Landing: 9bbec965c9b7

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Project / Subsystem

gcc / ada

Date

2026-02-23

Author

Eric Botcazou

Commit

9bbec965c9b781b6e7733ff92012701b805ab084

Source

github

Perf win

Breaking

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All attributes

project: gcc
subsystem: ada
patch_id: —
commit_hash: 9bbec965c9b781b6e7733ff92012701b805ab084
source_type: github
headline: Raise Program_Error for 'Constrained attribute on unchecked union parameters
tldr: The Ada compiler now raises Program_Error for the 'Constrained attribute when applied to non-In formal parameters of unchecked union types.
author: Eric Botcazou
outcome: committed
performance_win: false
breaking_change: false
series_id: —
series_parts: []
tags: • ada
• unchecked union
• program_error
• gnat
discussion_id_link: —
bugzilla_pr: —
url: https://github.com/gcc-mirror/gcc/commit/9bbec965c9b781b6e7733ff92012701b805ab084
date: 2026-02-23T00:00:00.000Z

GNAT historically hasn’t added extra formal parameters alongside formal parameters of unchecked union types, preventing computation of the ‘Constrained attribute for In Out or Out formal parameters. The compiler now raises Program_Error in these cases to enforce correct usage and prevent unexpected behavior. This change affects code that uses unchecked unions with the ‘Constrained attribute.