mirror of
https://github.com/Neargye/magic_enum.git
synced 2026-01-10 23:44:29 +00:00
109 lines
3.8 KiB
Markdown
109 lines
3.8 KiB
Markdown
# Limitations
|
|
|
|
* This library uses a compiler-specific hack (based on `__PRETTY_FUNCTION__` / `__FUNCSIG__`), which works on Clang >= 5, MSVC >= 15.3 and GCC >= 9.
|
|
|
|
* To check is magic_enum supported compiler use macro `MAGIC_ENUM_SUPPORTED` or constexpr constant `magic_enum::is_magic_enum_supported`.</br>
|
|
If magic_enum used on unsupported compiler, occurs the compilation error. To suppress error define macro `MAGIC_ENUM_NO_CHECK_SUPPORT`.
|
|
|
|
* Enum can't reflect if the enum is a forward declaration.
|
|
|
|
* Enum value must be in range `[MAGIC_ENUM_RANGE_MIN, MAGIC_ENUM_RANGE_MAX]`.
|
|
|
|
* By default `MAGIC_ENUM_RANGE_MIN = -128`, `MAGIC_ENUM_RANGE_MAX = 128`.
|
|
|
|
* `MAGIC_ENUM_RANGE_MIN` must be less or equals than `0` and must be greater than `INT16_MIN`.
|
|
|
|
* `MAGIC_ENUM_RANGE_MAX` must be greater than `0` and must be less than `INT16_MAX`.
|
|
|
|
* If need another range for all enum types by default, redefine the macro `MAGIC_ENUM_RANGE_MIN` and `MAGIC_ENUM_RANGE_MAX`.
|
|
|
|
```cpp
|
|
#define MAGIC_ENUM_RANGE_MIN 0
|
|
#define MAGIC_ENUM_RANGE_MAX 256
|
|
#include <magic_enum.hpp>
|
|
```
|
|
|
|
* If need another range for specific enum type, add specialization `enum_range` for necessary enum type. Specialization of `enum_range` must be injected in `namespace magic_enum::customize`.
|
|
|
|
```cpp
|
|
#include <magic_enum.hpp>
|
|
|
|
enum class number { one = 100, two = 200, three = 300 };
|
|
|
|
namespace magic_enum::customize {
|
|
template <>
|
|
struct enum_range<number> {
|
|
static constexpr int min = 100; // Must be greater than `INT16_MIN`.
|
|
static constexpr int max = 300; // Must be less than `INT16_MAX`.
|
|
};
|
|
} // namespace magic_enum
|
|
```
|
|
|
|
* `magic_enum` [won't work if a value is aliased](https://github.com/Neargye/magic_enum/issues/68). Work with enum-aliases is compiler-implementation-defined.
|
|
|
|
```cpp
|
|
enum ShapeKind {
|
|
ConvexBegin = 0,
|
|
Box = 0, // Won't work.
|
|
Sphere = 1,
|
|
ConvexEnd = 2,
|
|
Donut = 2, // Won't work too.
|
|
Banana = 3,
|
|
COUNT = 4
|
|
};
|
|
// magic_enum::enum_cast<ShapeKind>("Box") -> nullopt
|
|
// magic_enum::enum_name(ShapeKind::Box) -> "ConvexBegin"
|
|
```
|
|
|
|
One of the possible workaround the issue:
|
|
|
|
```cpp
|
|
enum ShapeKind {
|
|
// Convex shapes, see ConvexBegin and ConvexEnd below.
|
|
Box = 0,
|
|
Sphere = 1,
|
|
|
|
// Non-convex shapes.
|
|
Donut = 2,
|
|
Banana = 3,
|
|
|
|
COUNT = Banana + 1,
|
|
|
|
// Non-reflected aliases.
|
|
ConvexBegin = Box,
|
|
ConvexEnd = Sphere + 1
|
|
};
|
|
// magic_enum::enum_cast<ShapeKind>("Box") -> ShapeKind::Box
|
|
// magic_enum::enum_name(ShapeKind::Box) -> "Box"
|
|
|
|
// Non-reflected aliases.
|
|
// magic_enum::enum_cast<ShapeKind>("ConvexBegin") -> nullopt
|
|
// magic_enum::enum_name(ShapeKind::ConvexBegin) -> "Box"
|
|
```
|
|
|
|
On some compiler enum-aliases not supported, [for example Visual Studio 2017](https://github.com/Neargye/magic_enum/issues/36), macro `MAGIC_ENUM_SUPPORTED_ALIASES` will be undefined.
|
|
|
|
```cpp
|
|
enum Number {
|
|
one = 1,
|
|
ONE = 1
|
|
};
|
|
// magic_enum::enum_cast<Number>("one") -> nullopt
|
|
// magic_enum::enum_name(Number::one) -> ""
|
|
// magic_enum::enum_cast<Number>("ONE") -> nullopt
|
|
// magic_enum::enum_name(Number::ONE) -> ""
|
|
```
|
|
|
|
* If you hit a message like this:
|
|
|
|
```text
|
|
[...]
|
|
note: constexpr evaluation hit maximum step limit; possible infinite loop?
|
|
```
|
|
|
|
Change the limit for the number of constexpr evaluated:
|
|
* MSVC `/constexpr:depthN`, `/constexpr:stepsN` <https://docs.microsoft.com/en-us/cpp/build/reference/constexpr-control-constexpr-evaluation>
|
|
* Clang `-fconstexpr-depth=N`, `-fconstexpr-steps=N` <https://clang.llvm.org/docs/UsersManual.html#controlling-implementation-limits>
|
|
* GCC `-fconstexpr-depth=N`, `-fconstexpr-loop-limit=N`, `-fconstexpr-ops-limit=N` <https://gcc.gnu.org/onlinedocs/gcc-9.2.0/gcc/C_002b_002b-Dialect-Options.html>
|
|
|
|
* Intellisense Visual Studio may have some problems analyzing `magic_enum`.
|