Landing: 4e2b29c333fc

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Project / Subsystem

gcc / libstdc++

Date

2026-07-22

Author

Nathan Blackburn

Commit

4e2b29c333fcbead93b2911326cff4218d3c155c

Source

github

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Breaking

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All attributes

project: gcc
subsystem: libstdc++
patch_id: —
commit_hash: 4e2b29c333fcbead93b2911326cff4218d3c155c
source_type: github
headline: Libstdc++: Remove noexcept from basic_string instantiations.
tldr: Unconditional noexcept is removed from basic_string's default constructor instantiations, as it can throw.
author: Nathan Blackburn
outcome: committed
performance_win: false
breaking_change: false
series_id: —
series_parts: []
tags: • libstdc++
• string
• noexcept
• conformance
discussion_id_link: —
bugzilla_pr: —
url: https://github.com/gcc-mirror/gcc/commit/4e2b29c333fcbead93b2911326cff4218d3c155c
date: 2026-07-22T00:00:00.000Z

Explicit instantiations of std::basic_string’s default constructor in libstdc++ incorrectly declared themselves as noexcept. This commit removes the unconditional noexcept specification from both char and wchar_t instantiations, as the default constructor for the fully-dynamic COW (Copy-On-Write) string implementation can, in fact, throw exceptions. This resolves a conformance issue.