struct ara::core::is_nothrow_swappable

In module core of the AUTOSAR Adaptive Platform (release R25-11), the template structure ara::core::is_nothrow_swappable provides a compile-time utility that checks whether two instances of a type can be swapped without exceptions, analogous to std::is_nothrow_swappable in accordance with C++17 [meta.unary.prop]. It is primarily used in generic algorithms and data structures to safeguard exception-safe swaps via SFINAE or static assertions. Since evaluation is performed completely statically by the compiler, neither runtime resources nor dynamic errors are incurred. As an essential constraint, error-free checking requires that the passed data type is completely defined at the time of instantiation.

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Context

In the module core of the AUTOSAR Adaptive Platform (Release R25-11), the template structure ara::core::is_nothrow_swappable provides a meta-function utility for static type checking. Its semantic definition directly references std::is_nothrow_swappable according to the ISO C++17 standard ISO/IEC 14882:2017 (section [meta.unary.prop]). As a trait, it serves developers of generic components to query at compile time whether two lvalues of a concrete data type T can be swapped with each other without throwing exceptions.

In the architectural context, the trait primarily interacts with generic algorithms, containers, and utility functions of the AUTOSAR Core module as well as application-specific implementations. The check is typically expected to be utilized in generic library functions or data structures of the module to ensure exception-safe swap operations via SFINAE, static_assert, or conditional noexcept specifications. Question Q-2d97f825685fd7df (open) This check ensures that operations such as swapping buffer contents or states satisfy the requirements for robust and deterministic processes in the Adaptive ecosystem.

Lifecycle

Since ara::core::is_nothrow_swappable is a pure template metaprogramming structure, it has no classic runtime lifecycle. There are no instantiation phases, no dynamic memory allocations, and no destruction sequences in the executed application. The evaluation of properties is performed entirely statically by the compiler during the compilation process.

From this purely static nature also follows the absence of runtime states or state transitions. The trait is not subject to any concurrency restrictions, as querying type traits is thread-neutral and free of side effects. Presumably, analogously to the standard model, ara::core::is_nothrow_swappable inherits from std::integral_constant<bool, ...>, thereby providing the type constant value as well as corresponding conversion operators that are available as constants without runtime overhead. Question Q-2d4f07696ff1d090 (open)

Usage Path

The typical usage path of ara::core::is_nothrow_swappable is structured into defining a type to be checked, statically querying swappability, and controlling compile-time branching:

• Provision of the data type: A target type T is declared and ideally implements its own swap function marked as noexcept, or relies on element-wise swappable substructures.
• Static check: Within a generic context, the developer instantiates ara::core::is_nothrow_swappable<T> and reads the static boolean data member value.
• Conditional optimization or assertion: The result controls static_assert assertions, SFINAE overloads, or noexcept(...) clauses in user-defined swap operations.

Through this sequence, it can be guaranteed that swapping algorithms only provide an exception-safe guarantee to the outside if the underlying type T actually satisfies this condition.

Error Scenarios

Classic runtime errors, error codes, or exceptions do not occur when using ara::core::is_nothrow_swappable, as the construct is not executed at runtime. Error situations manifest themselves exclusively during compilation instead.

Interpretation: Types T that are incomplete at the time of instantiation (so-called incomplete types) are likely to lead to compiler errors, as the validity and exception safety of the swap expression requires a complete type definition. Question Q-e2785ad38b24b360 (open) Another error scenario arises when developers mistakenly assume that a type is non-throwing swappable, whereupon a static assertion (static_assert) deliberately aborts the compilation process in order to avert unexpected runtime risks.