Allow switching to pretty-printer when using `gdb`

[wooffie]

Can we remove If True: from gdb bindings?

I think it was created for future features, but it was 15 years ago.

Found 2 locations (not testcase for interpreter):

cpython/Tools/gdb/libpython.py

Line 1587 in 7ec1742

if True:

cpython/Tools/gdb/libpython.py

Line 1602 in 7ec1742

if True:

Additional information

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Reporter: Burkov Egor (eburkov@rvision.ru).

Organization: R-Vision (support@rvision.ru).

Linked PRs

• gh-129351: Allow switching to pretty-printer when using gdb #138169

[StanFromIreland]

The first one has a TODO

# TODO: repr() puts everything on one line; pformat can be nicer, but
# can lead to v.long results; this function isolates the choice

The second has nothing listed. I guess we can comment out the section for it.

[encukou]

These are undocumented and not very discoverable, but useful if you know about them.
I don't know if there's a good way to configure them (or ask GDB for longer output). Maybe we should just document them in the devguide.

[picnixz]

I don't know if there's a good way to configure them

An easy way to do it is by adding some environment variable. Alternatively, it's possible to create a new GDB command to switch between verbose and non-verbose output and modify

def pretty_printer_lookup(gdbval):
    type = gdbval.type.unqualified()
    if type.code != gdb.TYPE_CODE_PTR:
        return None

    type = type.target().unqualified()
    t = str(type)
    if t in ("PyObject", "PyFrameObject", "PyUnicodeObject", "wrapperobject"):
        return PyObjectPtrPrinter(gdbval)

so that the PyObjectPtrPrinter is constructed with a "verbose" style.