Avoid a heap allocation on every legacy py::enum_ load #5860
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rwgk
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Oct 11, 2025
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Description
During development of #5800, I noticed that the native enum caster unnecessarily heap-allocates the fallback base caster if it needs to handle a load of a type that was exposed using the pre-v3
py::enum_rather thanpy::native_enum. Fix this.Since
enum_is a wrapper aroundclass_, a Python instance of a type exposed withenum_contains a [pointer to a] C++ enum object of appropriate type. It is therefore unnecessary to keep the type caster alive in order to preserve the referent of casts toconst EnumType&orEnumType*. The heap allocation previously used by the native enum caster was incurring a performance cost on loads without providing any reliability or clarity benefits.Suggested changelog entry:
Improve the performance of from-Python conversions of legacy pybind11 enum objects bound by
py::enum_.