New submission from Dave Malcolm <dmalc...@redhat.com>:
It's sometimes useful to be able to programatically inject a breakpoint when
debugging CPython.
For example, sometimes you want a conditional breakpoint, but the logic
involved is too complex to be expressed in the debugger (e.g. runtime
complexity of evaluating the conditional in the debugger process, or deficiency
of the debugger itself).
I'm attaching a patch which:
- adds a Py_BREAKPOINT macro to pyport.h This is available as a quick and
dirty way of hardcoding a breakpoint in code (e.g. in extension modules); so
that when you need to you can put of these in (perhaps guarded by C-level
conditionals):
if (complex_conditional()) {
Py_BREAKPOINT();
}
- when Py_BREAKPOINT is defined, adds a sys.breakpoint() method. This means
that you can add C-level breakpoints to Python scripts, perhaps guarded by
python-level conditionals:
if foo and bar and not baz:
sys.breakpoint()
Naturally this is highly system-dependent. Only tested on Linux (Fedora 13
x86_64 with gcc-4.4.4). The Windows implementation was copied from
http://bugs.python.org/issue8863 but I don't have a Windows box to test it on.
I note that the GLib library within GNOME has a similar idea with a
G_BREAKPOINT macro, which has accumulated a collection of platform-specific
logic:
http://git.gnome.org/browse/glib/tree/glib/gbacktrace.h
(unfortunately that's LGPLv2+ licensed)
Doesn't yet have a unit test.
Note that when running on Linux when _not_ under a debugger, the default for
SIGTRAP is to get a coredump:
Trace/breakpoint trap (core dumped)
so people should be strongly discouraged from adding these calls to their code.
----------
components: Interpreter Core, Library (Lib)
files: add-sys.breakpoint.patch
keywords: patch, patch
messages: 114301
nosy: dmalcolm, haypo
priority: normal
severity: normal
stage: patch review
status: open
title: RFE(patch): add Py_BREAKPOINT and sys.breakpoint hooks
type: feature request
versions: Python 3.2, Python 3.3
Added file: http://bugs.python.org/file18572/add-sys.breakpoint.patch
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<http://bugs.python.org/issue9635>
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