Re: [PATCH] Fix "maint selftest" regression, add struct, scoped_mock_context

Andrew Burgess
2020-06-23T16:34:57Z

* Pedro Alves <palves@redhat.com> [2020-06-23 16:38:02 +0100]:

> On 6/23/20 3:26 PM, Pedro Alves via Gdb-patches wrote:
> > On 6/23/20 2:37 PM, Andrew Burgess wrote:
>
> >> I suspect that the problem might be 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);
> >>
> >> My suspicion from a quick read of your patch above is that we need to
> >> do more than just set inferior_ptid here now.
> >
> > Indeed. Thanks for reporting it.
> >
> > I fixed this in gdbarch-selftests.c, where this code is duplicated,
> > but missed regcache.c. I'll fix it.
> >
>
> Like so. WDYT?

LGTM.

Thanks,
Andrew

>
> From d3438cc6c48bd77880da7ef7a449edbbfe990e37 Mon Sep 17 00:00:00 2001
> From: Pedro Alves <palves@redhat.com>
> Date: Tue, 23 Jun 2020 15:18:41 +0100
> Subject: [PATCH] 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:
> yyyy-mm-dd 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): Dont error out if a target is already pushed.
> Use scoped_mock_context. Adjust.
> * scoped-mock-context.h: New file.
> ---
> gdb/gdbarch-selftests.c | 39 ++--------------------
> gdb/regcache.c | 71 +++++++++-------------------------------
> gdb/scoped-mock-context.h | 82 +++++++++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 99 insertions(+), 93 deletions(-)
> create mode 100644 gdb/scoped-mock-context.h
>
> diff --git a/gdb/gdbarch-selftests.c b/gdb/gdbarch-selftests.c
> index 91aa9d87344..4f9adbd9e9c 100644
> --- a/gdb/gdbarch-selftests.c
> +++ b/gdb/gdbarch-selftests.c
> @@ -20,14 +20,12 @@
> #include "defs.h"
> #include "gdbsupport/selftest.h"
> #include "selftest-arch.h"
> -#include "inferior.h"
> -#include "gdbthread.h"
> #include "target.h"
> #include "test-target.h"
> #include "target-float.h"
> #include "gdbsupport/def-vector.h"
> #include "gdbarch.h"
> -#include "progspace-and-thread.h"
> +#include "scoped-mock-context.h"
>
> namespace selftests {
>
> @@ -71,40 +69,7 @@ register_to_value_test (struct gdbarch *gdbarch)
> builtin->builtin_char32,
> };
>
> - /* Create a mock environment. An inferior with a thread, with a
> - process_stratum target pushed. */
> -
> - test_target_ops mock_target;
> - ptid_t mock_ptid (1, 1);
> - program_space mock_pspace (new_address_space ());
> - inferior mock_inferior (mock_ptid.pid ());
> - mock_inferior.gdbarch = gdbarch;
> - mock_inferior.aspace = mock_pspace.aspace;
> - mock_inferior.pspace = &mock_pspace;
> - thread_info mock_thread (&mock_inferior, mock_ptid);
> -
> - scoped_restore_current_pspace_and_thread restore_pspace_thread;
> -
> - scoped_restore restore_thread_list
> - = make_scoped_restore (&mock_inferior.thread_list, &mock_thread);
> -
> - /* Add the mock inferior to the inferior list so that look ups by
> - target+ptid can find it. */
> - scoped_restore restore_inferior_list
> - = make_scoped_restore (&inferior_list, &mock_inferior);
> -
> - /* Switch to the mock inferior. */
> - switch_to_inferior_no_thread (&mock_inferior);
> -
> - /* Push the process_stratum target so we can mock accessing
> - registers. */
> - push_target (&mock_target);
> -
> - /* Pop it again on exit (return/exception). */
> - SCOPE_EXIT { pop_all_targets_at_and_above (process_stratum); };
> -
> - /* Switch to the mock thread. */
> - switch_to_thread (&mock_thread);
> + scoped_mock_context<test_target_ops> mockctx (gdbarch);
>
> struct frame_info *frame = get_current_frame ();
> const int num_regs = gdbarch_num_cooked_regs (gdbarch);
> diff --git a/gdb/regcache.c b/gdb/regcache.c
> index 6a4359d0f36..4ebb8cb0452 100644
> --- a/gdb/regcache.c
> +++ b/gdb/regcache.c
> @@ -22,6 +22,7 @@
> #include "gdbthread.h"
> #include "target.h"
> #include "test-target.h"
> +#include "scoped-mock-context.h"
> #include "gdbarch.h"
> #include "gdbcmd.h"
> #include "regcache.h"
> @@ -1596,49 +1597,7 @@ class readwrite_regcache : public regcache
> static void
> cooked_read_test (struct gdbarch *gdbarch)
> {
> - /* Error out if debugging something, because we're going to push the
> - test target, which would pop any existing target. */
> - if (current_top_target ()->stratum () >= process_stratum)
> - error (_("target already pushed"));
> -
> - /* Create a mock environment. An inferior with a thread, with a
> - process_stratum target pushed. */
> -
> - target_ops_no_register mock_target;
> - ptid_t mock_ptid (1, 1);
> - inferior mock_inferior (mock_ptid.pid ());
> - address_space mock_aspace {};
> - mock_inferior.gdbarch = gdbarch;
> - mock_inferior.aspace = &mock_aspace;
> - thread_info mock_thread (&mock_inferior, mock_ptid);
> - mock_inferior.thread_list = &mock_thread;
> -
> - /* Add the mock inferior to the inferior list so that look ups by
> - target+ptid can find it. */
> - scoped_restore restore_inferior_list
> - = make_scoped_restore (&inferior_list);
> - inferior_list = &mock_inferior;
> -
> - /* Switch to the mock inferior. */
> - scoped_restore_current_inferior restore_current_inferior;
> - set_current_inferior (&mock_inferior);
> -
> - /* Push the process_stratum target so we can mock accessing
> - registers. */
> - push_target (&mock_target);
> -
> - /* Pop it again on exit (return/exception). */
> - struct on_exit
> - {
> - ~on_exit ()
> - {
> - pop_all_targets_at_and_above (process_stratum);
> - }
> - } pop_targets;
> -
> - /* Switch to the mock thread. */
> - scoped_restore restore_inferior_ptid
> - = make_scoped_restore (&inferior_ptid, mock_ptid);
> + scoped_mock_context<target_ops_no_register> mockctx (gdbarch);
>
> /* Test that read one raw register from regcache_no_target will go
> to the target layer. */
> @@ -1653,21 +1612,21 @@ cooked_read_test (struct gdbarch *gdbarch)
> break;
> }
>
> - readwrite_regcache readwrite (&mock_target, gdbarch);
> + readwrite_regcache readwrite (&mockctx.mock_target, gdbarch);
> gdb::def_vector<gdb_byte> buf (register_size (gdbarch, nonzero_regnum));
>
> readwrite.raw_read (nonzero_regnum, buf.data ());
>
> /* raw_read calls target_fetch_registers. */
> - SELF_CHECK (mock_target.fetch_registers_called > 0);
> - mock_target.reset ();
> + SELF_CHECK (mockctx.mock_target.fetch_registers_called > 0);
> + mockctx.mock_target.reset ();
>
> /* Mark all raw registers valid, so the following raw registers
> accesses won't go to target. */
> for (auto i = 0; i < gdbarch_num_regs (gdbarch); i++)
> readwrite.raw_update (i);
>
> - mock_target.reset ();
> + mockctx.mock_target.reset ();
> /* Then, read all raw and pseudo registers, and don't expect calling
> to_{fetch,store}_registers. */
> for (int regnum = 0; regnum < gdbarch_num_cooked_regs (gdbarch); regnum++)
> @@ -1680,18 +1639,18 @@ cooked_read_test (struct gdbarch *gdbarch)
> SELF_CHECK (REG_VALID == readwrite.cooked_read (regnum,
> inner_buf.data ()));
>
> - SELF_CHECK (mock_target.fetch_registers_called == 0);
> - SELF_CHECK (mock_target.store_registers_called == 0);
> - SELF_CHECK (mock_target.xfer_partial_called == 0);
> + SELF_CHECK (mockctx.mock_target.fetch_registers_called == 0);
> + SELF_CHECK (mockctx.mock_target.store_registers_called == 0);
> + SELF_CHECK (mockctx.mock_target.xfer_partial_called == 0);
>
> - mock_target.reset ();
> + mockctx.mock_target.reset ();
> }
>
> readonly_detached_regcache readonly (readwrite);
>
> /* GDB may go to target layer to fetch all registers and memory for
> readonly regcache. */
> - mock_target.reset ();
> + mockctx.mock_target.reset ();
>
> for (int regnum = 0; regnum < gdbarch_num_cooked_regs (gdbarch); regnum++)
> {
> @@ -1749,11 +1708,11 @@ cooked_read_test (struct gdbarch *gdbarch)
> }
> }
>
> - SELF_CHECK (mock_target.fetch_registers_called == 0);
> - SELF_CHECK (mock_target.store_registers_called == 0);
> - SELF_CHECK (mock_target.xfer_partial_called == 0);
> + SELF_CHECK (mockctx.mock_target.fetch_registers_called == 0);
> + SELF_CHECK (mockctx.mock_target.store_registers_called == 0);
> + SELF_CHECK (mockctx.mock_target.xfer_partial_called == 0);
>
> - mock_target.reset ();
> + mockctx.mock_target.reset ();
> }
> }
>
> diff --git a/gdb/scoped-mock-context.h b/gdb/scoped-mock-context.h
> new file mode 100644
> index 00000000000..461c2a35388
> --- /dev/null
> +++ b/gdb/scoped-mock-context.h
> @@ -0,0 +1,82 @@
> +/* RAII type to create a temporary mock context.
> +
> + Copyright (C) 2020 Free Software Foundation, Inc.
> +
> + This file is part of GDB.
> +
> + 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/>. */
> +
> +#ifndef SCOPED_MOCK_CONTEXT_H
> +#define SCOPED_MOCK_CONTEXT_H
> +
> +#include "inferior.h"
> +#include "gdbthread.h"
> +#include "progspace.h"
> +#include "progspace-and-thread.h"
> +
> +#if GDB_SELF_TEST
> +namespace selftests {
> +
> +/* RAII type to create (and switch to) a temporary mock context. An
> + inferior with a thread, with a process_stratum target pushed. */
> +
> +template<typename Target>
> +struct scoped_mock_context
> +{
> + /* Order here is important. */
> +
> + Target mock_target;
> + ptid_t mock_ptid {1, 1};
> + program_space mock_pspace {new_address_space ()};
> + inferior mock_inferior {mock_ptid.pid ()};
> + thread_info mock_thread {&mock_inferior, mock_ptid};
> +
> + scoped_restore_current_pspace_and_thread restore_pspace_thread;
> +
> + scoped_restore_tmpl<thread_info *> restore_thread_list
> + {&mock_inferior.thread_list, &mock_thread};
> +
> + /* Add the mock inferior to the inferior list so that look ups by
> + target+ptid can find it. */
> + scoped_restore_tmpl<inferior *> restore_inferior_list
> + {&inferior_list, &mock_inferior};
> +
> + explicit scoped_mock_context (gdbarch *gdbarch)
> + {
> + mock_inferior.gdbarch = gdbarch;
> + mock_inferior.aspace = mock_pspace.aspace;
> + mock_inferior.pspace = &mock_pspace;
> +
> + /* Switch to the mock inferior. */
> + switch_to_inferior_no_thread (&mock_inferior);
> +
> + /* Push the process_stratum target so we can mock accessing
> + registers. */
> + gdb_assert (mock_target.stratum () == process_stratum);
> + push_target (&mock_target);
> +
> + /* Switch to the mock thread. */
> + switch_to_thread (&mock_thread);
> + }
> +
> + ~scoped_mock_context ()
> + {
> + pop_all_targets_at_and_above (process_stratum);
> + }
> +};
> +
> +} // namespace selftests
> +#endif /* GDB_SELF_TEST */
> +
> +#endif /* !defined (SCOPED_MOCK_CONTEXT_H) */
>
> base-commit: 39ff0b812324f4b050bb0b367b269db6d4d0cb8b
> --
> 2.14.5
>