On 04/02/2021 21:08, AJ D via Gcc wrote: > Isn't comma operator suppose to honor left-to-right associativity? > > When I try it on this test case, it exhibits right-to-left associativity.
You are not talking about associativity - you are talking about evaluation order. (The two things are often mixed up.) For the built-in comma operator, you get guaranteed order of evaluation (or more precisely, guaranteed order of visible side-effects). But for a user-defined comma operator, you do not - until C++17, which has guaranteed evaluation ordering in some circumstances. See <https://en.cppreference.com/w/cpp/language/operator_other> (it's easier to read than the C++ standards). Try your test again with "-std=c++17" or "-std=g++17" - if the order is still reversed, it's a gcc bug (AFAICS). But for standards prior to C++17, the ordering is unspecified for user-defined comma operators. This is not unlike the difference between the built-in logic operators && and ||, which are guaranteed short-circuiting, while user-defined overloads are not. And for arithmetic operators, you don't get integer promotion, automatic conversion to a common type, etc. Basically, the user-defined operators are just syntactic sugar for a function call - they don't have the "magic" features of the real operators. David
