[Bug c/99784] New: `labels as values`can point to the wrong spot after optimization

[Bug c/99784] New: `labels as values`can point to the wrong spot after optimization

[mh+gcc at glandium dot org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99784

            Bug ID: 99784
           Summary: `labels as values`can point to the wrong spot after
                    optimization
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: mh+gcc at glandium dot org
  Target Milestone: ---

Reduced testcase:
```
extern void bar();
extern void qux(void*);
void foo() {
    bar();
here:
    qux(&&here);
}
```
Resulting code at -O2:
```
foo():
.LFB0:
.L2:
        sub     rsp, 8
        call    bar()
.LVL0:
        mov     edi, OFFSET FLAT:.L2
        add     rsp, 8
        jmp     qux(void*)
```

IOW, the pointer that qux gets is that of a location before the call to bar!

[Bug c/99784] `labels as values`can point to the wrong spot after optimization

[mh+gcc at glandium dot org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99784

--- Comment #1 from Mike Hommey <mh+gcc at glandium dot org> ---
This is reproducible with all versions of GCC on godbolt, including trunk.

[Bug c/99784] `labels as values`can point to the wrong spot after optimization

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99784

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |DUPLICATE
             Status|UNCONFIRMED                 |RESOLVED

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Dup of bug 96956.  This is undefined.  See PR 96956 for the reason why.

*** This bug has been marked as a duplicate of bug 96956 ***

[Bug c/99784] `labels as values`can point to the wrong spot after optimization

[mh+gcc at glandium dot org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99784

--- Comment #3 from Mike Hommey <mh+gcc at glandium dot org> ---
PR 96956 only really talks about this: "You may not use this mechanism to jump
to code in a different function. If you do that, totally unpredictable things
happen.".
My testcase doesn't involve jumping to the address.