case112 — inline namespace version bumped (BREAKING)

Field	Value
Verdict	🔴 BREAKING
Category	Breaking
Platforms	Linux, macOS, Windows
Flags	ABI break
Detected ChangeKinds	inline_namespace_version_bumped
Source files	browse on GitHub

What this case demonstrates

A library uses a versioned inline namespace (inline namespace _V1) to manage ABI evolution. Between v1 and v2 the version segment is bumped to _V2. Source still compiles, but every freshly built TU emits a different mangled symbol — old and new TUs of the same program ODR- violate when linked together.

v1 declares	v2 declares
lib::_V1::sort, lib::_V1::unique (inline)	lib::_V2::sort, lib::_V2::unique (inline)

Why a dedicated detector

The existing INLINE_NAMESPACE_MOVED detector is symbol-table driven and requires ≥2 mangled-symbol moves. It works for built shared libraries but misses:

• header-only / template libraries that ship no .so
• single-symbol bumps
• pure declaration-level snapshots (castxml header dumps)

INLINE_NAMESPACE_VERSION_BUMPED fires from declared qualified names alone, so it catches the bump even on header-only inputs and on a single declaration.

Expected verdict

BREAKING — mangled names change, so any program that mixes old and new TUs at link or load time is broken.

---

Source files

• CMakeLists.txt
• app.cpp
• v1.cpp
• v1.h
• v2.cpp
• v2.h

See also: Examples overview · All BREAKING cases · Category: Breaking.