Quuxplusone added a comment.
> Any runtime penalty? (Usually compilers choose a faster underlying type for
> enums, not smaller)
> The decision is made in the header (so I think it will always be `int` until
> this doesn't fit). To decide what is faster the compiler would need to know
> all the usages. Which it can't.
Yes, Clang chooses `int` by default. In fact, C++11 and later //mandate// that
a new-style scoped enum `enum class Foo {` means the same thing as `enum class
Foo : int {` — see https://timsong-cpp.github.io/cppwp/n3337/dcl.enum#5 . For
unscoped old-style enums, Clang/GCC/MSVC all choose `int` by default,
//unless// `-fshort-enums` is passed on the command line and/or the enum is
annotated with `__attribute__((packed))`, in which case it chooses the smallest
possible type. `-fshort-enums` and `__attribute__((packed))` have no effect on
new-style scoped enums nor on enums with explicit underlying types.
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D120398/new/
https://reviews.llvm.org/D120398
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