Fix "maint selftest" regression, add struct scoped_mock_context
This commit:
commit 3922b302645fda04da42a5279399578ae2f6206c
Author: Pedro Alves <palves@redhat.com>
AuthorDate: Thu Jun 18 21:28:37 2020 +0100
Decouple inferior_ptid/inferior_thread(); dup ptids in thread list (PR 25412)
caused a regression for gdb.gdb/unittest.exp when GDB is configured
with --enable-targets=all. The failure is:
gdb/thread.c:95: internal-error: thread_info* inferior_thread(): Assertion `current_thread_ != nullptr' failed.
The problem is in this line in regcache.c:cooked_read_test:
/* Switch to the mock thread. */
scoped_restore restore_inferior_ptid
= make_scoped_restore (&inferior_ptid, mock_ptid);
Both gdbarch-selftest.c and regcache.c set up a similar mock context,
but the series the patch above belongs to only updated the
gdbarch-selftest.c context to not write to inferior_ptid directly, and
missed updating regcache.c's.
Instead of copying the fix over to regcache.c, share the mock context
setup code in a new RAII class, based on gdbarch-selftest.c's version.
Also remove the "target already pushed" error from regcache.c, like it
had been removed from gdbarch-selftest.c in the multi-target series.
That check is unnecessary because each inferior now has its own target
stack, and the unit test pushes a target on a separate (mock)
inferior, not the current inferior on entry.
gdb/ChangeLog:
2020-06-23 Pedro Alves <palves@redhat.com>
* gdbarch-selftests.c: Don't include inferior.h, gdbthread.h or
progspace-and-thread.h. Include scoped-mock-context.h instead.
(register_to_value_test): Use scoped_mock_context.
* regcache.c: Include "scoped-mock-context.h".
(cooked_read_test): Don't error out if a target is already pushed.
Use scoped_mock_context. Adjust.
* scoped-mock-context.h: New file.
2020-06-23 22:18:41 +08:00
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/* RAII type to create a temporary mock context.
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2022-01-01 22:56:03 +08:00
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Copyright (C) 2020-2022 Free Software Foundation, Inc.
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Fix "maint selftest" regression, add struct scoped_mock_context
This commit:
commit 3922b302645fda04da42a5279399578ae2f6206c
Author: Pedro Alves <palves@redhat.com>
AuthorDate: Thu Jun 18 21:28:37 2020 +0100
Decouple inferior_ptid/inferior_thread(); dup ptids in thread list (PR 25412)
caused a regression for gdb.gdb/unittest.exp when GDB is configured
with --enable-targets=all. The failure is:
gdb/thread.c:95: internal-error: thread_info* inferior_thread(): Assertion `current_thread_ != nullptr' failed.
The problem is in this line in regcache.c:cooked_read_test:
/* Switch to the mock thread. */
scoped_restore restore_inferior_ptid
= make_scoped_restore (&inferior_ptid, mock_ptid);
Both gdbarch-selftest.c and regcache.c set up a similar mock context,
but the series the patch above belongs to only updated the
gdbarch-selftest.c context to not write to inferior_ptid directly, and
missed updating regcache.c's.
Instead of copying the fix over to regcache.c, share the mock context
setup code in a new RAII class, based on gdbarch-selftest.c's version.
Also remove the "target already pushed" error from regcache.c, like it
had been removed from gdbarch-selftest.c in the multi-target series.
That check is unnecessary because each inferior now has its own target
stack, and the unit test pushes a target on a separate (mock)
inferior, not the current inferior on entry.
gdb/ChangeLog:
2020-06-23 Pedro Alves <palves@redhat.com>
* gdbarch-selftests.c: Don't include inferior.h, gdbthread.h or
progspace-and-thread.h. Include scoped-mock-context.h instead.
(register_to_value_test): Use scoped_mock_context.
* regcache.c: Include "scoped-mock-context.h".
(cooked_read_test): Don't error out if a target is already pushed.
Use scoped_mock_context. Adjust.
* scoped-mock-context.h: New file.
2020-06-23 22:18:41 +08:00
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This file is part of GDB.
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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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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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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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#ifndef SCOPED_MOCK_CONTEXT_H
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#define SCOPED_MOCK_CONTEXT_H
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#include "inferior.h"
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#include "gdbthread.h"
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#include "progspace.h"
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#include "progspace-and-thread.h"
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#if GDB_SELF_TEST
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namespace selftests {
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/* RAII type to create (and switch to) a temporary mock context. An
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inferior with a thread, with a process_stratum target pushed. */
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template<typename Target>
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struct scoped_mock_context
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{
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/* Order here is important. */
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Target mock_target;
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ptid_t mock_ptid {1, 1};
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program_space mock_pspace {new_address_space ()};
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inferior mock_inferior {mock_ptid.pid ()};
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thread_info mock_thread {&mock_inferior, mock_ptid};
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scoped_restore_current_pspace_and_thread restore_pspace_thread;
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explicit scoped_mock_context (gdbarch *gdbarch)
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{
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2020-06-15 03:57:04 +08:00
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/* Add the mock inferior to the inferior list so that look ups by
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target+ptid can find it. */
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inferior_list.push_back (mock_inferior);
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gdb: introduce intrusive_list, make thread_info use it
GDB currently has several objects that are put in a singly linked list,
by having the object's type have a "next" pointer directly. For
example, struct thread_info and struct inferior. Because these are
simply-linked lists, and we don't keep track of a "tail" pointer, when
we want to append a new element on the list, we need to walk the whole
list to find the current tail. It would be nice to get rid of that
walk. Removing elements from such lists also requires a walk, to find
the "previous" position relative to the element being removed. To
eliminate the need for that walk, we could make those lists
doubly-linked, by adding a "prev" pointer alongside "next". It would be
nice to avoid the boilerplate associated with maintaining such a list
manually, though. That is what the new intrusive_list type addresses.
With an intrusive list, it's also possible to move items out of the
list without destroying them, which is interesting in our case for
example for threads, when we exit them, but can't destroy them
immediately. We currently keep exited threads on the thread list, but
we could change that which would simplify some things.
Note that with std::list, element removal is O(N). I.e., with
std::list, we need to walk the list to find the iterator pointing to
the position to remove. However, we could store a list iterator
inside the object as soon as we put the object in the list, to address
it, because std::list iterators are not invalidated when other
elements are added/removed. However, if you need to put the same
object in more than one list, then std::list<object> doesn't work.
You need to instead use std::list<object *>, which is less efficient
for requiring extra memory allocations. For an example of an object
in multiple lists, see the step_over_next/step_over_prev fields in
thread_info:
/* Step-over chain. A thread is in the step-over queue if these are
non-NULL. If only a single thread is in the chain, then these
fields point to self. */
struct thread_info *step_over_prev = NULL;
struct thread_info *step_over_next = NULL;
The new intrusive_list type gives us the advantages of an intrusive
linked list, while avoiding the boilerplate associated with manually
maintaining it.
intrusive_list's API follows the standard container interface, and thus
std::list's interface. It is based the API of Boost's intrusive list,
here:
https://www.boost.org/doc/libs/1_73_0/doc/html/boost/intrusive/list.html
Our implementation is relatively simple, while Boost's is complicated
and intertwined due to a lot of customization options, which our version
doesn't have.
The easiest way to use an intrusive_list is to make the list's element
type inherit from intrusive_node. This adds a prev/next pointers to
the element type. However, to support putting the same object in more
than one list, intrusive_list supports putting the "node" info as a
field member, so you can have more than one such nodes, one per list.
As a first guinea pig, this patch makes the per-inferior thread list use
intrusive_list using the base class method.
Unlike Boost's implementation, ours is not a circular list. An earlier
version of the patch was circular: the intrusive_list type included an
intrusive_list_node "head". In this design, a node contained pointers
to the previous and next nodes, not the previous and next elements.
This wasn't great for when debugging GDB with GDB, as it was difficult
to get from a pointer to the node to a pointer to the element. With the
design proposed in this patch, nodes contain pointers to the previous
and next elements, making it easy to traverse the list by hand and
inspect each element.
The intrusive_list object contains pointers to the first and last
elements of the list. They are nullptr if the list is empty.
Each element's node contains a pointer to the previous and next
elements. The first element's previous pointer is nullptr and the last
element's next pointer is nullptr. Therefore, if there's a single
element in the list, both its previous and next pointers are nullptr.
To differentiate such an element from an element that is not linked into
a list, the previous and next pointers contain a special value (-1) when
the node is not linked. This is necessary to be able to reliably tell
if a given node is currently linked or not.
A begin() iterator points to the first item in the list. An end()
iterator contains nullptr. This makes iteration until end naturally
work, as advancing past the last element will make the iterator contain
nullptr, making it equal to the end iterator. If the list is empty,
a begin() iterator will contain nullptr from the start, and therefore be
immediately equal to the end.
Iterating on an intrusive_list yields references to objects (e.g.
`thread_info&`). The rest of GDB currently expects iterators and ranges
to yield pointers (e.g. `thread_info*`). To bridge the gap, add the
reference_to_pointer_iterator type. It is used to define
inf_threads_iterator.
Add a Python pretty-printer, to help inspecting intrusive lists when
debugging GDB with GDB. Here's an example of the output:
(top-gdb) p current_inferior_.m_obj.thread_list
$1 = intrusive list of thread_info = {0x61700002c000, 0x617000069080, 0x617000069400, 0x61700006d680, 0x61700006eb80}
It's not possible with current master, but with this patch [1] that I
hope will be merged eventually, it's possible to index the list and
access the pretty-printed value's children:
(top-gdb) p current_inferior_.m_obj.thread_list[1]
$2 = (thread_info *) 0x617000069080
(top-gdb) p current_inferior_.m_obj.thread_list[1].ptid
$3 = {
m_pid = 406499,
m_lwp = 406503,
m_tid = 0
}
Even though iterating the list in C++ yields references, the Python
pretty-printer yields pointers. The reason for this is that the output
of printing the thread list above would be unreadable, IMO, if each
thread_info object was printed in-line, since they contain so much
information. I think it's more useful to print pointers, and let the
user drill down as needed.
[1] https://sourceware.org/pipermail/gdb-patches/2021-April/178050.html
Co-Authored-By: Simon Marchi <simon.marchi@efficios.com>
Change-Id: I3412a14dc77f25876d742dab8f44e0ba7c7586c0
2021-06-12 06:28:32 +08:00
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mock_inferior.thread_list.push_back (mock_thread);
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2021-06-12 06:29:33 +08:00
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mock_inferior.ptid_thread_map[mock_ptid] = &mock_thread;
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Fix "maint selftest" regression, add struct scoped_mock_context
This commit:
commit 3922b302645fda04da42a5279399578ae2f6206c
Author: Pedro Alves <palves@redhat.com>
AuthorDate: Thu Jun 18 21:28:37 2020 +0100
Decouple inferior_ptid/inferior_thread(); dup ptids in thread list (PR 25412)
caused a regression for gdb.gdb/unittest.exp when GDB is configured
with --enable-targets=all. The failure is:
gdb/thread.c:95: internal-error: thread_info* inferior_thread(): Assertion `current_thread_ != nullptr' failed.
The problem is in this line in regcache.c:cooked_read_test:
/* Switch to the mock thread. */
scoped_restore restore_inferior_ptid
= make_scoped_restore (&inferior_ptid, mock_ptid);
Both gdbarch-selftest.c and regcache.c set up a similar mock context,
but the series the patch above belongs to only updated the
gdbarch-selftest.c context to not write to inferior_ptid directly, and
missed updating regcache.c's.
Instead of copying the fix over to regcache.c, share the mock context
setup code in a new RAII class, based on gdbarch-selftest.c's version.
Also remove the "target already pushed" error from regcache.c, like it
had been removed from gdbarch-selftest.c in the multi-target series.
That check is unnecessary because each inferior now has its own target
stack, and the unit test pushes a target on a separate (mock)
inferior, not the current inferior on entry.
gdb/ChangeLog:
2020-06-23 Pedro Alves <palves@redhat.com>
* gdbarch-selftests.c: Don't include inferior.h, gdbthread.h or
progspace-and-thread.h. Include scoped-mock-context.h instead.
(register_to_value_test): Use scoped_mock_context.
* regcache.c: Include "scoped-mock-context.h".
(cooked_read_test): Don't error out if a target is already pushed.
Use scoped_mock_context. Adjust.
* scoped-mock-context.h: New file.
2020-06-23 22:18:41 +08:00
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mock_inferior.gdbarch = gdbarch;
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mock_inferior.aspace = mock_pspace.aspace;
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mock_inferior.pspace = &mock_pspace;
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/* Switch to the mock inferior. */
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switch_to_inferior_no_thread (&mock_inferior);
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/* Push the process_stratum target so we can mock accessing
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registers. */
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gdb_assert (mock_target.stratum () == process_stratum);
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2021-03-23 21:50:35 +08:00
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mock_inferior.push_target (&mock_target);
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Fix "maint selftest" regression, add struct scoped_mock_context
This commit:
commit 3922b302645fda04da42a5279399578ae2f6206c
Author: Pedro Alves <palves@redhat.com>
AuthorDate: Thu Jun 18 21:28:37 2020 +0100
Decouple inferior_ptid/inferior_thread(); dup ptids in thread list (PR 25412)
caused a regression for gdb.gdb/unittest.exp when GDB is configured
with --enable-targets=all. The failure is:
gdb/thread.c:95: internal-error: thread_info* inferior_thread(): Assertion `current_thread_ != nullptr' failed.
The problem is in this line in regcache.c:cooked_read_test:
/* Switch to the mock thread. */
scoped_restore restore_inferior_ptid
= make_scoped_restore (&inferior_ptid, mock_ptid);
Both gdbarch-selftest.c and regcache.c set up a similar mock context,
but the series the patch above belongs to only updated the
gdbarch-selftest.c context to not write to inferior_ptid directly, and
missed updating regcache.c's.
Instead of copying the fix over to regcache.c, share the mock context
setup code in a new RAII class, based on gdbarch-selftest.c's version.
Also remove the "target already pushed" error from regcache.c, like it
had been removed from gdbarch-selftest.c in the multi-target series.
That check is unnecessary because each inferior now has its own target
stack, and the unit test pushes a target on a separate (mock)
inferior, not the current inferior on entry.
gdb/ChangeLog:
2020-06-23 Pedro Alves <palves@redhat.com>
* gdbarch-selftests.c: Don't include inferior.h, gdbthread.h or
progspace-and-thread.h. Include scoped-mock-context.h instead.
(register_to_value_test): Use scoped_mock_context.
* regcache.c: Include "scoped-mock-context.h".
(cooked_read_test): Don't error out if a target is already pushed.
Use scoped_mock_context. Adjust.
* scoped-mock-context.h: New file.
2020-06-23 22:18:41 +08:00
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/* Switch to the mock thread. */
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switch_to_thread (&mock_thread);
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}
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~scoped_mock_context ()
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{
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2020-06-15 03:57:04 +08:00
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inferior_list.erase (inferior_list.iterator_to (mock_inferior));
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Fix "maint selftest" regression, add struct scoped_mock_context
This commit:
commit 3922b302645fda04da42a5279399578ae2f6206c
Author: Pedro Alves <palves@redhat.com>
AuthorDate: Thu Jun 18 21:28:37 2020 +0100
Decouple inferior_ptid/inferior_thread(); dup ptids in thread list (PR 25412)
caused a regression for gdb.gdb/unittest.exp when GDB is configured
with --enable-targets=all. The failure is:
gdb/thread.c:95: internal-error: thread_info* inferior_thread(): Assertion `current_thread_ != nullptr' failed.
The problem is in this line in regcache.c:cooked_read_test:
/* Switch to the mock thread. */
scoped_restore restore_inferior_ptid
= make_scoped_restore (&inferior_ptid, mock_ptid);
Both gdbarch-selftest.c and regcache.c set up a similar mock context,
but the series the patch above belongs to only updated the
gdbarch-selftest.c context to not write to inferior_ptid directly, and
missed updating regcache.c's.
Instead of copying the fix over to regcache.c, share the mock context
setup code in a new RAII class, based on gdbarch-selftest.c's version.
Also remove the "target already pushed" error from regcache.c, like it
had been removed from gdbarch-selftest.c in the multi-target series.
That check is unnecessary because each inferior now has its own target
stack, and the unit test pushes a target on a separate (mock)
inferior, not the current inferior on entry.
gdb/ChangeLog:
2020-06-23 Pedro Alves <palves@redhat.com>
* gdbarch-selftests.c: Don't include inferior.h, gdbthread.h or
progspace-and-thread.h. Include scoped-mock-context.h instead.
(register_to_value_test): Use scoped_mock_context.
* regcache.c: Include "scoped-mock-context.h".
(cooked_read_test): Don't error out if a target is already pushed.
Use scoped_mock_context. Adjust.
* scoped-mock-context.h: New file.
2020-06-23 22:18:41 +08:00
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pop_all_targets_at_and_above (process_stratum);
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}
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};
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} // namespace selftests
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#endif /* GDB_SELF_TEST */
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#endif /* !defined (SCOPED_MOCK_CONTEXT_H) */
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