C++26 Oxford Variadic Comma: How a Deprecated Token Becomes a Breaking Change

A Sandor Dargo blog post on C++26 explores the Oxford Variadic Comma deprecation, a change that makes the trailing comma before '...' in variadic function declarations a deprecated extension and eventually a compile error, closing a long-standing syntactic inconsistency in the C++ standard. The change affects legacy C-style variadic function signatures like foo(int, ...) vs foo(int ...) and requires code audits for any codebase using the deprecated form. The post received 99 points on Hacker News, suggesting broad developer awareness of the breaking change risk in existing C++ codebases.

Key Takeaways

• C++26 deprecates the trailing comma-before-ellipsis in variadic function declarations: foo(int, ...) → deprecated, foo(int ...) → standard
• Adopted in the C++26 standard cycle; affects any existing C-style variadic function signature using the deprecated form
• Sandor Dargo post at sandordargo.com/blog/2026/03/11; 99 HN points indicates widespread C++ community interest

Original source: Sandor Dargo Blog / Hacker News