units ships debugger visualizers so that a quantity displays as its value and abbreviation — 5 m, 3 s — instead of an opaque object with an internal _linearized_value member: a natvis for the Visual Studio (MSVC) debugger, and an LLDB formatter for LLDB and its front-ends (CLion, Xcode, the VS Code CodeLLDB extension). The visualizer changes only the debugger display, never the program's behavior.

What you get

Without the visualizer, a meters<double> in the Watch or Locals window shows as a struct with a floating-point member. With it, the same quantity shows as its natural rendering:

distance 5 m meters<double>

elapsed 3 s seconds<double>

Both visualizers are general by design: a single set of wildcard rules covers every unit type — length, time, frequency, compound, dimensionless, decibel — with no unit name enumerated anywhere. A named unit (a class deriving from units::unit<...>) is rendered through its base, so meters<double> shows as 5 m too.

Visual Studio (natvis)

The file natvis/units.natvis is attached to the units CMake interface target and installed with the package. When you link units::units (see CMake integration) under MSVC, Visual Studio picks it up automatically for that target — no project setting, no manual "add existing item."

If you consume the headers without CMake, add the file to your solution manually: place units.natvis in a location Visual Studio scans (for example USERPROFILE%\Documents\Visual Studio 20xx\Visualizers\) or add it to your project.

LLDB (and CLion / Xcode / CodeLLDB)

The file natvis/units_lldb.py is an LLDB summary provider. Load it into a debug session, or once from your ~/.lldbinit:

command script import /path/to/units/natvis/units_lldb.py

A quantity then summarizes as its value and abbreviation:

(lldb) frame variable distance

(units::length::meters<double>) distance = 5 m

The abbreviation (m, s, Hz, …) is read by evaluating the unit's abbreviation() on a live process; where evaluation is unavailable (a core file, a heavily optimized build) the summary falls back to the conversion-factor tag name in brackets, so it is always present and readable. Front-ends built on LLDB — CLion, Xcode, and the VS Code CodeLLDB extension — pick up the same formatter; point their "LLDB init" setting at the command script import line above.

Note — the visualizers change only the debugger display, never program behavior. At run time the ordinary operator<< rendering (std::cout << distance; → 5 m) serves the same purpose on every compiler.