[PATCH] Fix reverse stepping multiple contiguous PC ranges over the line table.

Carl Love via Gdb-patches
2023-04-27T21:00:31Z

GDB maintainers:

The following patch fixes issues on PowerPC with the reverse-step and
reverse-next instructions when there are multiple assignment statements
on the same line and when there are multiple function calls on the same
line. The commit log below discusses these issues in further depth.
The discussion included what the correct operation should be for these
commands based on the GDB documentation. The proposed patch at that
time changed how the commands worked on other platforms such as X86 in
a way they no longer matched the documentation.

The issue is the line table contains multiple entries for the same
source line. The patch adds a function to search the line table to
find the address of the first instruction of a line. When setup up the
reverse stepping range, the function is called to make sure the start
of the range corresponds to the address of the first instruction for
the line.

The following patch fixes the execution of the reveres-step and
reverse-next commands for both senarios of multiple statements on the
same line for PowerPC and aarch64-linux. Unlike the previous patch, it
does not change the operation of the commands on other platforms, i.e.
X86. The patch adds new test cases for both scenarios to verify they
work correctly.

The patch has been tested on PowerPC, Intel X86 and aarch64-linux with
no new regression failures.

Please let me know if the patch is acceptable for mainline. Thanks.

Carl

---------------------------------------------------------------
Fix reverse stepping multiple contiguous PC ranges over the line table.

There are a couple of scenarios where the GDB reverse-step and reverse-next
commands do not work correctly. The first scenario consists of multiple
assignment statements on the same line. A patch was proposed to address the
issue by Luis Machado and briefly discussed on the mailing list in Feb 2021.

https://sourceware.org/pipermail/gdb-patches/2021-February/175678.html

The discussion was revived by Carl Love with regards to fixing the same
issue on PowerPC.

https://sourceware.org/pipermail/gdb-patches/2022-March/186463.html

The patch was not completed and has been on Carl's to do list for some time.

Discussion of a patch to change how the reverse-step and reverse-next
commands submitted by Carl Love was started in thread:

https://sourceware.org/pipermail/gdb-patches/2023-January/195563.html

The patch was withdrawn as it was pointed out the proposed patch would
change the intended behavior of the commands as documented in the GDB
manual. However, it was pointed out by Pedro Alves <pedro@palves.net>
that the reverse-step and reverse-next commands do not work when there
are multiple function calls on the same line. This is a second scenario
where the commands do not work correctly.

The following patch is an extended version of the original patch by
Luis Machado to fix the issues in scenario 1 to also address the issues in
scenario 2.

--------------------------------------------------------

Scenario 1 issue description by Luis Machado:

When running GDB's testsuite on aarch64-linux/Ubuntu 20.04 (also spotted on
the ppc backend), I noticed some failures in gdb.reverse/solib-precsave.exp
and gdb.reverse/solib-reverse.exp.

The failure happens around the following code:

38 b[1] = shr2(17); /* middle part two */
40 b[0] = 6; b[1] = 9; /* generic statement, end part two */
42 shr1 ("message 1\n"); /* shr1 one */

Normal execution:

- step from line 38 will land on line 40.
- step from line 40 will land on line 42.

Reverse execution:
- step from line 42 will land on line 40.
- step from line 40 will land on line 40.
- step from line 40 will land on line 38.

The problem here is that line 40 contains two contiguous but distinct
PC ranges in the line table, like so:

Line 40 - [0x7ec ~ 0x7f4]
Line 40 - [0x7f4 ~ 0x7fc]

The two distinct ranges are generated because GCC started outputting source
column information, which GDB doesn't take into account at the moment.

When stepping forward from line 40, we skip both of these ranges and land on
line 42. When stepping backward from line 42, we stop at the start PC of the
second (or first, going backwards) range of line 40.

This happens because we have this check in infrun.c:process_event_stop_test:

/* When stepping backward, stop at beginning of line range
(unless it's the function entry point, in which case
keep going back to the call point). */
CORE_ADDR stop_pc = ecs->event_thread->stop_pc ();
if (stop_pc == ecs->event_thread->control.step_range_start
&& stop_pc != ecs->stop_func_start
&& execution_direction == EXEC_REVERSE)
end_stepping_range (ecs);
else
keep_going (ecs);

Since we've reached ecs->event_thread->control.step_range_start, we stop
stepping backwards.

The right thing to do is to look for adjacent PC ranges for the same line,
until we notice a line change. Then we take that as the start PC of the
range.

Another solution I thought about is to merge the contiguous ranges when
we are reading the line tables. Though I'm not sure if we really want to
process that data as opposed to keeping it as the compiler created, and
then working around that.

The test case gdb.reverse/map-to-same-line.exp is added to test the fix
for the issues in scenario 1.

---------------------------------------------------------

Scenario 2 issue described by Pedro Alves:

The following explanation of the issue was taken from the gdb mailing list
discussion of the withdrawn patch to change the behavior of the reverse-step
and reverse-next commands. Specifically, message from Pedro Alves
<pedro@palves.net> where he demonstrates the issue where you have multiple
function calls on the same source code line:

https://sourceware.org/pipermail/gdb-patches/2023-January/196110.html

The source line looks like:

func1 (); func2 ();

so stepping backwards over that line should always stop at the first
instruction of the line, not in the middle. Let's simplify this.

Here's the full source code of my example:

(gdb) list 1
1 void func1 ()
2 {
3 }
4
5 void func2 ()
6 {
7 }
8
9 int main ()
10 {
11 func1 (); func2 ();
12 }

Compiled with:

$ gcc reverse.c -o reverse -g3 -O0
$ gcc -v
...
gcc version 11.3.0 (Ubuntu 11.3.0-1ubuntu1~22.04)

Now let's debug it with target record, using current gdb git master (f3d8ae90b236),
without your patch:

$ gdb ~/reverse
GNU gdb (GDB) 14.0.50.20230124-git
...
Reading symbols from /home/pedro/reverse...
(gdb) start
Temporary breakpoint 1 at 0x1147: file reverse.c, line 11.
Starting program: /home/pedro/reverse
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".

Temporary breakpoint 1, main () at reverse.c:11
11 func1 (); func2 ();
(gdb) record

(gdb) disassemble /s
Dump of assembler code for function main:
reverse.c:
10 {
0x000055555555513f <+0>: endbr64
0x0000555555555143 <+4>: push %rbp
0x0000555555555144 <+5>: mov %rsp,%rbp

11 func1 (); func2 ();
=> 0x0000555555555147 <+8>: mov $0x0,%eax
0x000055555555514c <+13>: call 0x555555555129 <func1>
0x0000555555555151 <+18>: mov $0x0,%eax
0x0000555555555156 <+23>: call 0x555555555134 <func2>
0x000055555555515b <+28>: mov $0x0,%eax

12 }
0x0000555555555160 <+33>: pop %rbp
0x0000555555555161 <+34>: ret
End of assembler dump.

(gdb) n
12 }

So far so good, a "next" stepped over the whole of line 11 and stopped at line 12.

Let's confirm where we are now:

(gdb) disassemble /s
Dump of assembler code for function main:
reverse.c:
10 {
0x000055555555513f <+0>: endbr64
0x0000555555555143 <+4>: push %rbp
0x0000555555555144 <+5>: mov %rsp,%rbp

11 func1 (); func2 ();
0x0000555555555147 <+8>: mov $0x0,%eax
0x000055555555514c <+13>: call 0x555555555129 <func1>
0x0000555555555151 <+18>: mov $0x0,%eax
0x0000555555555156 <+23>: call 0x555555555134 <func2>
0x000055555555515b <+28>: mov $0x0,%eax

12 }
=> 0x0000555555555160 <+33>: pop %rbp
0x0000555555555161 <+34>: ret
End of assembler dump.

Good, we're at the first instruction of line 12.

Now let's undo the "next", with "reverse-next":

(gdb) reverse-next
11 func1 (); func2 ();

Seemingly stopped at line 11. Let's see exactly where:

(gdb) disassemble /s
Dump of assembler code for function main:
reverse.c:
10 {
0x000055555555513f <+0>: endbr64
0x0000555555555143 <+4>: push %rbp
0x0000555555555144 <+5>: mov %rsp,%rbp

11 func1 (); func2 ();
0x0000555555555147 <+8>: mov $0x0,%eax
0x000055555555514c <+13>: call 0x555555555129 <func1>
=> 0x0000555555555151 <+18>: mov $0x0,%eax
0x0000555555555156 <+23>: call 0x555555555134 <func2>
0x000055555555515b <+28>: mov $0x0,%eax

12 }
0x0000555555555160 <+33>: pop %rbp
0x0000555555555161 <+34>: ret
End of assembler dump.
(gdb)

And lo, we stopped in the middle of line 11! That is a bug, we should have
stepped back all the way to the beginning of the line. The "reverse-next"
should have fully undone the prior "next" command.

The test cases gdb.reverse/func-map-to-same-line-no-colum-info.exp and
gdb.reverse/func-map-to-same-line.exp were added to test the fix for scenario
2 when the binary was compiled with and without line table information.

bug: https://sourceware.org/bugzilla/show_bug.cgi?id=28426

Co-authored-by: Luis Machado <luis.machado@arm.com>
Co-authored-by: Carl Love <cel@us.ibm.com>
---
gdb/infrun.c | 57 +++++++
gdb/symtab.c | 49 ++++++
gdb/symtab.h | 16 ++
.../func-map-to-same-line-no-column-info.exp | 135 ++++++++++++++++
.../gdb.reverse/func-map-to-same-line.c | 36 +++++
.../gdb.reverse/func-map-to-same-line.exp | 123 ++++++++++++++
gdb/testsuite/gdb.reverse/map-to-same-line.c | 58 +++++++
.../gdb.reverse/map-to-same-line.exp | 153 ++++++++++++++++++
8 files changed, 627 insertions(+)
create mode 100644 gdb/testsuite/gdb.reverse/func-map-to-same-line-no-column-info.exp
create mode 100644 gdb/testsuite/gdb.reverse/func-map-to-same-line.c
create mode 100644 gdb/testsuite/gdb.reverse/func-map-to-same-line.exp
create mode 100644 gdb/testsuite/gdb.reverse/map-to-same-line.c
create mode 100644 gdb/testsuite/gdb.reverse/map-to-same-line.exp

diff --git a/gdb/infrun.c b/gdb/infrun.c
index 2f1c6cd694b..59374a05471 100644
--- a/gdb/infrun.c
+++ b/gdb/infrun.c
@@ -113,6 +113,9 @@ static struct async_event_handler *infrun_async_inferior_event_token;
Starts off as -1, indicating "never enabled/disabled". */
static int infrun_is_async = -1;

+static CORE_ADDR update_line_range_start (CORE_ADDR pc,
+ struct execution_control_state *ecs);
+
/* See infrun.h. */

void
@@ -6768,6 +6771,25 @@ handle_signal_stop (struct execution_control_state *ecs)
process_event_stop_test (ecs);
}

+CORE_ADDR
+update_line_range_start (CORE_ADDR pc, struct execution_control_state *ecs)
+{
+ /* The line table may have multiple entries for the same source code line.
+ Given the PC, check the line table and return the PC that corresponds
+ to the line table entry for the source line that PC is in. */
+ CORE_ADDR start_line_pc = ecs->event_thread->control.step_range_start;
+ gdb::optional<CORE_ADDR> real_range_start;
+
+ /* Call find_line_range_start to get smallest address in the
+ linetable for multiple Line X entries in the line table. */
+ real_range_start = find_line_range_start (pc);
+
+ if (real_range_start.has_value ())
+ start_line_pc = *real_range_start;
+
+ return start_line_pc;
+}
+
/* Come here when we've got some debug event / signal we can explain
(IOW, not a random signal), and test whether it should cause a
stop, or whether we should resume the inferior (transparently).
@@ -7569,6 +7591,28 @@ process_event_stop_test (struct execution_control_state *ecs)

if (stop_pc_sal.is_stmt)
{
+ if (execution_direction == EXEC_REVERSE)
+ {
+ /* We are stepping backwards make sure we have reached the
+ beginning of the line. */
+ CORE_ADDR stop_pc = ecs->event_thread->stop_pc ();
+ CORE_ADDR start_line_pc
+ = update_line_range_start (stop_pc, ecs);
+
+ if (stop_pc != start_line_pc)
+ {
+ /* Have not reached the beginning of the source code line.
+ Set a step range. Execution should stop in any function
+ calls we execute back into before reaching the beginning
+ of the line. */
+ ecs->event_thread->control.step_range_start = start_line_pc;
+ ecs->event_thread->control.step_range_end = stop_pc;
+ set_step_info (ecs->event_thread, frame, stop_pc_sal);
+ keep_going (ecs);
+ return;
+ }
+ }
+
/* We are at the start of a statement.

So stop. Note that we don't stop if we step into the middle of a
@@ -7631,6 +7675,19 @@ process_event_stop_test (struct execution_control_state *ecs)
set_step_info (ecs->event_thread, frame, stop_pc_sal);

infrun_debug_printf ("keep going");
+
+ if (execution_direction == EXEC_REVERSE)
+ {
+ CORE_ADDR stop_pc = ecs->event_thread->stop_pc ();
+
+ /* Make sure the stop_pc is set to the beginning of the line. */
+ if (stop_pc != ecs->event_thread->control.step_range_start)
+ {
+ stop_pc = update_line_range_start (stop_pc, ecs);
+ ecs->event_thread->control.step_range_start = stop_pc;
+ }
+ }
+
keep_going (ecs);
}

diff --git a/gdb/symtab.c b/gdb/symtab.c
index 27611a34ec4..91d35616eb9 100644
--- a/gdb/symtab.c
+++ b/gdb/symtab.c
@@ -3282,6 +3282,55 @@ find_pc_line (CORE_ADDR pc, int notcurrent)
return sal;
}

+/* Compare two symtab_and_line entries. Return true if both have
+ the same line number and the same symtab pointer. That means we
+ are dealing with two entries from the same line and from the same
+ source file.
+
+ Return false otherwise. */
+
+static bool
+sal_line_symtab_matches_p (const symtab_and_line &sal1,
+ const symtab_and_line &sal2)
+{
+ return (sal1.line == sal2.line && sal1.symtab == sal2.symtab);
+}
+
+/* See symtah.h. */
+
+gdb::optional<CORE_ADDR>
+find_line_range_start (CORE_ADDR pc)
+{
+ struct symtab_and_line current_sal = find_pc_line (pc, 0);
+
+ if (current_sal.line == 0)
+ return {};
+
+ struct symtab_and_line prev_sal = find_pc_line (current_sal.pc - 1, 0);
+
+ /* If the previous entry is for a different line, that means we are already
+ at the entry with the start PC for this line. */
+ if (!sal_line_symtab_matches_p (prev_sal, current_sal))
+ return current_sal.pc;
+
+ /* Otherwise, keep looking for entries for the same line but with
+ smaller PC's. */
+ bool done = false;
+ CORE_ADDR prev_pc;
+ while (!done)
+ {
+ prev_pc = prev_sal.pc;
+
+ prev_sal = find_pc_line (prev_pc - 1, 0);
+
+ /* Did we notice a line change? If so, we are done with the search. */
+ if (!sal_line_symtab_matches_p (prev_sal, current_sal))
+ done = true;
+ }
+
+ return prev_pc;
+}
+
/* See symtab.h. */

struct symtab *
diff --git a/gdb/symtab.h b/gdb/symtab.h
index 404d0ab30a8..f54305636da 100644
--- a/gdb/symtab.h
+++ b/gdb/symtab.h
@@ -2346,6 +2346,22 @@ extern struct symtab_and_line find_pc_line (CORE_ADDR, int);
extern struct symtab_and_line find_pc_sect_line (CORE_ADDR,
struct obj_section *, int);

+/* Given PC, and assuming it is part of a range of addresses that is part of a
+ line, go back through the linetable and find the starting PC of that
+ line.
+
+ For example, suppose we have 3 PC ranges for line X:
+
+ Line X - [0x0 - 0x8]
+ Line X - [0x8 - 0x10]
+ Line X - [0x10 - 0x18]
+
+ If we call the function with PC == 0x14, we want to return 0x0, as that is
+ the starting PC of line X, and the ranges are contiguous.
+*/
+
+extern gdb::optional<CORE_ADDR> find_line_range_start (CORE_ADDR pc);
+
/* Wrapper around find_pc_line to just return the symtab. */

extern struct symtab *find_pc_line_symtab (CORE_ADDR);
diff --git a/gdb/testsuite/gdb.reverse/func-map-to-same-line-no-column-info.exp b/gdb/testsuite/gdb.reverse/func-map-to-same-line-no-column-info.exp
new file mode 100644
index 00000000000..20529c90fc2
--- /dev/null
+++ b/gdb/testsuite/gdb.reverse/func-map-to-same-line-no-column-info.exp
@@ -0,0 +1,135 @@
+# Copyright 2008-2023 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/>. */
+
+# This file is part of the GDB testsuite. It tests reverse stepping.
+# Lots of code borrowed from "step-test.exp".
+
+# This test checks to make sure there is no regression failures for
+# the reverse-next command when stepping back over two functions in
+# the same line.
+
+if ![supports_reverse] {
+ return
+}
+
+# This test uses the gcc no-column-info command.
+if ![is_c_compiler_gcc] {
+ unsupported "gcc is required for this test"
+ return 0
+}
+
+set srcfile func-map-to-same-line.c
+set executable func-map-to-same-line
+
+set options [list debug additional_flags=-gno-column-info]
+
+if {[build_executable "failed to prepare" $executable $srcfile $options] == -1}\
+ {
+ return -1
+}
+
+clean_restart $executable
+
+runto_main
+set target_remote [gdb_is_target_remote]
+
+if [supports_process_record] {
+ # Activate process record/replay.
+ gdb_test_no_output "record" "turn on process record for test1"
+}
+
+# This regression test verifies the reverse-step and reverse-next commands
+# work properly when executing backwards thru a source line containing
+# two function calls on the same source line, i.e. func1 (); func2 ();
+# This test is compiled so the dwarf info not contain the line table
+# information.
+
+# Test 1, reverse-next command
+# Set breakpoint at the line after the function calls.
+set bp_start_reverse_test [gdb_get_line_number "START REVERSE TEST" $srcfile]
+gdb_breakpoint $srcfile:$bp_start_reverse_test temporary
+
+# Continue to break point for reverse-next test.
+# Command definition: reverse-next [count]
+# Run backward to the beginning of the previous line executed in the current
+# (innermost) stack frame. If the line contains function calls, they will be
+# “un-executed” without stopping. Starting from the first line of a function,
+# reverse-next will take you back to the caller of that function, before the
+# function was called, just as the normal next command would take you from
+# the last line of a function back to its return to its caller 2 .
+
+gdb_continue_to_breakpoint \
+ "stopped at command reverse-next test start location" \
+ ".*$srcfile:$bp_start_reverse_test\r\n.*"
+
+# The reverse-next should step all the way back to the beginning of the line,
+# i.e. at the beginning of the func1 call.
+gdb_test "reverse-next" ".*func1 \\(\\); func2 \\(\\);.*" \
+ "reverse-next to line with two functions"
+
+# A reverse-step should step back and stop at the beginning
+# of the previous line b = 2, i.e. not in func1 ().
+gdb_test "reverse-step" ".*b = 2;.*" \
+ "reverse-step to previous line b = 2"
+
+
+# Setup for test 2
+# Go back to the start of the function
+gdb_test "reverse-continue" "a = 1;" "At start of main, setup for test 2"
+
+# Turn off record to clear logs and turn on again
+gdb_test "record stop" "Process record is stopped.*" \
+ "turn off process record for test1"
+gdb_test_no_output "record" "turn on process record for test2"
+
+# Delete all breakpoints and catchpoints.
+delete_breakpoints
+
+
+# Test 2, reverse-step command
+# Set breakpoint at the line after the function calls.
+gdb_breakpoint $srcfile:$bp_start_reverse_test temporary
+
+# Continue to the start of the reverse-step test.
+# Command definition: reverse-step [count]
+# Run the program backward until control reaches the start of a
+# different source line; then stop it, and return control to gdb.
+# Like the step command, reverse-step will only stop at the beginning of a
+# source line. It “un-executes” the previously executed source line. If the
+# previous source line included calls to debuggable functions, reverse-step
+# will step (backward) into the called function, stopping at the beginning
+# of the last statement in the called function (typically a return
+# statement). Also, as with the step command, if non-debuggable functions
+# are called, reverse-step will run thru them backward without stopping.
+
+gdb_continue_to_breakpoint \
+ "stopped at command reverse-step test start location" \
+ ".*$srcfile:$bp_start_reverse_test\r\n.*"
+
+# The first reverse step should take us call of func2 ().
+gdb_test "reverse-step" ".*}.*" \
+ "reverse-step into func2 "
+
+# The second reverse step should take us into func1 ().
+gdb_test "reverse-step" ".*}.*" \
+ "reverse-step into func1 "
+
+# The third reverse step should take us call of func1 ().
+gdb_test "reverse-step" ".*func1 \\(\\); func2 \\(\\);.*" \
+ "reverse-step to line func1(); func2(), at call for func1 "
+
+# The fourth reverse step should take us to b = 2 ().
+gdb_test "reverse-step" ".*b = 2;.*" \
+ "reverse-step to line b = 2 "
diff --git a/gdb/testsuite/gdb.reverse/func-map-to-same-line.c b/gdb/testsuite/gdb.reverse/func-map-to-same-line.c
new file mode 100644
index 00000000000..e9787ef9ff5
--- /dev/null
+++ b/gdb/testsuite/gdb.reverse/func-map-to-same-line.c
@@ -0,0 +1,36 @@
+/* Copyright 2008-2023 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/>.
+
+ This test is used to test the reverse-step and reverse-next instruction
+ execution for a source line that contains multiple function calls. */
+
+void
+func1 ()
+{
+}
+
+void
+func2 ()
+{
+}
+
+int main ()
+{
+ int a, b;
+ a = 1;
+ b = 2;
+ func1 (); func2 ();
+ a = a + b; // START REVERSE TEST
+}
diff --git a/gdb/testsuite/gdb.reverse/func-map-to-same-line.exp b/gdb/testsuite/gdb.reverse/func-map-to-same-line.exp
new file mode 100644
index 00000000000..b632a236bbe
--- /dev/null
+++ b/gdb/testsuite/gdb.reverse/func-map-to-same-line.exp
@@ -0,0 +1,123 @@
+# Copyright 2008-2023 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/>. */
+
+# This file is part of the GDB testsuite. It tests reverse stepping.
+# Lots of code borrowed from "step-test.exp".
+
+# This test checks to make sure there is no regression failures for
+# the reverse-next command when stepping back over two functions in
+# the same line.
+
+if ![supports_reverse] {
+ return
+}
+
+standard_testfile
+
+if { [prepare_for_testing "failed to prepare" $testfile $srcfile] } {
+ return -1
+}
+
+runto_main
+set target_remote [gdb_is_target_remote]
+
+if [supports_process_record] {
+ # Activate process record/replay.
+ gdb_test_no_output "record" "turn on process record for test1"
+}
+
+# This regression test verifies the reverse-step and reverse-next commands
+# work properly when executing backwards thru a source line containing
+# two function calls on the same source line, i.e. func1 (); func2 ();
+# The assumption for this test is the dwarf info contain the column
+# information.
+
+# Test 1, reverse-next command
+# Set breakpoint at the line after the function calls.
+set bp_start_reverse_test [gdb_get_line_number "START REVERSE TEST" $srcfile]
+gdb_breakpoint $srcfile:$bp_start_reverse_test temporary
+
+# Continue to break point for reverse-next test.
+# Command definition: reverse-next [count]
+# Run backward to the beginning of the previous line executed in the current
+# (innermost) stack frame. If the line contains function calls, they will be
+# “un-executed” without stopping. Starting from the first line of a function,
+# reverse-next will take you back to the caller of that function, before the
+# function was called, just as the normal next command would take you from
+# the last line of a function back to its return to its caller 2 .
+
+gdb_continue_to_breakpoint \
+ "stopped at command reverse-next test start location" \
+ ".*$srcfile:$bp_start_reverse_test\r\n.*"
+
+# The reverse-next should step all the way back to the beginning of the line,
+# i.e. at the beginning of the func1 call.
+gdb_test "reverse-next" ".*func1 \\(\\); func2 \\(\\);.*" \
+ "reverse-next to line with two functions"
+
+# A reverse-step should step back and stop at the beginning
+# of the previous line b = 2, i.e. not in func1 ().
+gdb_test "reverse-step" ".*b = 2;.*" \
+ "reverse-step to previous line b = 2"
+
+
+# Setup for test 2
+# Go back to the start of the function
+gdb_test "reverse-continue" "a = 1;" "At start of main, setup for test 2"
+
+# Turn off record to clear logs and turn on again
+gdb_test "record stop" "Process record is stopped.*" \
+ "turn off process record for test1"
+gdb_test_no_output "record" "turn on process record for test2"
+
+# Delete all breakpoints and catchpoints.
+delete_breakpoints
+
+
+# Test 2, reverse-step command
+# Set breakpoint at the line after the function calls.
+gdb_breakpoint $srcfile:$bp_start_reverse_test temporary
+
+# Continue to the start of the reverse-step test.
+# Command definition: reverse-step [count]
+# Run the program backward until control reaches the start of a
+# different source line; then stop it, and return control to gdb.
+# Like the step command, reverse-step will only stop at the beginning of a
+# source line. It “un-executes” the previously executed source line. If the
+# previous source line included calls to debuggable functions, reverse-step
+# will step (backward) into the called function, stopping at the beginning
+# of the last statement in the called function (typically a return
+# statement). Also, as with the step command, if non-debuggable functions
+# are called, reverse-step will run thru them backward without stopping.
+
+gdb_continue_to_breakpoint \
+ "stopped at command reverse-step test start location" \
+ ".*$srcfile:$bp_start_reverse_test\r\n.*"
+
+# The first reverse step should take us call of func2 ().
+gdb_test "reverse-step" ".*}.*" \
+ "reverse-step into func2 "
+
+# The second reverse step should take us into func1 ().
+gdb_test "reverse-step" ".*}.*" \
+ "reverse-step into func1 "
+
+# The third reverse step should take us call of func1 ().
+gdb_test "reverse-step" ".*func1 \\(\\); func2 \\(\\);.*" \
+ "reverse-step to line func1(); func2(), at call for func1 "
+
+# The fourth reverse step should take us to b = 2 ().
+gdb_test "reverse-step" ".*b = 2;.*" \
+ "reverse-step to line b = 2 "
diff --git a/gdb/testsuite/gdb.reverse/map-to-same-line.c b/gdb/testsuite/gdb.reverse/map-to-same-line.c
new file mode 100644
index 00000000000..f20d778f40e
--- /dev/null
+++ b/gdb/testsuite/gdb.reverse/map-to-same-line.c
@@ -0,0 +1,58 @@
+/* Copyright 2008-2023 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/ >. */
+
+/* The purpose of this test is to create a DWARF line table that contains two
+ or more entries for the same line. When stepping (forwards or backwards),
+ GDB should step over the entire line and not just a particular entry in the
+ line table. */
+
+int
+main ()
+{ /* TAG: main prologue */
+ asm ("main_label: .globl main_label");
+ int i = 1, j = 2, k;
+ float f1 = 2.0, f2 = 4.1, f3;
+ const char *str_1 = "foo", *str_2 = "bar", *str_3;
+
+ asm ("line1: .globl line1");
+ k = i; f3 = f1; str_3 = str_1; /* TAG: line 1 */
+
+ asm ("line2: .globl line2");
+ k = j; f3 = f2; str_3 = str_2; /* TAG: line 2 */
+
+ asm ("line3: .globl line3");
+ k = i; f3 = f1; str_3 = str_1; /* TAG: line 3 */
+
+ asm ("line4: .globl line4");
+ k = j; f3 = f2; str_3 = str_2; /* TAG: line 4 */
+
+ asm ("line5: .globl line5");
+ k = i; f3 = f1; str_3 = str_1; /* TAG: line 5 */
+
+ asm ("line6: .globl line6");
+ k = j; f3 = f2; str_3 = str_2; /* TAG: line 6 */
+
+ asm ("line7: .globl line7");
+ k = i; f3 = f1; str_3 = str_1; /* TAG: line 7 */
+
+ asm ("line8: .globl line8");
+ k = j; f3 = f2; str_3 = str_2; /* TAG: line 8 */
+
+ asm ("main_return: .globl main_return");
+ k = j; f3 = f2; str_3 = str_2; /* TAG: main return */
+
+ asm ("end_of_sequence: .globl end_of_sequence");
+ return 0; /* TAG: main return */
+}
diff --git a/gdb/testsuite/gdb.reverse/map-to-same-line.exp b/gdb/testsuite/gdb.reverse/map-to-same-line.exp
new file mode 100644
index 00000000000..a01579c2a8d
--- /dev/null
+++ b/gdb/testsuite/gdb.reverse/map-to-same-line.exp
@@ -0,0 +1,153 @@
+# Copyright 2008-2023 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/ >.
+
+# When stepping (forwards or backwards), GDB should step over the entire line
+# and not just a particular entry in the line table. This test was added to
+# verify the find_line_range_start function properly sets the step range for a
+# line that consists of multiple statements, i.e. multiple entries in the line
+# table. This test creates a DWARF line table that contains two entries for
+# the same line to do the needed testing.
+
+load_lib dwarf.exp
+
+# This test can only be run on targets which support DWARF-2 and use gas.
+if {![dwarf2_support]} {
+ unsupported "dwarf2 support required for this test"
+ return 0
+}
+
+if [get_compiler_info] {
+ return -1
+}
+
+# The DWARF assembler requires the gcc compiler.
+if ![is_c_compiler_gcc] {
+ unsupported "gcc is required for this test"
+ return 0
+}
+
+# This test suitable only for process record-replay
+if ![supports_process_record] {
+ return
+}
+
+standard_testfile .c .S
+
+if { [prepare_for_testing "failed to prepare" ${testfile} ${srcfile}] } {
+ return -1
+}
+
+set asm_file [standard_output_file $srcfile2]
+Dwarf::assemble $asm_file {
+ global srcdir subdir srcfile
+ declare_labels integer_label L
+
+ # Find start address and length of program
+ lassign [function_range main [list ${srcdir}/${subdir}/$srcfile]] \
+ main_start main_len
+ set main_end "$main_start + $main_len"
+
+ cu {} {
+ compile_unit {
+ {language @DW_LANG_C}
+ {name map-to-same-line.c}
+ {stmt_list $L DW_FORM_sec_offset}
+ {low_pc 0 addr}
+ } {
+ subprogram {
+ {external 1 flag}
+ {name main}
+ {low_pc $main_start addr}
+ {high_pc $main_len DW_FORM_data4}
+ }
+ }
+ }
+
+ lines {version 2 default_is_stmt 1} L {
+ include_dir "${srcdir}/${subdir}"
+ file_name "$srcfile" 1
+
+ # Generate the line table program with distinct source lines being
+ # mapped to the same line entry. Line 1, 5 and 8 contain 1 statement
+ # each. Line 2 contains 2 statements. Line 3 contains 3 statements.
+ program {
+ DW_LNE_set_address $main_start
+ line [gdb_get_line_number "TAG: main prologue"]
+ DW_LNS_copy
+ DW_LNE_set_address line1
+ line [gdb_get_line_number "TAG: line 1" ]
+ DW_LNS_copy
+ DW_LNE_set_address line2
+ line [gdb_get_line_number "TAG: line 2" ]
+ DW_LNS_copy
+ DW_LNE_set_address line3
+ line [gdb_get_line_number "TAG: line 2" ]
+ DW_LNS_copy
+ DW_LNE_set_address line4
+ line [gdb_get_line_number "TAG: line 3" ]
+ DW_LNS_copy
+ DW_LNE_set_address line5
+ line [gdb_get_line_number "TAG: line 3" ]
+ DW_LNS_copy
+ DW_LNE_set_address line6
+ line [gdb_get_line_number "TAG: line 3" ]
+ DW_LNS_copy
+ DW_LNE_set_address line7
+ line [gdb_get_line_number "TAG: line 5" ]
+ DW_LNS_copy
+ DW_LNE_set_address line8
+ line [gdb_get_line_number "TAG: line 8" ]
+ DW_LNS_copy
+ DW_LNE_set_address main_return
+ line [gdb_get_line_number "TAG: main return"]
+ DW_LNS_copy
+ DW_LNE_set_address end_of_sequence
+ DW_LNE_end_sequence
+ }
+ }
+}
+
+if { [prepare_for_testing "failed to prepare" ${testfile} \
+ [list $srcfile $asm_file] {nodebug} ] } {
+ return -1
+}
+
+if ![runto_main] {
+ return -1
+}
+
+# Print the line table
+gdb_test_multiple "maint info line-table ${testfile}" "" {
+ -re "\r\n$decimal\[ \t\]+$decimal\[ \t\]+($hex)\[ \t\]+Y\[^\r\n\]*" {
+ lappend is_stmt $expect_out(1,string)
+ exp_continue
+ }
+ -re -wrap "" {
+ }
+}
+
+# Activate process record/replay
+gdb_test_no_output "record" "turn on process record"
+
+gdb_test "tbreak main_return" "Temporary breakpoint .*" "breakpoint at return"
+gdb_test "continue" "Temporary breakpoint .*" "run to end of main"
+gdb_test "display \$pc" ".*pc =.*" "display pc"
+
+# At this point, GDB has already recorded the execution up until the return
+# statement. Reverse-step and test if GDB transitions between lines in the
+# expected order. It should reverse-step across lines 8, 5, 3, 2 and 1.
+foreach line {8 5 3 2 1} {
+ gdb_test "reverse-step" ".*TAG: line $line.*" "reverse step to line $line"
+}
--
2.37.2