[songgaoye]

What problem does this PR solve?

Issue Number: resolve

Problem Summary:

UB shared-memory names are generated with snprintf, but the previous code
only handled negative return values. An overlong endpoint name could therefore
silently truncate the generated shared-memory name, causing collisions or use
of an unintended shared-memory object.

What is changed and the side effects?

Changed:

• Treat snprintf truncation as an error when generating client and server
  shared-memory names.
• Reject UBS setup rather than use a truncated name.
• Release the acquired transaction slot when client local-name construction
  fails.
• Add regression coverage that limits the transaction manager to one slot and
  verifies the slot can be acquired again after the rejected setup.

Side effects:

• Performance effects:

  None on successful setup paths.

• Breaking backward compatibility:

  Connections whose generated shared-memory names exceed the fixed limit now
  fall back instead of silently using a truncated name.

---

Check List:

• Please make sure your changes are compilable.
• When providing us with a new feature, it is best to add related tests.
• Please follow Contributor Covenant Code of Conduct.

[Copilot]

🟡 Changes recommended

The regression test does not cover the independently changed server-handshake path for overlong peer names, leaving its collision-prone fallback behavior unverified.

1 open issue

• Test overlong peer-name fallback in server handshake · New

What changed in this PR

This PR hardens UB shared-memory setup by rejecting names that would be truncated by snprintf, preventing collisions or unintended shared-memory object usage, and releases the client transaction slot when local-name construction fails.

Changes:

• Detect truncation when constructing client, server, and remote shared-memory names.
• Fall back from UB when generated names cannot be represented safely.
• Add regression coverage for transaction-slot reuse after rejected setup.

File	Description
test/​brpc_ubring_unittest.cpp	Adds regression coverage verifying that a rejected overlong local shared-memory name releases the transaction slot for reuse.
src/​brpc/​ubshm/​ub_ring.cpp	Rejects truncated client and remote shared-memory names and releases the client transaction when local-name construction fails.
src/​brpc/​ubshm/​ub_endpoint.cpp	Rejects truncated server shared-memory names during handshake and falls back from UB.

_{Review effort: Lite}

[Copilot]

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Copilot review overview

3 open issues

• This LOG(ERROR) << ... , local_name, result; uses the comma operator, so local_name and… · New
• After releasing _trx back to the manager, _trx remains as a non-null member pointer even though… · New
• In a function parameter, char shm_name[SHM_MAX_NAME_BUFF_LEN] decays to char* and does not… · New

1 resolved since last review

• Test overlong peer-name fallback in server handshake

_{Review effort: Lite}

[Copilot]

🟢 Approval recommended

The review found no active issues, with regression coverage added for truncation rejection and transaction-slot recovery.

No open issues 🎉

3 resolved since last review

• After releasing _trx back to the manager, _trx remains as a non-null member pointer even though…
• This LOG(ERROR) << ... , local_name, result; uses the comma operator, so local_name and…
• In a function parameter, char shm_name[SHM_MAX_NAME_BUFF_LEN] decays to char* and does not…

_{Review effort: Lite}