Landing: 8a3aa5492993
Project / Subsystem
gcc / c++/modules
Date
2026-06-05
Author
Patrick Palka
Commit
8a3aa549299337ffee8d808bf7d997b7cb1f99fe
Source
github
Perf win
Yes
Breaking
No
All attributes
- project
- gcc
- subsystem
- c++/modules
- patch_id
- —
- commit_hash
- 8a3aa549299337ffee8d808bf7d997b7cb1f99fe
- source_type
- github
- headline
- Disable dependent ADL inside C++ header units to improve stream-in performance.
- tldr
- Dependent Argument-Dependent Lookup (ADL) is now disabled within C++ header units to prevent significant slowdowns in module stream-in.
- author
- Patrick Palka
- outcome
- committed
- performance_win
- true
- breaking_change
- false
- series_id
- —
- series_parts
- []
- tags
-
- • c++
- • modules
- • performance
- • adl
- discussion_id_link
- —
- bugzilla_pr
- —
- date
- 2026-06-05T00:00:00.000Z
This commit disables dependent Argument-Dependent Lookup (ADL) when processing C++ header units. This change directly addresses a significant performance regression, roughly doubling the stream-in time for the std module when <bits/stdc++.h> is built as a header unit. Because header units do not discard or hide entities, dependent ADL is not strictly necessary in this context and its removal restores module stream-in performance to previous levels.