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6383eda55a
Remove the frame_object::frame_id_is_next field. This has been part
of how Python handles frames since this code was first added in commit
f8f6f20b6e back in 2009. The motivation
for this field can be found in a couple of comments, there's this one
on frame_id_is_next:
/* Marks that the FRAME_ID member actually holds the ID of the frame next
to this, and not this frames' ID itself. This is a hack to permit Python
frame objects which represent invalid frames (i.e., the last frame_info
in a corrupt stack). The problem arises from the fact that this code
relies on FRAME_ID to uniquely identify a frame, which is not always true
for the last "frame" in a corrupt stack (it can have a null ID, or the same
ID as the previous frame). Whenever get_prev_frame returns NULL, we
record the frame_id of the next frame and set FRAME_ID_IS_NEXT to 1. */
And this one in frame_info_to_frame_object:
/* Try to get the previous frame, to determine if this is the last frame
in a corrupt stack. If so, we need to store the frame_id of the next
frame and not of this one (which is possibly invalid). */
This field is dealing with a problem that was present in older
versions of GDB where not every stack frame had a valid frame-id, if
the stack was corrupted in some way then the last frame might have an
invalid frame-id. However, that is no longer the case. With current
GDB there is a promise that every frame has a valid frame-id. I don't
have a single commit to point to where this became the reality, but it
is my understanding of current GDB.
As an example, the frame-id of every frame (except #0) is computed as
the frame is created, any frames with a duplicate frame-id, or any
errors during computation of the frame-id, and the new frame is
discarded.
Additionally, our frame_info_ptr::reinflate mechanism relies on unique
and valid frame-ids.
The problem with the existing code is that the last frame in a
corrupted stack will hold the frame-id of the next frame, that is, the
more inner frame. This means we have two frames holding the same
frame-id, and the only difference is the frame_id_is_next flag.
However, the frapy_str function, which prints a string representation
of the frame, doesn't take frame_id_is_next into account, so printing
the last two frames in a corrupted stack, will print the same
frame-id.
We could fix this in frapy_str and also frapy_repr by checking the
frame_id_is_next flag and then fetching the previous frame-id, but
this would still assume that the previous frame has a valid-id, so we
might as well just drop the frame_id_is_next flag and make everything
simpler.
There's a new test which exposes the incorrectly printed frame-id
problem.
While testing I needed to "fix" the results for two existing tests.
In frame_info_to_frame_object, in order to figure out if we should use
the next frame, we called get_prev_frame. This would cause GDB to
always unwind 1 extra level of the stack.
What this means is that, if there is an error, or some diagnostic
output, when unwinding frame #1, then this will show up when trying to
access frame #0 via the Python API as frame_info_to_frame_object on
frame #0 would call get_prev_frame, which would then unwind frame #1.
After this commit this is no longer the case. We only see
output (either errors, or diagnostic output) associated with frame #1
when we actually try to unwind to frame #1. The two tests that needed
updating were expecting output associated with frame #1 while printing
frame #0. This is now fixed and the output for frame #1 occurs later
on. I think this is an improvement.
250 lines
10 KiB
Text
250 lines
10 KiB
Text
# Copyright (C) 2009-2026 Free Software Foundation, Inc.
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# This program is free software; you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation; either version 3 of the License, or
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# (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with this program. If not, see <http://www.gnu.org/licenses/>.
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# This file is part of the GDB testsuite. It tests the mechanism
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# exposing values to Python.
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load_lib gdb-python.exp
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require allow_python_tests
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standard_testfile
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if { [prepare_for_testing "failed to prepare" ${testfile} ${srcfile}] } {
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return
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}
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# The following tests require execution.
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if {![runto_main]} {
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return
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}
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gdb_breakpoint [gdb_get_line_number "Block break here."]
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gdb_continue_to_breakpoint "Block break here."
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gdb_py_test_silent_cmd "python bf1 = gdb.selected_frame ()" "get frame" 0
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# Test Frame.__repr__() method for a valid Frame object.
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gdb_test "python print (repr(bf1))" "<gdb\\.Frame level=0 frame-id=\\{\[^\r\n\]+\\}>" \
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"test __repr__ for gdb.Frame on a valid frame"
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# Test Frame.architecture() method.
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gdb_py_test_silent_cmd "python show_arch_str = gdb.execute(\"show architecture\", to_string=True)" "show arch" 0
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gdb_test "python print (bf1.architecture().name() in show_arch_str)" "True" "test Frame.architecture()"
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# First test that read_var is unaffected by PR 11036 changes.
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gdb_test "python print (bf1.read_var(\"i\"))" "\"stuff\"" "test i"
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gdb_test "python print (bf1.read_var(\"f\"))" "\"foo\"" "test f"
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gdb_test "python print (bf1.read_var(\"b\"))" "\"bar\"" "test b"
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# Check we can use a single named argument with read_var.
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gdb_test "python print (bf1.read_var(variable = \"b\"))" "\"bar\"" \
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"test b using named arguments"
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# Test the read_var function in another block other than the current
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# block (in this case, the super block). Test that read_var is reading
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# the correct variables of i and f but they are the correct value and type.
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gdb_py_test_silent_cmd "python sb = bf1.block().superblock" "get superblock" 0
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gdb_test "python print (bf1.read_var(\"i\", sb))" "1.1.*" "test i = 1.1"
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gdb_test "python print (bf1.read_var(\"i\", sb).type)" "double" "test double i"
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gdb_test "python print (bf1.read_var(\"f\", sb))" "2.2.*" "test f = 2.2"
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gdb_test "python print (bf1.read_var(\"f\", sb).type)" "double" "test double f"
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# Now test read_var with a variable and block using named arguments.
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gdb_test "python print (bf1.read_var(block = sb, variable = \"i\"))" "1.1.*" \
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"test i = 1.1 using named arguments"
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gdb_test "python print (bf1.read_var(block = sb, variable = \"f\"))" "2.2.*" \
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"test f = 2.2 using named arguments"
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# And again test another outerblock, this time testing "i" is the
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# correct value and type.
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gdb_py_test_silent_cmd "python sb = sb.superblock" "get superblock" 0
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gdb_test "python print (bf1.read_var(\"i\", sb))" "99" "test i = 99"
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gdb_test "python print (bf1.read_var(\"i\", sb).type)" "int" "test int i"
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# Test what happens when we provide a block of the wrong type.
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gdb_test "python print (bf1.read_var(\"i\", \"some_block\"))" \
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[multi_line \
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"TypeError.*: argument 2 must be gdb\\.Block, not str" \
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"Error occurred in Python.*"] \
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"check invalid block type error"
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gdb_test "python print (bf1.read_var(block = \"some_block\", variable = \"i\"))" \
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[multi_line \
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"TypeError.*: argument 2 must be gdb\\.Block, not str" \
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"Error occurred in Python.*"] \
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"check invalid block type error when named args are used"
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# Test what happens when we provide a variable of the wrong type.
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gdb_test "python print (bf1.read_var(None))" \
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[multi_line \
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"TypeError.*: argument 1 must be gdb\\.Symbol or str, not NoneType" \
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"Error occurred in Python.*"] \
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"check read_var error when variable is None"
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gdb_test "python print (bf1.read_var(sb))" \
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[multi_line \
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"TypeError.*: argument 1 must be gdb\\.Symbol or str, not gdb\\.Block" \
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"Error occurred in Python.*"] \
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"check read_var error when variable is a gdb.Block"
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gdb_breakpoint "f2"
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gdb_continue_to_breakpoint "breakpoint at f2"
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gdb_py_test_silent_cmd "python bframe = gdb.selected_frame()" \
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"get bottommost frame" 0
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gdb_test "up" ".*" ""
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# Test Frame.__repr__() method for an invalid Frame object.
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gdb_test "python print (repr(bf1))" "<gdb\\.Frame \\(invalid\\)>" \
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"test __repr__ for gdb.Frame on an invalid frame"
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gdb_py_test_silent_cmd "python f1 = gdb.selected_frame ()" "get second frame" 0
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gdb_py_test_silent_cmd "python f0 = f1.newer ()" "get first frame" 0
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gdb_py_test_silent_cmd "python f2 = f1.older ()" "get last frame" 0
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# Check the Frame.level method.
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gdb_test "python print ('bframe.level = %d' % bframe.level ())" \
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"bframe\\.level = 0"
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gdb_test "python print ('f0.level = %d' % f0.level ())" \
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"f0\\.level = 0"
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gdb_test "python print ('f1.level = %d' % f1.level ())" \
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"f1\\.level = 1"
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gdb_test "python print ('f2.level = %d' % f2.level ())" \
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"f2\\.level = 2"
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gdb_test "python print (f1 == gdb.newest_frame())" False \
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"selected frame -vs- newest frame"
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gdb_test "python print (bframe == gdb.newest_frame())" True \
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"newest frame -vs- newest frame"
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gdb_test "python print ('result = %s' % (f0 == f1))" " = False" "test equality comparison, false"
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gdb_test "python print ('result = %s' % (f0 == f0))" " = True" "test equality comparison, true"
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gdb_test "python print ('result = %s' % (f0 != f1))" " = True" "test inequality comparison, true"
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gdb_test "python print ('result = %s' % (f0 != f0))" " = False" "test inequality comparison, false"
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gdb_test "python print ('result = %s' % f0.is_valid ())" " = True" "test Frame.is_valid"
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gdb_test "python print ('result = %s' % f0.name ())" " = f2" "test Frame.name"
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gdb_test "python print ('result = %s' % (f0.type () == gdb.NORMAL_FRAME))" " = True" "test Frame.type"
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gdb_test "python print ('result = %s' % (f0.unwind_stop_reason () == gdb.FRAME_UNWIND_NO_REASON))" \
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" = True" "test Frame.unwind_stop_reason"
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gdb_test "python print ('result = %s' % gdb.frame_stop_reason_string (gdb.FRAME_UNWIND_INNER_ID))" " = previous frame inner to this frame \\(corrupt stack\\?\\)" "test gdb.frame_stop_reason_string"
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gdb_test "python print ('result = %s' % f0.pc ())" " = ${::decimal}" "test Frame.pc"
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gdb_test "python print ('result = %s' % (f0.older () == f1))" " = True" "test Frame.older"
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gdb_test "python print ('result = %s' % (f1.newer () == f0))" " = True" "test Frame.newer"
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gdb_test "python print ('result = %s' % f0.read_var ('variable_which_surely_doesnt_exist'))" \
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"ValueError.*: Variable 'variable_which_surely_doesnt_exist' not found.*Error occurred in Python.*" \
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"test Frame.read_var - error"
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gdb_test "python print ('result = %s' % f0.read_var ('a'))" " = 1" "test Frame.read_var - success"
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gdb_test "python print ('result = %s' % (gdb.selected_frame () == f1))" " = True" "test gdb.selected_frame"
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# Can read SP register.
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gdb_test "python print ('result = %s' % (gdb.selected_frame ().read_register ('sp') == gdb.parse_and_eval ('\$sp')))" \
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" = True" \
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"test Frame.read_register(sp)"
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# PC value obtained via read_register is as expected.
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gdb_test "python print ('result = %s' % (f0.read_register('pc') == f0.pc()))" \
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" = True" \
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"test Frame.read_register(pc)"
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# Repeat the previous test, but this time use named arguments for the
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# read_register method call.
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gdb_test "python print ('result = %s' % (f0.read_register(register = 'pc') == f0.pc()))" \
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" = True" \
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"test Frame.read_register() using named arguments"
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# Test arch-specific register name.
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set pc ""
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if {[is_amd64_regs_target]} {
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set pc "rip"
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} elseif {[is_x86_like_target]} {
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set pc "eip"
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}
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if { $pc != "" } {
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gdb_test "python print ('result = %s' % (f0.read_register('pc') == f0.read_register('$pc')))" \
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" = True" \
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"test Frame.read_register($pc)"
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}
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# Test language.
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gdb_test "python print(gdb.selected_frame().language())" "c"
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gdb_test "set language ada"
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gdb_test "python print(gdb.selected_frame().language())" "c" \
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"frame language is not affected by global language"
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# This previously caused a crash -- the implementation was missing the
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# case where a register had an unexpected type.
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gdb_test "python print(gdb.selected_frame().read_register(list()))" \
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".*Invalid type for register.*" \
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"test Frame.read_register with list"
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gdb_test_multiline "setup a bad object" \
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"python" "" \
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"class bad_type:" "" \
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" def __init__ (self):" "" \
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" pass" "" \
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" @property" "" \
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" def __class__(self):" "" \
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" raise RuntimeError('error from __class in bad_type')" "" \
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"bad_object = bad_type()" "" \
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"end" ""
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gdb_test "python print(gdb.selected_frame().read_register(bad_object))" \
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".*Invalid type for register.*" \
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"test Frame.read_register with bad_type object"
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# Load the Python script, this includes a frame unwinder which can be
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# used to "corrupt" the backtrace by introducing a cycle.
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set remote_python_file [gdb_remote_download host ${srcdir}/${subdir}/${testfile}.py]
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gdb_test_no_output "source ${remote_python_file}" "load python file"
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# Check that the frame-id as read by Python is correct for each frame
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# in the backtrace. When STOP_AT_LEVEL is None then the stack is not
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# corrupted. For other STOP_AT_LEVEL values a cycle is introduced
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# into the stack after the numbered level. E.g. for STOP_AT_LEVEL 0,
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# frame #1 will appear to have the same frame-id as #0, which
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# terminates the unwind.
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foreach_with_prefix stop_at_level { None 0 1 2 } {
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gdb_test_no_output "python global_unwinder.stop_at_level = $stop_at_level"
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if { $stop_at_level eq "None" } {
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set frame_limit 3
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} else {
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set frame_limit [expr {$stop_at_level + 1}]
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}
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for { set i 0 } { $i < $frame_limit } { incr i } {
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gdb_test "frame $i" ".*" "select frame $i"
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set expected_output [capture_command_output "maint print frame-id" \
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[string_to_regexp "frame-id for frame #$i: "]]
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set python_output [capture_command_output \
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"python print(gdb.selected_frame())" ""]
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gdb_assert { $python_output eq $expected_output } \
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"frame-id for frame $i"
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}
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}
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# Compile again without debug info.
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if { [prepare_for_testing "failed to prepare" ${testfile}-nodebug ${srcfile} {}] } {
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return
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}
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if {![runto_main]} {
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return
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}
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# Test if Frame.static_link works for a frame without debug info.
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gdb_test "python print(gdb.selected_frame().static_link())" "None" \
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"test Frame.static_link for a frame without debug info"
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