Using enums for storing bitflags in C++ is a bit troublesome, since once the enum values are ORed they loose their enum-type, which causes errors without explicit casting.
The accepted answer for this question suggests overloading the | operator:
FlagsSet operator|(FlagsSet a, FlagsSet b) { return FlagsSet(int(a) | int(b)); } I'd like to know if this method has any runtime implications?
Runtime implications in terms of correctness? No - this should be exactly what you want.
Runtime implications in terms of speed? I would expect any decent compiler to optimize this away properly to the minimal number of instructions for a release build (although you might want to add inline just to be sure).
inline: smart compilers will ignore the keyword and inline code at their discretion; it is generally useless to mark functions inline for performance reasons these days. There is, however, very much different reason to add inline, assuming the function is defined in a header file.It potentially does three copies and a function call, barring RVO, registers, and/or inlining optimizations.
Naked bitwise OR operations themselves usually decompose to a single processor instruction.
The code is correct.
The code will be the same speed as without type casts.
But whether the code is fast is irrelevant, because a type named 'FlagSet' will most probably be used in a context of conditionals test (-> "if (Flag)"), which is more of a hit to speed than a bit wise 'or' of two values of the size of a register.
use std::bitset for your bit flags... much simpler ;) or boost::dynamic_bitset.
vector<bool> which is nothing like a set of bit-flags.
inttounsigned- otherwise you're asking for other code to end up with sign-extension issues (bit flags are never signed! that would be insanely foolish).