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fix(post): state the one definition rule of the hookless clone mixin - #266
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Episode 4 now says every translation unit must see the same classes in the searched namespace, from a review of the old repo's port, and that the port checks it with a two-unit test. Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
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🟡 Changes recommended
The post needs to clarify that another namespace can contain a separate closed hierarchy but cannot extend the original base’s clone dispatch, which still throws for the out-of-namespace derived class.
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What changed in this PR
This documentation-only update clarifies the one definition rule requirement for Episode 4's reflection-based, hookless clone mixin.
Changes:
- Adds a cross-reference from the namespace-search explanation to the new section.
- Explains the need for consistent class sets across translation units, possible failure symptoms, and the port's two-unit verification test.
| File | Description |
|---|---|
src/content/posts/2026-12-21-std-polymorphic-instead-of-clone.mdx |
Documents cross-translation-unit consistency requirements for the hookless mixin. |
Review effort: Balanced
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| ## One definition rule for the hookless mixin | ||
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| Every translation unit of a program must see the same classes in the searched namespace, so the hierarchy belongs in one header. A unit that sees a different set generates a different `clone()` for the same specialization, which is undefined. It can show up as `clone_unavailable` for a class the caller can see. The way to extend the set is another namespace. The 2014 repo's port checks the requirement with a test that links two translation units and compares the class lists each one sees. |
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Episode 4 gains a short section: every translation unit must see the same classes in the searched namespace, or the hookless clone() differs between units for the same specialization. From a review of the old repo's port, which now guards it with a two-unit test and a mutant twin. Prose-lint clean, production build exits 0.
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