[sjolsen]

>the function as you wrote, when used in the expression (getColor() == getColor()), results in undefined behavior

In C++14 (and I believe C++11), this is not correct. Specifically, §1.9/15 says, "Every evaluation in the calling function (including other function calls) that is not otherwise specifically sequenced before or after the execution of the body of the called function is indeterminately sequenced with respect to the execution of the called function;" this sentence is marked with a note that reads, "In other words, function executions do not interleave with each other."

Item 4 under the "Sequence point rules" section on the page you linked says basically the same thing. I haven't looked at the C++98 standard, but I imagine it allows this, too.

The two calls to "getColor" are indeterminately sequenced. As a result, the behaviour of evaluating "(getColor() == getColor())" is merely unspecified, not undefined. In fact, the behaviour is guaranteed to be equivalent to one of the possible orderings (§1.9/13: "Evaluations A and B are indeterminately sequenced when either A is sequenced before B or B is sequenced before A, but it is unspecified which").

[anuragbiyani]

Thanks for correcting me sjolsen. You are right, the behavior is unspecified only.

I added a StackOverflow question (http://stackoverflow.com/questions/28816936/is-the-value-of-...) to increase the chances of someone being able to find (hopefully authoritative) information when searching for it.