Arguments evaluation order in a function call is not specified:
- Before C++17, the evaluation of each argument was unsequenced with the evaluation of other arguments, which can lead to undefined behavior if
the same value is modified in several arguments,
- After C++17, it is sequenced, but in an unspecified order: the behavior is not longer undefined, but the values passed to the function will be
non portable.
Both cases should be avoided, because the code will probably not be what was expected.
Noncompliant code example
void f(int i, int j);
void g() {
int i = 0;
f(++i, ++i); // Noncompliant, the call could either be f(1,2) or f(2,1) (since C++17) or undefined behavior (before C++17)
}
Exceptions
This rule does not apply to overloaded operators because they respect the sequencing order rules of the operator they overload (since C++17).
