[jll63]

(Written by Claude Code, on behalf of @jll63.)

Found while auditing the library for memory-safety defects. Two commits: a fix, and the documentation the audit suggested.

Fix

The copy-assignment of a smart virtual_ptr from a smart pointer, virtual_ptr<SmartPtr>::operator=(const Other&), dereferenced the source unconditionally:

obj = other;
vp = detail::box_vptr<use_indirect_vptrs>(detail::acquire_vptr<Registry>(*other));

The constructor from the same argument and the move-assignment both guard with other ? acquire_vptr(*other) : null_vptr; this overload was the one exception. Assigning an empty std::shared_ptr lvalue therefore read the dynamic type of a null object (UBSan: "reference binding to null pointer", then a SEGV in std_rtti::dynamic_type). The rvalue path, p = dog_ptr(), was fine and was the only one the tests covered.

This aligns the overload with its siblings, and adds the lvalue case to test_smart_virtual_ptr_value_semantics.cpp, where it runs for both std::shared_ptr and boost::intrusive_ptr.

Verified with -fsanitize=address,undefined and runtime checks on: the new test fails on the unfixed header and passes with the fix; the full suite of 79 tests and 33 examples is clean under the same flags.

Documentation

Nothing else in the audit was a bug; these are the properties a security-minded user has to know and the pages did not say:

• error_handling.adoc, new Runtime Checks section: without the policy, a call on an unregistered class reads a v-table slot that initialize never filled and calls the word it finds there; what the policy costs; when to keep it in release builds.
• shared_libraries.adoc: between a library's unload and the next initialize, its overriders are stale function pointers in the tables, and runtime_checks does not notice by itself (finalize first makes it refuse). The library performs no synchronization: initialize, finalize and loading or unloading must not overlap with dispatch in other threads, and concurrent loads race on the registration lists.
• registries_and_policies.adoc: the dispatch tables and static v-table pointers live in writable memory, unlike the compiler's v-tables, and may be made read-only after initialize returns.
• Reference: initialize gains a Thread safety paragraph; the virtual_ptr pointer constructor and assignment state that the pointer must not be null (the smart-pointer overloads accept an empty pointer, this one reads the object); trace::from_env notes that the trace prints addresses, so a privileged program should not let the environment enable it.

🤖 Generated with Claude Code

https://claude.ai/code/session_016fFU6fW4SeTaPcAAEt41xu

[cppalliance-bot]

An automated preview of the documentation is available at https://143.openmethod.prtest3.cppalliance.org/libs/openmethod/doc/html/index.html

If more commits are pushed to the pull request, the docs will rebuild at the same URL.

2026-11-07 01:57:02 UTC