[PATCH v5 4/5] gdb: introduce ability to disable frame unwinders

Guinevere Larsen
2024-10-01T18:44:27Z

From: Guinevere Larsen <blarsen@redhat.com>

Sometimes, in the GDB testsuite, we want to test the ability of specific
unwinders to handle some piece of code. Usually this is done by trying
to outsmart GDB, or by coercing the compiler to remove information that
GDB would rely on. Both approaches have problems as GDB gets smarter
with time, and that compilers might differ in version and behavior, or
simply introduce new useful information. This was requested back in 2003
in PR backtrace/8434.

To improve our ability to thoroughly test GDB, this patch introduces a
new maintenance command that allows a user to disable some unwinders,
based on either the name of the unwinder or on its class. With this
change, it will now be possible for GDB to not find any frame unwinders
for a given frame, which would previously cause GDB to assert. GDB will
now check if any frame unwinder has been disabled, and if some has, it
will just error out instead of asserting.

Unwinders can be disabled or re-enabled in 3 different ways:
* Disabling/enabling all at once (using '-all').
* By specifying an unwinder class to be disabled (option '-class').
* By specifying the name of an unwinder (option '-name').

If you give no options to the command, GDB assumes the input is an
unwinder class. '-class' would make no difference if used, is just here
for completeness.

This command is meant to be used once the inferior is already at the
desired location for the test. An example session would be:

(gdb) start
Temporary breakpoint 1, main () at omp.c:17
17 func();
(gdb) maint frame-unwinder disable ARCH
(gdb) bt
\#0 main () at omp.c:17
(gdb) maint frame-unwinder enable ARCH
(gdb) cont
Continuing.

This commit is a more generic version of commit 3c3bb0580be0,
and so, based on the final paragraph of the commit message:
gdb: Add switch to disable DWARF stack unwinders
<...>
If in the future we find ourselves adding more switches to disable
different unwinders, then we should probably move to a more generic
solution, and remove this patch.
This patch also reverts 3c3bb0580be0

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=8434
---
gdb/NEWS | 17 ++
gdb/doc/gdb.texinfo | 49 +++---
gdb/dwarf2/frame-tailcall.c | 3 -
gdb/dwarf2/frame.c | 30 ----
gdb/dwarf2/frame.h | 6 -
gdb/frame-unwind.c | 163 +++++++++++++++++-
gdb/frame-unwind.h | 13 ++
.../gdb.base/frame-info-consistent.exp | 6 +-
gdb/testsuite/gdb.base/frame-unwind-disable.c | 21 +++
.../gdb.base/frame-unwind-disable.exp | 140 +++++++++++++++
gdb/testsuite/gdb.base/maint.exp | 4 -
11 files changed, 377 insertions(+), 75 deletions(-)
create mode 100644 gdb/testsuite/gdb.base/frame-unwind-disable.c
create mode 100644 gdb/testsuite/gdb.base/frame-unwind-disable.exp

diff --git a/gdb/NEWS b/gdb/NEWS
index 6c5def83529..1649e1d65fc 100644
--- a/gdb/NEWS
+++ b/gdb/NEWS
@@ -81,6 +81,13 @@ maintenance info blocks [ADDRESS]
are listed starting at the inner global block out to the most inner
block.

+maintenance frame-unwinder disable [-all | -name NAME | [-class] CLASS]
+maintenance frame-unwinder enable [-all | -name NAME | [-class] CLASS]
+ Enable or disable frame unwinders. This is only meant to be used when
+ testing unwinders themselves, and you want to ensure that a fallback
+ algorithm won't obscure a regression. GDB is not expected to behave
+ well if you try to execute the inferior with unwinders disabled.
+
* Changed commands

remove-symbol-file
@@ -110,6 +117,16 @@ maintenance print remote-registers
mainenance info frame-unwinders
Add a CLASS column to the output. This class is a somewhat arbitrary
grouping of unwinders, based on which area of GDB adds the unwinder.
+ Also add an ENABLED column, that will show if the unwinder is enabled
+ or not.
+
+maintenance set dwarf unwinders (on|off)
+ This command has been removed because the same functionality can be
+ achieved with maint frame-unwinder (enable|disable) DEBUGINFO.
+
+maintenance show dwarf unwinders
+ This command has been removed since the functionality can be achieved
+ by checking the last column of maint info frame-unwinders.

* New remote packets

diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index faca1e988fd..1efdf9c7b79 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -42180,31 +42180,6 @@ On hosts without threading, or where worker threads have been disabled
at runtime, this setting has no effect, as DWARF reading is always
done on the main thread, and is therefore always synchronous.

-@kindex maint set dwarf unwinders
-@kindex maint show dwarf unwinders
-@item maint set dwarf unwinders
-@itemx maint show dwarf unwinders
-Control use of the DWARF frame unwinders.
-
-@cindex DWARF frame unwinders
-Many targets that support DWARF debugging use @value{GDBN}'s DWARF
-frame unwinders to build the backtrace. Many of these targets will
-also have a second mechanism for building the backtrace for use in
-cases where DWARF information is not available, this second mechanism
-is often an analysis of a function's prologue.
-
-In order to extend testing coverage of the second level stack
-unwinding mechanisms it is helpful to be able to disable the DWARF
-stack unwinders, this can be done with this switch.
-
-In normal use of @value{GDBN} disabling the DWARF unwinders is not
-advisable, there are cases that are better handled through DWARF than
-prologue analysis, and the debug experience is likely to be better
-with the DWARF frame unwinders enabled.
-
-If DWARF frame unwinders are not supported for a particular target
-architecture, then enabling this flag does not cause them to be used.
-
@kindex maint info frame-unwinders
@item maint info frame-unwinders
List the frame unwinders currently in effect, starting with the highest
@@ -42222,6 +42197,30 @@ Unwinders installed by debug information readers.
Unwinders installed by the architecture specific code.
@end table

+@kindex maint frame-unwinder disable
+@kindex maint frame-unwinder enable
+@item maint frame-unwinder disable [@code{-all} | @code{-name} @var{name} | [@code{-class}] @var{class}]
+@item maint frame-unwinder enable [@code{-all} | @code{-name} @var{name} | [@code{-class}] @var{class}]
+Disable or enable frame unwinders. This is meant only as a testing tool, and
+@value{GDBN} is not guaranteed to work properly if it is unable to find
+valid frame unwinders.
+
+The meaning of each of the invocations are as follows:
+
+@table @samp
+@item @code{-all}
+Disable or enable all unwinders.
+@item @code{-name} @var{name}
+@var{name} is the exact name of the unwinder to be disabled or enabled.
+@item [@code{-class}] @var{class}
+@var{class} is the class of frame unwinders to be disabled or enabled.
+The class may include the prefix @code{FRAME_UNWINDER_}, but it is not
+required.
+@end table
+
+@var{name} and @var{class} are always case insensitive. If no option
+starting wth @code{-} is given, @value{GDBN} assumes @code{-class}.
+
@kindex maint set worker-threads
@kindex maint show worker-threads
@item maint set worker-threads
diff --git a/gdb/dwarf2/frame-tailcall.c b/gdb/dwarf2/frame-tailcall.c
index 54813d00b03..2d7ab740f62 100644
--- a/gdb/dwarf2/frame-tailcall.c
+++ b/gdb/dwarf2/frame-tailcall.c
@@ -321,9 +321,6 @@ tailcall_frame_sniffer (const struct frame_unwind *self,
int next_levels;
struct tailcall_cache *cache;

- if (!dwarf2_frame_unwinders_enabled_p)
- return 0;
-
/* Inner tail call element does not make sense for a sentinel frame. */
next_frame = get_next_frame (this_frame);
if (next_frame == NULL)
diff --git a/gdb/dwarf2/frame.c b/gdb/dwarf2/frame.c
index 3d66ff3d935..4d86557a46b 100644
--- a/gdb/dwarf2/frame.c
+++ b/gdb/dwarf2/frame.c
@@ -183,9 +183,6 @@ static ULONGEST read_encoded_value (struct comp_unit *unit, gdb_byte encoding,
unrelocated_addr func_base);
\f

-/* See dwarf2/frame.h. */
-bool dwarf2_frame_unwinders_enabled_p = true;
-
/* Store the length the expression for the CFA in the `cfa_reg' field,
which is unused in that case. */
#define cfa_exp_len cfa_reg
@@ -1306,9 +1303,6 @@ static int
dwarf2_frame_sniffer (const struct frame_unwind *self,
const frame_info_ptr &this_frame, void **this_cache)
{
- if (!dwarf2_frame_unwinders_enabled_p)
- return 0;
-
/* Grab an address that is guaranteed to reside somewhere within the
function. get_frame_pc(), with a no-return next function, can
end up returning something past the end of this function's body.
@@ -2253,34 +2247,10 @@ dwarf2_build_frame_info (struct objfile *objfile)
set_comp_unit (objfile, unit.release ());
}

-/* Handle 'maintenance show dwarf unwinders'. */
-
-static void
-show_dwarf_unwinders_enabled_p (struct ui_file *file, int from_tty,
- struct cmd_list_element *c,
- const char *value)
-{
- gdb_printf (file,
- _("The DWARF stack unwinders are currently %s.\n"),
- value);
-}
-
void _initialize_dwarf2_frame ();
void
_initialize_dwarf2_frame ()
{
- add_setshow_boolean_cmd ("unwinders", class_obscure,
- &dwarf2_frame_unwinders_enabled_p , _("\
-Set whether the DWARF stack frame unwinders are used."), _("\
-Show whether the DWARF stack frame unwinders are used."), _("\
-When enabled the DWARF stack frame unwinders can be used for architectures\n\
-that support the DWARF unwinders. Enabling the DWARF unwinders for an\n\
-architecture that doesn't support them will have no effect."),
- NULL,
- show_dwarf_unwinders_enabled_p,
- &set_dwarf_cmdlist,
- &show_dwarf_cmdlist);
-
#if GDB_SELF_TEST
selftests::register_test_foreach_arch ("execute_cfa_program",
selftests::execute_cfa_program_test);
diff --git a/gdb/dwarf2/frame.h b/gdb/dwarf2/frame.h
index 2167310fbdf..fe2d669a983 100644
--- a/gdb/dwarf2/frame.h
+++ b/gdb/dwarf2/frame.h
@@ -198,12 +198,6 @@ struct dwarf2_frame_state
bool armcc_cfa_offsets_reversed = false;
};

-/* When this is true the DWARF frame unwinders can be used if they are
- registered with the gdbarch. Not all architectures can or do use the
- DWARF unwinders. Setting this to true on a target that does not
- otherwise support the DWARF unwinders has no effect. */
-extern bool dwarf2_frame_unwinders_enabled_p;
-
/* Set the architecture-specific register state initialization
function for GDBARCH to INIT_REG. */

diff --git a/gdb/frame-unwind.c b/gdb/frame-unwind.c
index 7be01ec2203..f66f233c781 100644
--- a/gdb/frame-unwind.c
+++ b/gdb/frame-unwind.c
@@ -94,6 +94,23 @@ frame_unwinder_class_str (frame_unwind_class uclass)
return location->second;
}

+/* Case insensitive search for a frame_unwind_class based on the given
+ string. */
+static enum frame_unwind_class
+str_to_frame_unwind_class (const char *class_str)
+{
+ const char *prefix = "FRAME_UNWIND_";
+ /* Skip the prefix if present. */
+ if (strncasecmp (class_str, prefix, strlen(prefix)) == 0)
+ class_str += strlen (prefix);
+ for (const auto &it : unwind_class_conversion)
+ {
+ if (strcasecmp (it.second, class_str) == 0)
+ return it.first;
+ }
+ error (_("Unknown frame unwind class: %s"), class_str);
+}
+
void
frame_unwind_prepend_unwinder (struct gdbarch *gdbarch,
const struct frame_unwind *unwinder)
@@ -182,25 +199,47 @@ frame_unwind_find_by_frame (const frame_info_ptr &this_frame, void **this_cache)

const struct frame_unwind *unwinder_from_target;

+ /* If we see a disabled unwinder, we assume some test is being run on
+ GDB, and we don't want to assert at the end of this function. */
+ bool seen_disabled_unwinder = false;
+
unwinder_from_target = target_get_unwinder ();
if (unwinder_from_target != NULL
+ && unwinder_from_target->enabled ()
&& frame_unwind_try_unwinder (this_frame, this_cache,
unwinder_from_target))
return;
+ else if (unwinder_from_target != nullptr
+ && !unwinder_from_target->enabled ())
+ seen_disabled_unwinder = true;

unwinder_from_target = target_get_tailcall_unwinder ();
if (unwinder_from_target != NULL
+ && unwinder_from_target->enabled ()
&& frame_unwind_try_unwinder (this_frame, this_cache,
unwinder_from_target))
return;
+ else if (unwinder_from_target != nullptr
+ && !unwinder_from_target->enabled ())
+ seen_disabled_unwinder = true;

struct gdbarch *gdbarch = get_frame_arch (this_frame);
std::vector<const frame_unwind *> &table = get_frame_unwind_table (gdbarch);
for (auto unwinder : table)
- if (frame_unwind_try_unwinder (this_frame, this_cache, unwinder))
- return;
+ {
+ if (!unwinder->enabled ())
+ {
+ seen_disabled_unwinder = true;
+ continue;
+ }
+ if (frame_unwind_try_unwinder (this_frame, this_cache, unwinder))
+ return;
+ }

- internal_error (_("frame_unwind_find_by_frame failed"));
+ if (seen_disabled_unwinder)
+ error (_("frame_unwind_find_by_frame failed"));
+ else
+ internal_error (_("frame_unwind_find_by_frame failed"));
}

/* A default frame sniffer which always accepts the frame. Used by
@@ -394,10 +433,11 @@ maintenance_info_frame_unwinders (const char *args, int from_tty)
std::vector<const frame_unwind *> &table = get_frame_unwind_table (gdbarch);

ui_out *uiout = current_uiout;
- ui_out_emit_table table_emitter (uiout, 3, -1, "FrameUnwinders");
+ ui_out_emit_table table_emitter (uiout, 4, -1, "FrameUnwinders");
uiout->table_header (27, ui_left, "name", "Name");
uiout->table_header (25, ui_left, "type", "Type");
uiout->table_header (9, ui_left, "class", "Class");
+ uiout->table_header (8, ui_left, "enabled", "Enabled");
uiout->table_body ();

for (auto unwinder : table)
@@ -405,15 +445,97 @@ maintenance_info_frame_unwinders (const char *args, int from_tty)
const char *name = unwinder->name ();
const char *type = frame_type_str (unwinder->type ());
const char *uclass = frame_unwinder_class_str (unwinder->unwinder_class ());
+ const char *enabled = unwinder->enabled () ? "Y" : "N";

ui_out_emit_list tuple_emitter (uiout, nullptr);
uiout->field_string ("name", name);
uiout->field_string ("type", type);
uiout->field_string ("class", uclass);
+ uiout->field_string ("enabled", enabled);
uiout->text ("\n");
}
}

+/* Helper function to both enable and disable frame unwinders.
+ if ENABLE is true, this call will be enabling unwinders,
+ otherwise the unwinders will be disabled. */
+static void
+enable_disable_frame_unwinders (const char *args, int from_tty, bool enable)
+{
+ reinit_frame_cache ();
+ if (args == nullptr)
+ {
+ if (enable)
+ error (_("specify which frame unwinder(s) should be enabled"));
+ else
+ error (_("specify which frame unwinder(s) should be disabled"));
+ }
+ struct gdbarch* gdbarch = current_inferior ()->arch ();
+ std::vector<const frame_unwind *> unwinder_list
+ = gdbarch_unwinder_list (gdbarch);
+
+ /* First see if the user wants to change all unwinders. */
+ if (check_for_argument (&args, "-all"))
+ {
+ for (const frame_unwind *u : unwinder_list)
+ u->set_enabled (enable);
+ return;
+ }
+
+ /* If user entered a specific unwinder name, handle it here. If the
+ unwinder is already at the expected state, error out. */
+ if (check_for_argument (&args, "-name"))
+ {
+ bool did_something = false;
+ for (const frame_unwind *unwinder : unwinder_list)
+ {
+ if (strcasecmp (unwinder->name (), args) == 0)
+ {
+ if (unwinder->enabled () == enable)
+ {
+ if (unwinder->enabled ())
+ error (_("unwinder %s is already enabled"),
+ unwinder->name ());
+ else
+ error (_("unwinder %s is already disabled"),
+ unwinder->name ());
+ }
+ unwinder->set_enabled (enable);
+
+ did_something = true;
+ break;
+ }
+ }
+ if (!did_something)
+ error (_("couldn't find unwinder named %s"),args);
+ }
+ else
+ {
+ /* Discard '-class' argument, if provided. */
+ check_for_argument (&args, "-class");
+ enum frame_unwind_class dclass = str_to_frame_unwind_class (args);
+ for (auto unwinder: unwinder_list)
+ {
+ if (unwinder->unwinder_class () == dclass)
+ unwinder->set_enabled (enable);
+ }
+ }
+}
+
+/* Implement "maint frame-unwinders disable" command. */
+static void
+maintenance_disable_frame_unwinders (const char *args, int from_tty)
+{
+ enable_disable_frame_unwinders (args, from_tty, false);
+}
+
+/* Implement "maint frame-unwinders enable" command. */
+static void
+maintenance_enable_frame_unwinders (const char *args, int from_tty)
+{
+ enable_disable_frame_unwinders (args, from_tty, true);
+}
+
void _initialize_frame_unwind ();
void
_initialize_frame_unwind ()
@@ -425,4 +547,37 @@ _initialize_frame_unwind ()
_("List the frame unwinders currently in effect, "
"starting with the highest priority."),
&maintenanceinfolist);
+
+ /* Add "maint frame-unwinder disable/enable". */
+ static struct cmd_list_element *maint_frame_unwinder;
+
+ add_basic_prefix_cmd ("frame-unwinder", class_maintenance,
+ _("Commands handling frame unwinders."),
+ &maint_frame_unwinder, 0, &maintenancelist);
+
+ add_cmd ("disable", class_maintenance, maintenance_disable_frame_unwinders,
+ _("\
+Disable one or more frame unwinder(s).\n\
+Usage: maint frame-unwinder disable [-all | -name NAME | [-class] CLASS]\n\
+\n\
+These are the meanings of the options:\n\
+\t-all - All available unwinders will be disabled\n\
+\t-name - NAME is the exact name of the frame unwinder to be disabled\n\
+\t-class - CLASS is the class of unwinders to be disabled.\n\
+\n\
+UNWINDER and NAME are case insensitive."),
+ & maint_frame_unwinder);
+
+ add_cmd ("enable", class_maintenance, maintenance_enable_frame_unwinders,
+ _("\
+Enable one or more frame unwinder(s).\n\
+Usage: maint frame-unwinder enable [-all | -name NAME | [-class] CLASS]\n\
+\n\
+These are the meanings of the options:\n\
+\t-all - All available unwinders will be enabled\n\
+\t-name - NAME is the exact name of the frame unwinder to be enabled\n\
+\t-class - CLASS is the class of unwinders to be enabled.\n\
+\n\
+UNWINDER and NAME are case insensitive."),
+ & maint_frame_unwinder);
}
diff --git a/gdb/frame-unwind.h b/gdb/frame-unwind.h
index b078945a200..f5ea8d9f690 100644
--- a/gdb/frame-unwind.h
+++ b/gdb/frame-unwind.h
@@ -180,6 +180,9 @@ class frame_unwind
unwinding. */
enum frame_unwind_class m_unwinder_class;
const struct frame_data *m_unwind_data;
+
+ /* Whether this unwinder can be used when sniffing. */
+ mutable bool m_enabled = true;
public:
frame_unwind (const char *name, frame_type type, frame_unwind_class uclass,
const struct frame_data *data)
@@ -207,6 +210,16 @@ class frame_unwind
return m_unwind_data;
}

+ bool enabled () const
+ {
+ return m_enabled;
+ }
+
+ void set_enabled (bool state) const
+ {
+ m_enabled = state;
+ }
+
/* Default stop_reason function. It reports NO_REASON, unless the
frame is the outermost. */
virtual enum unwind_stop_reason stop_reason (const frame_info_ptr &this_frame,
diff --git a/gdb/testsuite/gdb.base/frame-info-consistent.exp b/gdb/testsuite/gdb.base/frame-info-consistent.exp
index fe0cfad95bc..d4a21300ce3 100644
--- a/gdb/testsuite/gdb.base/frame-info-consistent.exp
+++ b/gdb/testsuite/gdb.base/frame-info-consistent.exp
@@ -95,11 +95,11 @@ proc compare_frames {frames} {
}
}

-proc test {dwarf_unwinder} {
+proc test {enable} {

clean_restart $::binfile

- gdb_test_no_output "maint set dwarf unwinder $dwarf_unwinder"
+ gdb_test_no_output "maint frame-unwinder $enable DEBUGINFO"

if {![runto_main]} {
return 0
@@ -134,6 +134,6 @@ proc test {dwarf_unwinder} {
}
}

-foreach_with_prefix dwarf {"off" "on"} {
+foreach_with_prefix dwarf {"disable" "enable"} {
test $dwarf
}
diff --git a/gdb/testsuite/gdb.base/frame-unwind-disable.c b/gdb/testsuite/gdb.base/frame-unwind-disable.c
new file mode 100644
index 00000000000..078517c011e
--- /dev/null
+++ b/gdb/testsuite/gdb.base/frame-unwind-disable.c
@@ -0,0 +1,21 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+ Copyright 2024 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/>. */
+
+int main ()
+{
+ return 0;
+}
diff --git a/gdb/testsuite/gdb.base/frame-unwind-disable.exp b/gdb/testsuite/gdb.base/frame-unwind-disable.exp
new file mode 100644
index 00000000000..972d6b70351
--- /dev/null
+++ b/gdb/testsuite/gdb.base/frame-unwind-disable.exp
@@ -0,0 +1,140 @@
+# Copyright 2024 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/>.
+
+# Test multiple situations in which we may use the maintenance command to
+# disable and enable frame unwinders, and check that they really are
+# disabled when they say the are.
+
+standard_testfile .c
+
+# Proc to check if the unwinder of the given name is in the desired state.
+# STATE can be either Y or N.
+proc check_unwinder_state { unwinder_name state {testname ""} } {
+ set should_pass false
+ set command "maint info frame-unwinders"
+ if {${testname} == ""} {
+ set testname "checking state ${state} for ${unwinder_name}"
+ }
+ gdb_test_multiple "${command}" "${testname}" -lbl {
+ -re "^${unwinder_name}\\s+\\w+\\s+\\w+\\s+${state}\\s+" {
+ set should_pass true
+ exp_continue
+ }
+ -re "${command}" {
+ exp_continue
+ }
+ -re "\\w+\\s+\\w+\\s+\\w+\\s+\\w+\\s+" {
+ exp_continue
+ }
+ -re "${::gdb_prompt} $" {
+ # We can't use -wrap here because it expects the line with start
+ # with \r\n, but the previous commands eat that
+ gdb_assert {${should_pass} == true} "${gdb_test_name}"
+ }
+ }
+}
+
+proc check_unwinder_class { unwinder_class state {testname ""} } {
+ set command "maint info frame-unwinders"
+ set seen_arches 0
+ set correct_state 0
+ if {$testname == ""} {
+ set testname "checking if ${unwinder_class} state is ${state}"
+ }
+ gdb_test_multiple "${command}" "${testname}" -lbl {
+ -re "^\[^\r\n\]+\\s+\\w+\\s+${unwinder_class}\\s+\(\[YN\]\)\\s+\r\n" {
+ # The unwinder name may have multiple words, so we need to use the
+ # more generic [^\r\n] pattern to match the unwinders.
+ set should_pass true
+ incr seen_arches
+ set cur_state $expect_out(1,string)
+ if {$cur_state == $state} {
+ incr correct_state
+ }
+ exp_continue
+ }
+ -re "${command}" {
+ exp_continue
+ }
+ -re "\[^\r\n\]+\r\n" {
+ exp_continue
+ }
+ -re "${::gdb_prompt} $" {
+ gdb_assert {${correct_state} == ${seen_arches}} "${gdb_test_name}"
+ }
+ }
+}
+
+if {[prepare_for_testing "failed to prepare" ${testfile} ${srcfile} ]} {
+ return -1
+}
+
+if {![runto_main]} {
+ untested "couldn't run to main"
+ return
+}
+
+# Test disabling all unwinders
+check_unwinder_class "\\w+" "Y" \
+ "Checking all unwinders before any changes"
+gdb_test_no_output "maint frame-unwinder disable -all"
+check_unwinder_class "\\w+" "N" \
+ "Checking all unwinders were properly disabled"
+
+# Test if GDB can still make a backtrace once all unwinders are disabled.
+# It should be impossible.
+gdb_test "backtrace" ".*frame_unwind_find_by_frame failed.*" \
+ "confirm that no suitable unwinders are found"
+
+# Reenable all unwinders
+gdb_test_no_output "maint frame-unwinder enable -all"
+check_unwinder_class "\\w+" "Y" \
+ "Checking all unwinders after re-enabling them all"
+
+# Check that we are able to get backtraces once again.
+gdb_test "backtrace" ".0\\s+main .. at.*" \
+ "confirm we now get usable backtraces"
+
+# Check if we can disable an unwinder based on the name.
+check_unwinder_state "dummy" "Y"
+gdb_test_no_output "maint frame-unwinder disable -name dummy"
+check_unwinder_state "dummy" "N"
+# And verify what happens if you try to disable it again.
+gdb_test "maint frame-unwinder disable -name dummy" \
+ "unwinder dummy is already disabled" \
+ "disable already disabled unwinder"
+check_unwinder_state "dummy" "N" "check if dummy continues disabled"
+
+foreach class {GDB ARCH DEBUGINFO EXTENSION} {
+ # Disable all unwinders of type CLASS, and check that the command worked.
+ gdb_test_no_output "maint frame-unwinder disable ${class}"
+ check_unwinder_class "${class}" "N"
+}
+
+# Now check if we are able to enable a single unwinder, and what happens if we
+# enable it twice.
+gdb_test_no_output "maint frame-unwinder enable -name dummy"
+check_unwinder_state "dummy" "Y" "successfully enabled dummy unwinder"
+gdb_test "maint frame-unwinder enable -name dummy" \
+ "unwinder dummy is already enabled" \
+ "enable already enabled unwinder"
+check_unwinder_state "dummy" "Y" "check if dummy continues enabled"
+
+foreach class {GDB ARCH DEBUGINFO EXTENSION} {
+ # Enable all unwinders of type CLASS, and check that the command worked.
+ # using "-class" option to ensure it works. Should make no difference.
+ gdb_test_no_output "maint frame-unwinder enable -class ${class}"
+ check_unwinder_class "${class}" "Y"
+}
diff --git a/gdb/testsuite/gdb.base/maint.exp b/gdb/testsuite/gdb.base/maint.exp
index d6aa22321f1..62f8ad1d1f3 100644
--- a/gdb/testsuite/gdb.base/maint.exp
+++ b/gdb/testsuite/gdb.base/maint.exp
@@ -451,10 +451,6 @@ gdb_test_no_output "maint info line-table xxx.c" \

set timeout $oldtimeout

-# Just check that the DWARF unwinders control flag is visible.
-gdb_test "maint show dwarf unwinders" \
- "The DWARF stack unwinders are currently (on|off)\\."
-
#============test help on maint commands

test_prefix_command_help {"maint info" "maintenance info"} {
--
2.46.2