113 lines
3.8 KiB
Markdown
113 lines
3.8 KiB
Markdown
# Limitations
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## Nameof
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* If argument does not have name, occurs the compilation error `"Expression does not have a name."`.
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## Nameof Type
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* To check is nameof type supported compiler use macro `NAMEOF_TYPE_SUPPORTED` or constexpr constant `nameof::is_nameof_type_supported`.
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* This library uses a compiler-specific hack (based on `__PRETTY_FUNCTION__` / `__FUNCSIG__`), which works on Clang >= 5, MSVC >= 15.3 and GCC >= 7.
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* Nameof type returns compiler-specific type name.
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* If argument does not have name, occurs the compilation error `"Expression does not have a name."`.
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## Nameof Enum
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* Do not use [nameof](https://github.com/Neargye/nameof) and [magic_enum](https://github.com/Neargye/magic_enum) in the same project to get enum name.
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* To check is nameof enum supported compiler use macro `NAMEOF_ENUM_SUPPORTED` or constexpr constant `nameof::is_nameof_enum_supported`.
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* This library uses a compiler-specific hack (based on `__PRETTY_FUNCTION__` / `__FUNCSIG__`), which works on Clang >= 5, MSVC >= 15.3 and GCC >= 9.
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* Enum can't reflect if the enum is a forward declaration.
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* Enum value must be in range `[NAMEOF_ENUM_RANGE_MIN, NAMEOF_ENUM_RANGE_MAX]`.
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* By default `NAMEOF_ENUM_RANGE_MIN = -128`, `NAMEOF_ENUM_RANGE_MAX = 128`.
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* `NAMEOF_ENUM_RANGE_MIN` must be less or equals than `0` and must be greater than `INT16_MIN`.
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* `NAMEOF_ENUM_RANGE_MAX` must be greater than `0` and must be less than `INT16_MAX`.
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* If need another range for all enum types by default, redefine the macro `NAMEOF_ENUM_RANGE_MIN` and `NAMEOF_ENUM_RANGE_MAX`.
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```cpp
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#define NAMEOF_ENUM_RANGE_MIN 0
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#define NAMEOF_ENUM_RANGE_MAX 256
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#include <nameof.hpp>
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```
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* 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 nameof`.
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```cpp
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#include <nameof.hpp>
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enum class number { one = 100, two = 200, three = 300 };
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namespace nameof {
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template <>
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struct enum_range<number> {
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static constexpr int min = 100;
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static constexpr int max = 300;
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};
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} // namespace nameof
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```
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* Nameof enum won't work if a value is aliased, work with enum-aliases is compiler-implementation-defined.
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```cpp
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enum ShapeKind {
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ConvexBegin = 0,
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Box = 0, // Won't work.
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Sphere = 1,
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ConvexEnd = 2,
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Donut = 2, // Won't work too.
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Banana = 3,
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COUNT = 4,
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};
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// nameof::nameof_enum(ShapeKind::Box) -> "ConvexBegin" or ""
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// NAMEOF_ENUM(ShapeKind::Box) -> "ConvexBegin" or ""
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```
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One of the possible workaround the issue:
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```cpp
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enum ShapeKind {
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// Convex shapes, see ConvexBegin and ConvexEnd below.
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Box = 0,
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Sphere = 1,
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// Non-convex shapes.
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Donut = 2,
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Banana = 3,
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COUNT = Banana + 1,
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// Non-reflected aliases.
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ConvexBegin = Box,
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ConvexEnd = Sphere + 1,
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};
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// nameof::nameof_enum(ShapeKind::Box) -> "Box"
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// NAMEOF_ENUM(ShapeKind::Box) -> "Box"
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// Non-reflected aliases.
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// nameof::nameof_enum(ShapeKind::ConvexBegin) -> "Box"
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// NAMEOF_ENUM(ShapeKind::ConvexBegin) -> "Box"
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```
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* If you hit a message like this:
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```text
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[...]
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note: constexpr evaluation hit maximum step limit; possible infinite loop?
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```
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Change the limit for the number of constexpr evaluated:
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* MSVC `/constexpr:depthN`, `/constexpr:stepsN` <https://docs.microsoft.com/en-us/cpp/build/reference/constexpr-control-constexpr-evaluation>
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* Clang `-fconstexpr-depth=N`, `-fconstexpr-steps=N` <https://clang.llvm.org/docs/UsersManual.html#controlling-implementation-limits>
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* 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>
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* Intellisense Visual Studio may have some problems analyzing `nameof`.
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