note: the ABI of passing union with ‘long double’ has changed in GCC 4.4

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Project / Subsystem

gcc / gcc

Date

2026-09-14

Proposer

Jonathan Grant <jgrantonline@gmail.com>

Source type

public_inbox

Consensus

Proposed

Sentiment

—/10

Technical tradeoffs

• Maintaining backward compatibility and ABI stability versus cleaning up old diagnostic notes.
• The impact of removing a warning note on users who might still rely on the older ABI behavior or are unaware of the change.

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All attributes

project: gcc
subsystem: gcc
patch_id: —
discussion_id: 8361a782-d57d-4ad8-96dd-51fd426c512d@gmail.com
source_type: public_inbox
title: note: the ABI of passing union with ‘long double’ has changed in GCC 4.4
headline: Revisit ABI change note for union with long double
tldr: Question if GCC's ABI change note for union/long double is still relevant.
proposer: Jonathan Grant <jgrantonline@gmail.com>
consensus: Proposed
outcome: proposed
sentiment_score: —
technical_tradeoffs: • Maintaining backward compatibility and ABI stability versus cleaning up old diagnostic notes.
• The impact of removing a warning note on users who might still rely on the older ABI behavior or are unaware of the change.
series_id: —
series_role: standalone
series_parts: []
tags: • gcc
• abi
• warning
• long double
• union
url: https://inbox.sourceware.org/gcc/8361a782-d57d-4ad8-96dd-51fd426c512d@gmail.com
bugzilla_url: —
date: 2026-09-14T00:00:00.000Z

note: the ABI of passing union with ‘long double’ has changed in GCC 4.4

The author questions whether a compiler note, originally added to inform about an ABI change in GCC 4.4 concerning unions with long double, is still necessary given GCC’s current version (16). They provide a Godbolt link demonstrating the note’s appearance and ask if it can be removed to avoid requiring pragmas or -Wno-psabi flags. A related Bugzilla entry (118676) is also mentioned.