[Bug c++/91774] Assignment from return value of function to reference returned by function occasionally produces wrong results

[smartman1996 at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91774

--- Comment #3 from 이경룡 <smartman1996 at gmail dot com> ---
Oops. Sorry for the unclear explanation on the core. Forgive me.

the throw statement is not the bug itself but acted as a detector for the bug

line 28868 ~ 28925: Definition of Interpreter::Read()

line 28901 has statement:

        ListManager[probe].rchild = ListManager.Alloc();

which corresponds to the statement in the prior explanation:

        a[index].x = b.CalcFunc();

line 28557 ~ 28587: Definition of ListPocket::Alloc();

    {
    while(true){
        //something
    }

    //some calculation

    return allocIndex;
    }


Observing the bug with the testcase:

    among many times the ListPocket::Alloc() is invoked via
"ListManager.Alloc()"
    when the if statement with a for loop inside is triggered, the return value
is expected to be 30
                        (sorry for mistaking it as a while loop in the prior
explanation)

    the problem is that
    the return value of "ListManager.Alloc()" is not properly assigned into the
reference "ListManager[probe].rchild"
    In fact, the gdb shows that the return value is 30(even immediately after
the return)
    and using std::cout to print out the value reports as 30 inside and outside
the function prints 30.

    the cout part was disabled by the preprocessor and cannot be seen.

    i.e. ListManager[probe].rchild remains 29 (it was formerly 29)

the equivalent statement that works well is:

    {
        auto temp = ListManager.Alloc();
        ListManager[probe].rchild = temp;
        }

Note: sorry for the source reduction being late.