Warnings for partially-unused structured bindings in C++26 mode

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Project / Subsystem

gcc / gcc

Date

2026-05-12

Proposer

Ionuț Nicula <nicula@nicula.xyz>

Source type

public_inbox

Consensus

Proposed

Sentiment

—/10

Technical tradeoffs

• Requires C++26 mode to avoid being unergonomic.
• May increase the number of warnings, requiring developers to add `_` placeholders.

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All attributes

project: gcc
subsystem: gcc
patch_id: —
discussion_id: IwntDp_Q1VxRwhn7aMzNxnY2SVNNCEI8BMw2bMGfoymG74jx1ONjefmAtoNwjrkk2xcpHC7nBhKor_UBDinXr4qGnWi5pbKCkaK4G1RRzfQ=@nicula.xyz
source_type: public_inbox
title: Warnings for partially-unused structured bindings in C++26 mode
headline: Propose warnings for partially-unused structured bindings in C++26.
tldr: In C++26, enable `-Wunused` warnings for unused variables in structured bindings, now that unnamed placeholders are available.
proposer: Ionuț Nicula <nicula@nicula.xyz>
consensus: Proposed
outcome: proposed
sentiment_score: —
technical_tradeoffs: • Requires C++26 mode to avoid being unergonomic.
• May increase the number of warnings, requiring developers to add `_` placeholders.
series_id: —
series_role: standalone
series_parts: []
tags: • gcc
• c++
• warnings
• structured bindings
• unused variables
url: https://inbox.sourceware.org/gcc/IwntDp_Q1VxRwhn7aMzNxnY2SVNNCEI8BMw2bMGfoymG74jx1ONjefmAtoNwjrkk2xcpHC7nBhKor_UBDinXr4qGnWi5pbKCkaK4G1RRzfQ=@nicula.xyz
bugzilla_url: —
date: 2026-05-12T00:00:00.000Z

Warnings for partially-unused structured bindings in C++26 mode

Ionuț Nicula proposes enabling -Wunused warnings for structured bindings in C++26 mode when some sub-objects are unused. Before C++26, the lack of a placeholder variable (like _) made this awkward. This change could catch errors, particularly in loops where a variable is unintentionally unused due to copy-paste mistakes.