[Bug python/34485] [gdb/python] gdbpy_initialize_gdb_readline misses error handling

https://sourceware.org/bugzilla/show_bug.cgi?id=34485

--- Comment #3 from Sourceware Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Tom de Vries <[email protected]>:

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=25f1035f403c929a38d822f0525ec1bb180fffb5

commit 25f1035f403c929a38d822f0525ec1bb180fffb5
Author: Tom de Vries <[email protected]>
Date:   Wed Aug 12 23:11:46 2026 +0200

    [gdb/python] Handle error in gdbpy_initialize_gdb_readline

    On Fedora Rawhide aarch64-linux, with test-case
gdb.python/py-failed-init.exp
    I ran into:
    ...
    builtin_spawn $build/gdb/gdb -nw -nx -q -iex set height 0 -iex set width 0
\
      -data-directory $build/gdb/data-directory -iex set interactive-mode on
    WARN: Could not find the standard library directory! The Python 'home' \
      directory was set to 'foo', is this correct?
    Error occurred computing Python error message.
    $build/gdb/gdb: warning:
    Could not load the Python gdb module from
`$build/gdb/data-directory/python'.
    Limited Python support is available from the _gdb module.
    Suggest passing --data-directory=/path/to/gdb/data-directory.
    (gdb) set height 0
    (gdb) set width 0
    (gdb) dir
    Reinitialize source path to empty? (y or n) y
    Source directories searched: $cdir:$cwd
    (gdb) dir $src/gdb/testsuite/gdb.python
    Source directories searched: $src/gdb/testsuite/gdb.python:$cdir:$cwd
    (gdb) python print (1)
    1
    (gdb) FAIL: $exp: gdb-command<python print (1)>
    quit
    Exception ignored on threading shutdown:
    Traceback (most recent call last):
      File "<string>", line 2, in <module>
    ModuleNotFoundError: No module named 'importlib'
    PASS: $exp: quit
    ...

    The test-case tries to break python:
    ...
    save_vars { env(PYTHONHOME) } {
        setenv PYTHONHOME foo
        clean_restart
    }
    ...
    enough to get it to this point:
    ...
    gdb_test "python print (1)" \
        "Python not initialized"
    ...
    but apparently, that doesn't work anymore in this python version:
    ...
    $ python --version
    Python 3.15.0b4
    ...

    The test-case needs updating, and I've submitted a testsuite patch [1] for
    that.

    The next question is why we're seeing a ModuleNotFoundError on quit.

    I investigated this, and found that it originates from
    gdbpy_initialize_gdb_readline, where we do:
    ...
       if (eval_python_command (code, Py_file_input) == 0)
        PyOS_ReadlineFunctionPointer = gdbpy_readline_wrapper;
    ...
    but don't report and reset the python error state, so instead the error is
    reported by Py_Finalize.

    Fix this by:
    - making sure that the error is reported immediately, though in the form of
a
      warning rather than an error, and
    - disabling the python-interactive command if gdbpy_initialize_gdb_readline
      fails, to avoid broken readline behavior in a python-interactive session.

    Also make the test-case a bit stricter by checking that there's no output
when
    quitting.

    Tested on aarch64-linux.

    Approved-By: Tom Tromey <[email protected]>

    Changes in v2:
    - use gdbpy_print_stack instead of PyErr_Print/PyErr_Clear
    - Fix error/warning message by ensure that command name is double-quoted
and
      displayed using command_style

    Versions:
    - v1 https://sourceware.org/pipermail/gdb-patches/2026-August/229261.html

    Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=34485

    [1] https://sourceware.org/pipermail/gdb-patches/2026-August/229193.html

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