ISO/IEC TS 19841:2015

Overview

ISO/IEC TS 19841:2015 - Technical Specification for C++ Extensions for Transactional Memory is an informative (non‑normative) Technical Specification that describes proposed extensions to the C++ language and standard library to support Transactional Memory (TM). Written as a set of changes against the International Standard ISO/IEC 14882 (C++), the document specifies new syntactic forms and library modifications that enable programmers and implementers to express transactions, transaction-safety, and related runtime behavior. It is intended to document existing practice, provide guidance to vendors, and inform potential future standardization - not to introduce mandatory changes to the C++ standard.

Key topics and technical requirements

• Language extensions and syntax: The TS describes new syntactic constructs (presented as modifications to ISO/IEC 14882) to express transactional regions and related constructs.
• Statements and control: Entries in the table of contents reference constructs such as synchronized statement and atomic statement, showing the TS addresses transactional control flow and jump/exception interactions inside transactions.
• Transaction-safety and conversions: Sections like Transaction-safety conversion and transaction-safe function define how code and functions are categorized or converted with respect to transactional execution.
• Library support: The TS adds or modifies library components for transactional use, e.g. tx_exception (transaction exception type), and introduces requirements for transaction safety within the C++ library.
• Diagnostics and runtime: Coverage includes exception handling, diagnostics, and runtime support relevant to transactions (throwing/handling exceptions inside transactional contexts).
• Implementation guidance: Clauses on implementation compliance, feature testing, and conforming implementations guide compiler and library vendors on how to provide and test TM features.
• Informative nature: The document uses explicit edit instructions and highlights changes against ISO/IEC 14882; it is advisory and documents practices that may or may not become part of a future C++ standard.

Applications and who uses it

• Compiler and toolchain vendors - to prototype and implement TM language extensions and provide transaction-aware optimizations.
• Standard library implementers - to adapt containers, allocators, and exception types for transactional safety.
• Systems and concurrent software developers - to design lock‑free or optimistic concurrency using transactional constructs for performance and scalability.
• Research and performance engineering teams - to evaluate transactional memory semantics, performance trade‑offs, and language interactions.
• Library authors - to create transaction-aware libraries (memory, synchronization, utilities) consistent with proposed C++ TM guidance.

Related standards

• ISO/IEC 14882 (C++) - the International Standard that provides the base language rules and is the reference document against which TS 19841 is written.

Keywords: ISO/IEC TS 19841:2015, C++, Transactional Memory, transaction‑safety, synchronized statement, atomic statement, tx_exception, C++ language extensions, transactional library support.