Limitations and Configuration

	Caution
	Recommended C++ Standards are C++17 and above. Library requires at least C++14! Pre C++14 compilers (C++11, C++03...) are not supported.

PFR library works with types that satisfy the requirements of SimpleAggregate: aggregate types without base classes, const fields, references, or C arrays:

struct simple_aggregate {  // SimpleAggregate
    std::string name;
    int age;
    boost::uuids::uuid uuid;
};

struct empty {             // SimpleAggregate
};

struct aggregate : empty { // not a SimpleAggregate
    std::string name;
    int age;
    boost::uuids::uuid uuid;
};

The library may work with aggregates that don't satisfy the requirements of SimpleAggregate, but the behavior tends to be non-portable.

Configuration Macro

By default PFR auto-detects your compiler abilities and automatically defines the configuration macro into appropriate values. If you wish to override that behavior, just define:

Table 1.2. Macros

Macro name	Effect
PFR_USE_CPP17	Define to `1` if you wish to override PFR choice and use C++17 structured bindings for reflection. Define to `0` to override PFR choice and disable C++17 structured bindings usage.
PFR_USE_LOOPHOLE	Define to `1` if you wish to override PFR choice and exploit CWG 2118 for reflection. Define to `0` to override PFR choice and disable CWG 2118 usage.
PFR_USE_STD_MAKE_INTEGRAL_SEQUENCE	Define to `0` if you are hit by the template instantiation depth issues with `std::make_integer_sequence` and wish to use PFR version of that metafunction. Define to `1` to override PFR detection logic.
PFR_HAS_GUARANTEED_COPY_ELISION	Define to `0` if your compiler does not implement C++17 guaranteed copy elision properly and fails to reflect aggregates with non-movable fields. Define to `1` to override PFR detection logic.
PFR_ENABLE_IMPLICIT_REFLECTION	Define to `0` if you are hit by lots of non-effective choices made by implicitly reflection. Define to `1` to override PFR detection logic.
PFR_ENABLED	On platforms where PFR is not supported, the `pfr/config.hpp` header defines the PFR_ENABLED macro equal to 0. Defining this macro as 0 before including the header disables the PFR library.

Details on Limitations

The PFRs reflection has some limitations that depend on a C++ Standard and compiler capabilities:

Static variables are ignored
T must be aggregate initializable without base classes
if T contains C arrays then the result of reflection may differ depending on the C++ version and library configuration
Additional limitations if PFR_USE_CPP17 == 0:
- Non of the member fields should have a template constructor from one parameter.
- Additional limitations if PFR_USE_LOOPHOLE == 0:
  - T must be constexpr aggregate initializable and all its fields must be constexpr default constructible
  - pfr::get, pfr::structure_to_tuple, pfr::structure_tie, pfr/core.hpp require T to be a POD type with built-in types only.