llvm/llvm-project

[-Wunsafe-buffer-usage] Warn about two-arg string view constructors

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#166,644 opened on Nov 5, 2025

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clang:diagnosticsgood first issue

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Description

The two-arg form of std::span<> will currently produce a warning when used along with the -Wunsafe-buffer-usage-in-container option, subject to heuristics that try to determine suspicious arguments.

The string view types, (actually std::basic_string_view<>) have the same issues as does std::span<> when used with a two-argument constructor.

Since the name of the -W flag says "container", I humbly propose covering this case under the same warning, and produce the same waring when encountered.

A small task is removing the specific mention of std::span<> from the diagnostic, expanding it to imply other containers.

Contributor guide

Research direction
Locate the diagnostic emitting the Wunsafe buffer usage warning for std::span two arg constructor. Extend it to also cover std::basic string view constructors. Update the warning message to refer to 'container' instead of 'std::span'.
Tech stack
cpp
Domain
developer experiencetooling
Issue type
Feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
2
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
C++Git
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
75