Undoc'd Feature?

[Wes Loewer]

(07-08-2022 03:15 AM)jte Wrote:  If one were to add a single character to the first line of the C++ code below, one would enter the land of undefined behaviour for versions of C++ before C++17:

Since it's only one character, I'm guessing it has something to do with making b a reference to a

Code:

int a = 0, &b = a;

I could see this potentially causing a problem with

Code:

b=a++;

This could be interpreted as either
1) evaluate a (5)
2) assign that value to a (since b refers to a) (a=5)
3) increment a, making a (and b) 6

or interpreted as
1) evaluate a (5)
2) increment a (a is now 6)
3) assigned the value in step 1 to a, so a is back to 5 again.

Am I on the right track?