stl_compat.md

stl_compat

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Header

#include <ext/stl_compat>

Overview

Centralizes feature detection and compatibility shims used throughout the library. Headers opt into required standard library features by defining CXX_USE_* macros before including this file.

Key APIs

• Feature macros indicate whether standard facilities are available or emulated.
• Fallback definitions cover selected C++11/C++14/C++17 utilities when older toolchains lack them.
• Loop, noexcept, constexpr, move, type-trait, and threading compatibility helpers are provided for internal headers.

Behavior Notes

• Most users include feature headers directly and do not need to include stl_compat themselves.
• The file is intentionally broad because this library supports old Visual Studio and Boost-assisted builds.

Extension Contract

• Treat CXX_USE_*, CXX_STD_*_NOT_SUPPORTED, and _EXT_* macros as compatibility controls for ext internals unless a feature page explicitly asks users to define one.
• Prefer adding feature detection in this header instead of scattering compiler checks across public APIs.
• Keep compatibility fallbacks behaviorally close to the standard facility they emulate, but document any observable differences on the feature page that exposes them.