 for signed 64-bit values
• continues rejecting values outside signed 64-bit range

This allows daemon RPC payloads to carry 64-bit integer values without changing existing 32-bit output.

Testing

Added focused round-trip coverage for:

• signed 32-bit values using int
• positive and negative values outside 32-bit using i8
• signed 64-bit boundaries
• rejection outside the signed 64-bit range

Did you use Generative AI?

Yes. AI was used to assist with tests.

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[fujitatomoya]

the implementation to patch the mashaller looks good to work, but i would take the other path to address the root cause such as JSON-RPC 2.0 over the existing loopback HTTP transport. at least, this needs to be tested.

[sylvesterkaczmarek]

The requested transport-level coverage is now present on the current head: the test uses ros2daemon's own XML-RPC server/client path and exercises a 64-bit value through the actual transport. The review thread is resolved, the PR is clean/mergeable, and DCO plus Summary are green. Could you re-review the current head when convenient?

[sylvesterkaczmarek]

The requested transport-level coverage remains present on the current clean head: the test uses ros2daemon's actual XML-RPC server/client path and exercises a 64-bit integer across the HTTP/XML-RPC transport. The PR intentionally remains scoped to compatibility with the existing transport rather than a JSON-RPC redesign. DCO/Summary are green, there are zero unresolved review threads, and no current failing checks. Re-requesting review.

[sylvesterkaczmarek]

@fujitatomoya This branch has now been refreshed onto current main (head 731ef82). The transport-level 64-bit XML-RPC coverage remains present. All review threads are resolved, and there are no current failing or pending checks. Could you re-review the current head when convenient?