Hi, Addition with numbers is commutative: a + b = b + a Therefore, the order does not matter if your two functions f() and g() return numbers. If you have + overloaded(*) to operate on objects which are not commutative under addition (e.g. strings) then I would avoid this type of construct, and build two operations instead of one to guarantee order. Something like this: x += f(); x += g(); (*) I know that's possible in C++, not sure if C does that. HTH, David Carter-Hitchin, GSD-Risk-IT, UBS Investment Bank On Mon, 29 Mar 2004 laura_rand@xxxxxxxxxxxxxxxxx wrote: > hi, all > > i could not find an answer to this question on the net so i'm posting it > here. > > as far as i know, the Ansi C standard does not specify the order of > evaluation of expression arguments. so if i wrote: > > x = f() + g() > > it would be up to the compiler whether f() or g() would be called first. > > my question is, does anybody know how does the current version of gcc choose > whether to call f() or > g() first? on which optimization options does this depend, if any? > > after making a few experiments, it looks like gcc usually does left-to-right > evaluation (first calls f() and then g()). so i would like to know in which > cases (if any) this would not be true. or if this information is not known > for the current version, then for any previous version would also be > appreciated. > > to clarify: i am not interested in the evaluation order of arguments to a > function call, or left vs right side of an assigment. also i am not interested > in expressions involving pre- or post- increment or decrement or anything > such. i understand that these may be a problem. so my question is only regarding > function calls in expressions with normal arithmetic (also pointer > arithmetic) and compare operators. > > laura > > -- > +++ NEU bei GMX und erstmalig in Deutschland: TÜV-geprüfter Virenschutz +++ > 100% Virenerkennung nach Wildlist. Infos: http://www.gmx.net/virenschutz >
