Undoc'd Feature?

[toml_12953]

(07-09-2022 12:20 PM)RPNerd Wrote:  

(07-09-2022 05:15 AM)Wes Loewer Wrote:  I tried the following on several different C/C++ compilers

Code:

int a=5;
a = a++;
printf("%d\n",a);

and they all printed out 5, except for the Microsoft compiler which prints 6. They all claim to be C++20 compliant, so somebody's wrong.

I would contend that the Microsoft compiler is wrong and the others are correct.

The effect of:

Code:

a = a++

...should be:

1) Keep a record of the current value of 'a' as this is going to be the value of the expression 'a++'

2) Do a post-increment on 'a', so 'a' is now 6

3) Assign the value of the expression 'a++' retained in step 1 (i.e.: 5) to 'a'

Step 3 re-assigns 5 to a.

I'd think the sequence would be

1) store the current value of a (5) back in a
2) increment a

This would still give 5, though.