binutils-gdb/gdb/testsuite/gdb.python/py-bp-locations.exp
Simon Farre e5213e2c85 gdb/python: Add BreakpointLocation type
PR python/18385

v7:
This version addresses the issues pointed out by Tom.

Added nullchecks for Python object creations.

Changed from using PyLong_FromLong to the gdb_py-versions.

Re-factored some code to make it look more cohesive.

Also added the more safe Python reference count decrement PY_XDECREF,
even though the BreakpointLocation type is never instantiated by the
user (explicitly documented in the docs) decrementing < 0 is made
impossible with the safe call.

Tom pointed out that using the policy class explicitly to decrement a
reference counted object was not the way to go, so this has instead been
wrapped in a ref_ptr that handles that for us in blocpy_dealloc.

Moved macro from py-internal to py-breakpoint.c.

Renamed section at the bottom of commit message "Patch Description".

v6:
This version addresses the points Pedro gave in review to this patch.

Added the attributes `function`, `fullname` and `thread_groups`
as per request by Pedro with the argument that it more resembles the
output of the MI-command "-break-list".  Added documentation for these attributes.

Cleaned up left overs from copy+paste in test suite, removed hard coding
of line numbers where possible.

Refactored some code to use more c++-y style range for loops
wrt to breakpoint locations.

Changed terminology, naming was very inconsistent. Used a variety of "parent",
"owner". Now "owner" is the only term used, and the field in the
gdb_breakpoint_location_object now also called "owner".

v5:

Changes in response to review by Tom Tromey:
- Replaced manual INCREF/DECREF calls with
  gdbpy_ref ptrs in places where possible.
- Fixed non-gdb style conforming formatting
- Get parent of bploc increases ref count of parent.
- moved bploc Python definition to py-breakpoint.c

The INCREF of self in bppy_get_locations is due
to the individual locations holding a reference to
it's owner. This is decremented at de-alloc time.

The reason why this needs to be here is, if the user writes
for instance;

py loc = gdb.breakpoints()[X].locations[Y]

The breakpoint owner object is immediately going
out of scope (GC'd/dealloced), and the location
object requires it to be alive for as long as it is alive.

Thanks for your review, Tom!

v4:
Fixed remaining doc issues as per request
by Eli.

v3:
Rewritten commit message, shortened + reworded,
added tests.

Patch Description

Currently, the Python API lacks the ability to
query breakpoints for their installed locations,
and subsequently, can't query any information about them, or
enable/disable individual locations.

This patch solves this by adding Python type gdb.BreakpointLocation.
The type is never instantiated by the user of the Python API directly,
but is produced by the gdb.Breakpoint.locations attribute returning
a list of gdb.BreakpointLocation.

gdb.Breakpoint.locations:
The attribute for retrieving the currently installed breakpoint
locations for gdb.Breakpoint. Matches behavior of
the "info breakpoints" command in that it only
returns the last known or currently inserted breakpoint locations.

BreakpointLocation contains 7 attributes

6 read-only attributes:
owner: location owner's Python companion object
source: file path and line number tuple: (string, long) / None
address: installed address of the location
function: function name where location was set
fullname: fullname where location was set
thread_groups: thread groups (inferiors) where location was set.

1 writeable attribute:
enabled: get/set enable/disable this location (bool)

Access/calls to these, can all throw Python exceptions (documented in
the online documentation), and that's due to the nature
of how breakpoint locations can be invalidated
"behind the scenes", either by them being removed
from the original breakpoint or changed,
like for instance when a new symbol file is loaded, at
which point all breakpoint locations are re-created by GDB.
Therefore this patch has chosen to be non-intrusive:
it's up to the Python user to re-request the locations if
they become invalid.

Also there's event handlers that handle new object files etc, if a Python
user is storing breakpoint locations in some larger state they've
built up, refreshing the locations is easy and it only comes
with runtime overhead when the Python user wants to use them.

gdb.BreakpointLocation Python type
struct "gdbpy_breakpoint_location_object" is found in python-internal.h

Its definition, layout, methods and functions
are found in the same file as gdb.Breakpoint (py-breakpoint.c)

1 change was also made to breakpoint.h/c to make it possible
to enable and disable a bp_location* specifically,
without having its LOC_NUM, as this number
also can change arbitrarily behind the scenes.

Updated docs & news file as per request.

Testsuite: tests the .source attribute and the disabling of
individual locations.

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=18385


Change-Id: I302c1c50a557ad59d5d18c88ca19014731d736b0
2022-07-28 11:20:46 -06:00

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# Copyright (C) 2022 Free Software Foundation, Inc.
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
load_lib gdb-python.exp
standard_testfile
if {[gdb_compile "${srcdir}/${subdir}/${srcfile}" "${binfile}" executable {c++ debug}] != "" } {
return -1
}
save_vars { GDBFLAGS } {
clean_restart $testfile
}
if { [skip_python_tests] } { continue }
if ![runto_main] {
return -1
}
# Set breakpoint with 2 locations.
gdb_breakpoint "add"
set expected_line_a [gdb_get_line_number "a + b"]
set expected_line_b [gdb_get_line_number "c + d"]
# Test that the locations return correct source locations.
gdb_test "python print(gdb.breakpoints()\[1\].locations\[0\].source)" \
".*('.*py-bp-locations.c', $expected_line_a).*"
gdb_test "python print(gdb.breakpoints()\[1\].locations\[1\].source)" \
".*('.*py-bp-locations.c', $expected_line_b).*"
# Disable first location and make sure we don't hit it.
gdb_test "python gdb.breakpoints()\[1\].locations\[0\].enabled = False" ""
gdb_continue_to_breakpoint "" ".*25.*"
if ![runto_main] {
return -1
}
gdb_breakpoint "add"
# Disable "add" owner breakpoint and verify all locations still are enabled.
gdb_test "python gdb.breakpoints()\[1\].enabled = False" "" "Disable add owner breakpoint."
gdb_test "python print(gdb.breakpoints()\[1\].locations\[0\].enabled)" "True" "First location still enabled"
gdb_test "python print(gdb.breakpoints()\[1\].locations\[1\].enabled)" "True" "Second location still enabled"
# Set breakpoint at end and make sure we run past the still enabled locations,
gdb_breakpoint 32
gdb_continue_to_breakpoint "end of main" ".*32.*"