isocpp / isocpp/CppCoreGuidelines
Parameter pass-by-value heuristic: trivial copyability issue, and incomplete type issue
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Description
F.16 says:
(Simple) ((Foundation)) Warn when a parameter being passed by value has a size greater than 2 * sizeof(void*). Suggest using a reference to const instead.
(Simple) ((Foundation)) Warn when a parameter passed by reference to const has a size less or equal than 2 * sizeof(void*). Suggest passing by value instead.
Two problems that have come up with this advice:
- (easy) It should also say "and is trivially copyable"
- (harder) When the parameter is of an incomplete user-defined type (class, enum, union) then we can't tell its size and trivial copyability
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start with guideline F.16 and review the two parameter pass-by-value recommendations quoted in the issue. Clarify how the advice should account for trivial copyability and incomplete user-defined types, then update the guideline wording so both cases are addressed. Done means the recommendations no longer overstate what can be determined for incomplete types.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- cpp
- Domain
- documentation
- Issue type
- Documentation
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 38/100