Re: PING: [PATCH v4] fixed inherit_abstract_dies infinite recursive call

[Doug Evans <xdje42 at gmail dot com>]

On Mon, Feb 10, 2014 at 6:28 AM, Joel Brobecker <brobecker@adacore.com> wrote:
> Ping!
>
> It would be interesting to have a formal review of this patch,
> to know if it is an acceptable fix or not.  If not, I can schedule
> some time to follow any recommendation that might come out of
> this review.
>
> Thank you!
>
> On Tue, Jan 28, 2014 at 04:06:00PM +0400, Joel Brobecker wrote:
>> >      > btw, do you have a copyright assignment on file?
>> >      > This change feels small enough to me to not need one,
>> >      > but it's not clear.
>> >
>> >      I am a Chinese guy,and Chinese have not clue about the copyright.
>> >      (A joke.I don't need copyright.)
>>
>> It's actually not for your personal benefit, but rather to help the FSF
>> enforce the GPL license on the code you are contributing, thus helping
>> it defend the freedom of our collective code. See:
>> http://www.gnu.org/licenses/why-assign.html
>>
>> > >>    Please Joel Brobecker <brobecker@adacore.com> helps with the testcases.
>>
>> Attached is a testcase that causes the debugger to crash on
>> x86_64-linux. It should work on all ELF targets.
>>
>> A plea to the dwarf2read.c gurus:
>>
>> Would it be possible to take a look at this patch, to see if it is
>> going in the right direction? Otherwise, I'll take a deeper look,
>> and see if I can solve it better. Intuitively, I think it may work,
>> but almost as a side-effect. Could the recursion check introduced
>> here do more than what we'd want to, for instance?
>>
>> Thanks!
>>
>> > >>>     The c++ code causing the problem is:
>> > >>>
>> > >>>         // Integer variants of certain metrics, used for HTML rendering.
>> > >>>         int ascent(FontBaseline baselineType = AlphabeticBaseline) const
>> > >>>         {
>> > >>>             if (baselineType == AlphabeticBaseline)
>> > >>>                 return lroundf(m_ascent);
>> > >>>             return height() - height() / 2;
>> > >>>         }
>> > >>>
>> > >>>         int height(FontBaseline baselineType = AlphabeticBaseline) const
>> > >>>         {
>> > >>>             return ascent(baselineType) + descent(baselineType);
>> > >>>         }
>> > >>>
>> > >>>     As you can see,ascent(0x5816d55) calls height(0x5812c1b),and height calls
>> > >>>     ascent(0x5816d55) recursivly.And the compiler  generates these dwarf code
>> > >>>     representing this relationship preciously.
>> > >>>
>> > >>>     A dwarf die may have the following relationship:
>> > >>>     564860c<-----------------------------
>> > >>>       |                                 |
>> > >>>       |(abstract origin)                |
>> > >>>       |                                 |
>> > >>>       V                                 |
>> > >>>     5816d55                             | (abstract origin)
>> > >>>       |                                 |
>> > >>>       |(child)                          |
>> > >>>       |                                 |
>> > >>>       V                                 |
>> > >>>       ...                               |
>> > >>>     5812c34------------------------------
>> > >>>     So inherit_abstract_dies may results in infinite recursive call.
>> > >>>     A bit field call in_process has been add to struct die_info to fix this problem.
>> > >>>     process_die would first check if a die is in processing state, if so,just return.
>> > >>>     Then in_process bit is set.Before process_die returns,this bit field is unset.---
>> >  ChangeLog        |  4 ++++
>> >  gdb/dwarf2read.c | 20 ++++++++++++++++++++
>> >  2 files changed, 24 insertions(+)
>> >
>> > diff --git a/ChangeLog b/ChangeLog
>> > index 9b1cbfa..0098a72 100644
>> > --- a/ChangeLog
>> > +++ b/ChangeLog
>> > @@ -1,3 +1,7 @@
>> > +2013-01-20  lin zuojian  <manjian2006@gmail.com>
>> > +   * dwarf2read.c (struct die_info): New member in_process.
>> > +   (reset_die_in_process): New function.
>> > +   (process_die): Set it at the start, reset when returning.
>> >  2013-12-19  Keven Boell  <keven.boell@intel.com>
>> >
>> >     * cp-namespace.c (cp_lookup_nested_symbol): Enable
>> > diff --git a/gdb/dwarf2read.c b/gdb/dwarf2read.c
>> > index 7ca527d..ffedde5 100644
>> > --- a/gdb/dwarf2read.c
>> > +++ b/gdb/dwarf2read.c
>> > @@ -1225,6 +1225,9 @@ struct die_info
>> >         type derived from this DIE.  */
>> >      unsigned char building_fullname : 1;
>> >
>> > +    /* True if this die is in process.  */
>> > +    unsigned char in_process : 1;
>> > +
>> >      /* Abbrev number */
>> >      unsigned int abbrev;
>> >
>> > @@ -8008,11 +8011,27 @@ process_imported_unit_die (struct die_info *die, struct dwarf2_cu *cu)
>> >      }
>> >  }
>> >
>> > +/* Reset the in_process bit of a die.  */
>> > +
>> > +static void
>> > +reset_die_in_process (void *arg)
>> > +{
>> > +  struct die_info *die = arg;
>> > +  die->in_process = 0;
>> > +}
>> > +
>> >  /* Process a die and its children.  */
>> >
>> >  static void
>> >  process_die (struct die_info *die, struct dwarf2_cu *cu)
>> >  {
>> > +  struct cleanup *in_process;
>> > +
>> > +  /* Only process those not already in process.  */
>> > +  if (die->in_process)
>> > +    return;
>> > +  die->in_process = 1;
>> > +  in_process = make_cleanup (reset_die_in_process,die);
>> >    switch (die->tag)
>> >      {
>> >      case DW_TAG_padding:
>> > @@ -8100,6 +8119,7 @@ process_die (struct die_info *die, struct dwarf2_cu *cu)
>> >        new_symbol (die, NULL, cu);
>> >        break;
>> >      }
>> > +    do_cleanups (in_process);
>> >  }
>> >
>> >  /* DWARF name computation.  */
>> > --
>> > 1.8.3.2
>>

Hi.

How hard is it to write a testcase that triggers the problem?