C++26 release faces delay after ISO ballot rejects draft over Contracts

C++26 may miss its expected release date after an ISO ballot rejected its draft, with a dispute over the proposed Contracts feature a major reason for opposition. The disagreement has exposed tensions among C++ maintainers over how to balance added safety checks against complexity and the language’s performance priorities.

Contracts let developers specify conditions that should hold before or after code runs, and assertions that check those conditions. The October ballot recorded 13 votes in favour, 9 against and 12 abstentions; ISO rules require negative votes to be no more than 25 per cent. Bjarne Stroustrup and colleagues argue the proposal is rushed and overly complex, while supporters say it has been considered for years and that returning the draft is part of the standards process. A delay could mean the version is informally called C++27.