[Bug lto/104366] New: Regression: infinite loop in add_sibling_attributes

[Bug lto/104366] New: Regression: infinite loop in add_sibling_attributes

[bjorn@xn--rombobjrn-67a.se]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104366

            Bug ID: 104366
           Summary: Regression: infinite loop in add_sibling_attributes
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: lto
          Assignee: unassigned at gcc dot gnu.org
          Reporter: bjorn@xn--rombobjrn-67a.se
                CC: marxin at gcc dot gnu.org
  Target Milestone: ---

Created attachment 52339
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=52339&action=edit
source code for reproducing the problem

Compiling certain Ada source files with -g -flto -ffat-lto-objects triggers
what looks like infinite tail recursion in add_sibling_attributes in
dwarf2out.c. This began when GCC 12 landed in Fedora Rawhide. It does not
happen in GCC 11. Removing either -g, -flto or -ffat-lto-objects, or appending
-fno-lto, works around the problem.

It seems to be specific to 64-bit arches. Builds consistently continue running
indefinitely on all of Fedora's four 64-bit arches, but not on the two 32-bit
arches. I have investigated only on x86-64.

It's probably more or less specific to Ada, because otherwise it would have
caused lots and lots of failures in the recent Fedora mass rebuild.

# gcc --version
gcc (GCC) 12.0.1 20220129 (Red Hat 12.0.1-0)

# rpm -q gcc-gnat
gcc-gnat-12.0.1-0.4.fc36.x86_64

To reproduce:
gnatchop sources.ada
gcc -c -g -flto -ffat-lto-objects posix-process_environment.adb

[Bug lto/104366] [12 Regression] Regression: infinite loop in add_sibling_attributes

[marxin at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104366

Martin Liška <marxin at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2022-02-03
           Keywords|                            |needs-bisection,
                   |                            |needs-reduction
            Summary|Regression: infinite loop   |[12 Regression] Regression:
                   |in add_sibling_attributes   |infinite loop in
                   |                            |add_sibling_attributes
     Ever confirmed|0                           |1

--- Comment #1 from Martin Liška <marxin at gcc dot gnu.org> ---
Reproduced, bisecting that right now.

[Bug lto/104366] [12 Regression] Regression: infinite loop in add_sibling_attributes

[marxin at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104366

Martin Liška <marxin at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|needs-bisection             |
                 CC|                            |ebotcazou at gcc dot gnu.org

--- Comment #2 from Martin Liška <marxin at gcc dot gnu.org> ---
Started with r12-3383-g81e9178fe7f8bae4609619b1195765b14eef35b7, before the
revision it was affected by the ICE mentioned in PR101947.

[Bug lto/104366] [12 Regression] Regression: infinite loop in add_sibling_attributes

[marxin at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104366

--- Comment #3 from Martin Liška <marxin at gcc dot gnu.org> ---
Created attachment 52342
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=52342&action=edit
Reduced test-case

[Bug lto/104366] [12 Regression] Regression: infinite loop in add_sibling_attributes

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104366

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |12.0
           Keywords|                            |compile-time-hog

[Bug debug/104366] [12 Regression] Regression: infinite loop in add_sibling_attributes

[ebotcazou at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104366

Eric Botcazou <ebotcazou at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
           Assignee|unassigned at gcc dot gnu.org      |ebotcazou at gcc dot gnu.org

--- Comment #4 from Eric Botcazou <ebotcazou at gcc dot gnu.org> ---
Fixing.

[Bug debug/104366] [12 Regression] Regression: infinite loop in add_sibling_attributes

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104366

--- Comment #5 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Eric Botcazou <ebotcazou@gcc.gnu.org>:

https://gcc.gnu.org/g:38948b77dbc16f4c6cf6cff8661bab699b306f03

commit r12-7049-g38948b77dbc16f4c6cf6cff8661bab699b306f03
Author: Eric Botcazou <ebotcazou@adacore.com>
Date:   Fri Feb 4 12:07:46 2022 +0100

    Empty the base_types vector before (re)populating it

    Otherwise Bad Things happen when it is populated several times.

    gcc/
            PR debug/104366
            * dwarf2out.cc (dwarf2out_finish): Empty base_types.
            (dwarf2out_early_finish): Likewise.

[Bug debug/104366] [12 Regression] Regression: infinite loop in add_sibling_attributes

[ebotcazou at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104366

Eric Botcazou <ebotcazou at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|---                         |FIXED

--- Comment #6 from Eric Botcazou <ebotcazou at gcc dot gnu.org> ---
Thanks for reporting the problem.