[Bug debug/90574] [gdb] gdb wrongly stopped at a breakpoint in an unexecuted line of code

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90574

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |wrong-code, wrong-debug
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2019-05-23
                 CC|                            |rguenth at gcc dot gnu.org
     Ever confirmed|0                           |1

--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
We somehow build a broken(?) CFG from the start:

;;   basic block 2, loop depth 0
;;    pred:       ENTRY
  if (argc == 0)
;;    succ:       3

;;   basic block 3, loop depth 0
;;    pred:       2
label:
  if (argc == 1)
    goto <bb 4>; [INV]
  else
    goto <bb 5>; [INV]

see how BB2 only has a single outgoing edge.  CFG cleanup fixes this for us.

.gimple has

  [t.c:2:1] {
    void label = <<< error >>>;

    [t.c:3:6] if (argc == 0) goto <D.1912>; else goto <D.1913>;
    <D.1912>:
    [t.c:4:5] {
      int * ptr;

      [t.c:6:1] label:
    }
    <D.1913>:
    [t.c:10:6] if (argc == 1) goto <D.1914>; else goto <D.1915>;

so that looks good, likewise .lower:

  [t.c:3:6] if (argc == 0) goto <D.1912>; else goto <D.1913>;
  <D.1912>:
  [t.c:6:1] label:
  <D.1913>:
  [t.c:10:6] if (argc == 1) goto <D.1914>; else goto <D.1915>;

iff we'd elide an empty block as having no side-effects we would have
deleted the label.

Thus confirmed as CFG build bug.