[Bug python/31391] New: Incorrect FinishBreakpoint test

[Bug python/31391] New: Incorrect FinishBreakpoint test

[tromey at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=31391

            Bug ID: 31391
           Summary: Incorrect FinishBreakpoint test
           Product: gdb
           Version: HEAD
            Status: NEW
          Severity: normal
          Priority: P2
         Component: python
          Assignee: unassigned at sourceware dot org
          Reporter: tromey at sourceware dot org
  Target Milestone: ---

py-finishbreakpoint.exp does this:

    gdb_test "python print (finishbp_default.hit_count)" "1.*" "check finishBP
on default frame has been hit"

It is trying to check the hit count of this breakpoint.
However, the actual output is:

python print (finishbp_default.hit_count)
Traceback (most recent call last):
  File "<string>", line 1, in <module>
RuntimeError: Breakpoint 3 is invalid.
Error while executing Python code.


... which matches by mistake.
This came up in a patch series I'm working on.

I plan to kfail this but not close this bug; I think
this probably is a real problem of some sort.

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[Bug python/31391] Incorrect FinishBreakpoint test

[ssbssa at sourceware dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=31391

Hannes Domani <ssbssa at sourceware dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |ssbssa at sourceware dot org

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[Bug python/31391] Incorrect FinishBreakpoint test

[vries at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=31391

Tom de Vries <vries at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |vries at gcc dot gnu.org

--- Comment #1 from Tom de Vries <vries at gcc dot gnu.org> ---
(In reply to Tom Tromey from comment #0)
> py-finishbreakpoint.exp does this:
> 
>     gdb_test "python print (finishbp_default.hit_count)" "1.*" "check
> finishBP on default frame has been hit"
> 
> It is trying to check the hit count of this breakpoint.
> However, the actual output is:
> 
> python print (finishbp_default.hit_count)
> Traceback (most recent call last):
>   File "<string>", line 1, in <module>
> RuntimeError: Breakpoint 3 is invalid.
> Error while executing Python code.
> 
> 
> ... which matches by mistake.
> This came up in a patch series I'm working on.
> 
> I plan to kfail this but not close this bug; I think
> this probably is a real problem of some sort.

I think this may be the behaviour specified here (
https://sourceware.org/gdb/current/onlinedocs/gdb.html/Breakpoints-In-Python.html
):
...
The optional temporary argument makes the breakpoint a temporary breakpoint.
Temporary breakpoints are deleted after they have been hit. Any further access
to the Python breakpoint after it has been hit will result in a runtime error
(as that breakpoint has now been automatically deleted).
...

So AFAIU, this happens:
- finish breakpoints 3 and 4 are set at the same location
- a continue hits both finish breakpoints
- the hit_count is not available in either breakpoint, as per the doc, because
  both temporary breakpoints have been deleted.
- the return_value is available in both finish breakpoints, because it doesn't
  rely on accessing the underlying python breakpoint

I think the test-case can be updated to accept the current behaviour, or we can
even remove the hit_count test.

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[Bug python/31391] Incorrect FinishBreakpoint test

[vries at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=31391

--- Comment #2 from Tom de Vries <vries at gcc dot gnu.org> ---
(In reply to Tom de Vries from comment #1)
> (In reply to Tom Tromey from comment #0)
> > py-finishbreakpoint.exp does this:
> > 
> >     gdb_test "python print (finishbp_default.hit_count)" "1.*" "check
> > finishBP on default frame has been hit"
> > 
> > It is trying to check the hit count of this breakpoint.
> > However, the actual output is:
> > 
> > python print (finishbp_default.hit_count)
> > Traceback (most recent call last):
> >   File "<string>", line 1, in <module>
> > RuntimeError: Breakpoint 3 is invalid.
> > Error while executing Python code.
> > 
> > 
> > ... which matches by mistake.
> > This came up in a patch series I'm working on.
> > 
> > I plan to kfail this but not close this bug; I think
> > this probably is a real problem of some sort.
> 
> I think this may be the behaviour specified here (
> https://sourceware.org/gdb/current/onlinedocs/gdb.html/Breakpoints-In-Python.
> html ):
> ...
> The optional temporary argument makes the breakpoint a temporary breakpoint.
> Temporary breakpoints are deleted after they have been hit. Any further
> access to the Python breakpoint after it has been hit will result in a
> runtime error (as that breakpoint has now been automatically deleted).
> ...
> 
> So AFAIU, this happens:
> - finish breakpoints 3 and 4 are set at the same location
> - a continue hits both finish breakpoints
> - the hit_count is not available in either breakpoint, as per the doc,
> because
>   both temporary breakpoints have been deleted.
> - the return_value is available in both finish breakpoints, because it
> doesn't
>   rely on accessing the underlying python breakpoint
> 
> I think the test-case can be updated to accept the current behaviour, or we
> can even remove the hit_count test.

I'll write a patch to this effect.

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[Bug python/31391] Incorrect FinishBreakpoint test

[vries at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=31391

--- Comment #3 from Tom de Vries <vries at gcc dot gnu.org> ---
(In reply to Tom de Vries from comment #2)
> I'll write a patch to this effect.

https://sourceware.org/pipermail/gdb-patches/2024-February/206853.html

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[Bug testsuite/31391] Incorrect FinishBreakpoint test

[vries at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=31391

Tom de Vries <vries at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|python                      |testsuite

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[Bug testsuite/31391] Incorrect FinishBreakpoint test

[cvs-commit at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=31391

--- Comment #4 from Sourceware Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Tom de Vries <vries@sourceware.org>:

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=cfb9cb1afd93dc71ea94ec7c7d9bfc0e43ace0bc

commit cfb9cb1afd93dc71ea94ec7c7d9bfc0e43ace0bc
Author: Tom de Vries <tdevries@suse.de>
Date:   Tue Feb 27 16:18:32 2024 +0100

    [gdb/testsuite] Fix test in gdb.python/py-finish-breakpoint.exp

    With test-case gdb.python/py-finish-breakpoint.exp, we run into:
    ...
    (gdb) python print (finishbp_default.hit_count)
    Traceback (most recent call last):
      File "<string>", line 1, in <module>
    RuntimeError: Breakpoint 3 is invalid.
    Error while executing Python code.
    (gdb) PASS: gdb.python/py-finish-breakpoint.exp: normal conditions: \
      check finishBP on default frame has been hit
    ...

    The test producing the pass is:
    ...
        gdb_test "python print (finishbp_default.hit_count)" "1.*" \
          "check finishBP on default frame has been hit"
    ...
    so the pass is produced because the 1 in "line 1" matches "1.*".

    Temporary breakpoints are removed when hit, and consequently accessing the
    hit_count attribute of a temporary python breakpoint (gdb.Breakpoint class)
is
    not possible, and as per spec we get a RuntimeError.

    So the RuntimeError is correct, and not specific to finish breakpoints.

    The test presumably attempts to match:
    ...
    (gdb) python print (finishbp_default.hit_count)
    1
    ...
    but most likely this output was never produced by any gdb version.

    Fix this by checking whether the finishbp_default breakpoint has hit by
    checking that finishbp_default.is_valid() is False.

    Tested on aarch64-linux.

    Approved-By: Tom Tromey <tom@tromey.com>

    PR testsuite/31391
    Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=31391

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[Bug testsuite/31391] Incorrect FinishBreakpoint test

[vries at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=31391

Tom de Vries <vries at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
   Target Milestone|---                         |15.1
         Resolution|---                         |FIXED

--- Comment #5 from Tom de Vries <vries at gcc dot gnu.org> ---
Fixed.

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