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[gdb/breakpoint] Fix stepping past non-stmt line-table entries
Consider the test-case small.c:
...
$ cat -n small.c
1 __attribute__ ((noinline, noclone))
2 int foo (char *c)
3 {
4 asm volatile ("" : : "r" (c) : "memory");
5 return 1;
6 }
7
8 int main ()
9 {
10 char tpl1[20] = "/tmp/test.XXX";
11 char tpl2[20] = "/tmp/test.XXX";
12 int fd1 = foo (tpl1);
13 int fd2 = foo (tpl2);
14 if (fd1 == -1) {
15 return 1;
16 }
17
18 return 0;
19 }
...
Compiled with gcc-8 and optimization:
...
$ gcc-8 -O2 -g small.c
...
We step through the calls to foo, but fail to visit line 13:
...
12 int fd1 = foo (tpl1);
(gdb) step
foo (c=c@entry=0x7fffffffdea0 "/tmp/test.XXX") at small.c:5
5 return 1;
(gdb) step
foo (c=c@entry=0x7fffffffdec0 "/tmp/test.XXX") at small.c:5
5 return 1;
(gdb) step
main () at small.c:14
14 if (fd1 == -1) {
(gdb)
...
This is caused by the following. The calls to foo are implemented by these
insns:
....
4003df: 0f 29 04 24 movaps %xmm0,(%rsp)
4003e3: 0f 29 44 24 20 movaps %xmm0,0x20(%rsp)
4003e8: e8 03 01 00 00 callq 4004f0 <foo>
4003ed: 48 8d 7c 24 20 lea 0x20(%rsp),%rdi
4003f2: 89 c2 mov %eax,%edx
4003f4: e8 f7 00 00 00 callq 4004f0 <foo>
4003f9: 31 c0 xor %eax,%eax
...
with corresponding line table entries:
...
INDEX LINE ADDRESS IS-STMT
8 12 0x00000000004003df Y
9 10 0x00000000004003df
10 11 0x00000000004003e3
11 12 0x00000000004003e8
12 13 0x00000000004003ed
13 12 0x00000000004003f2
14 13 0x00000000004003f4 Y
15 13 0x00000000004003f4
16 14 0x00000000004003f9 Y
17 14 0x00000000004003f9
...
Once we step out of the call to foo at 4003e8, we land at 4003ed, and gdb
enters process_event_stop_test to figure out what to do.
That entry has is-stmt=n, so it's not the start of a line, so we don't stop
there. However, we do update ecs->event_thread->current_line to line 13,
because the frame has changed (because we stepped out of the function).
Next we land at 4003f2. Again the entry has is-stmt=n, so it's not the start
of a line, so we don't stop there. However, because the frame hasn't changed,
we don't update update ecs->event_thread->current_line, so it stays 13.
Next we land at 4003f4. Now is-stmt=y, so it's the start of a line, and we'd
like to stop here.
But we don't stop because this test fails:
...
if ((ecs->event_thread->suspend.stop_pc == stop_pc_sal.pc)
&& (ecs->event_thread->current_line != stop_pc_sal.line
|| ecs->event_thread->current_symtab != stop_pc_sal.symtab))
{
...
because ecs->event_thread->current_line == 13 and stop_pc_sal.line == 13.
Fix this by resetting ecs->event_thread->current_line to 0 if is-stmt=n and
the frame has changed, such that we have:
...
12 int fd1 = foo (tpl1);
(gdb) step
foo (c=c@entry=0x7fffffffdbc0 "/tmp/test.XXX") at small.c:5
5 return 1;
(gdb) step
main () at small.c:13
13 int fd2 = foo (tpl2);
(gdb)
...
Tested on x86_64-linux, with gcc-7 and gcc-8.
gdb/ChangeLog:
2021-01-29 Tom de Vries <tdevries@suse.de>
PR breakpoints/26063
* infrun.c (process_event_stop_test): Reset
ecs->event_thread->current_line to 0 if is-stmt=n and frame has
changed.
gdb/testsuite/ChangeLog:
2021-01-29 Tom de Vries <tdevries@suse.de>
PR breakpoints/26063
* gdb.dwarf2/dw2-step-out-of-function-no-stmt.c: New test.
* gdb.dwarf2/dw2-step-out-of-function-no-stmt.exp: New file.
This commit is contained in:
Tom de Vries
parent
620ec3caae
commit
ebde6f2ddc
@ -1,3 +1,10 @@
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2021-01-29 Tom de Vries <tdevries@suse.de>
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PR breakpoints/26063
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* infrun.c (process_event_stop_test): Reset
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ecs->event_thread->current_line to 0 if is-stmt=n and frame has
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changed.
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2021-01-28 Andrew Burgess <andrew.burgess@embecosm.com>
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* thread.c (thr_try_catch_cmd): Replace swith_to_thread with an
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33
gdb/infrun.c
33
gdb/infrun.c
@ -7000,27 +7000,44 @@ process_event_stop_test (struct execution_control_state *ecs)
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&& (ecs->event_thread->current_line != stop_pc_sal.line
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|| ecs->event_thread->current_symtab != stop_pc_sal.symtab))
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{
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/* We are at a different line. */
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if (stop_pc_sal.is_stmt)
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{
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/* We are at the start of a different line. So stop. Note that
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we don't stop if we step into the middle of a different line.
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That is said to make things like for (;;) statements work
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better. */
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/* We are at the start of a statement.
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So stop. Note that we don't stop if we step into the middle of a
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statement. That is said to make things like for (;;) statements
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work better. */
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infrun_debug_printf ("stepped to a different line");
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end_stepping_range (ecs);
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return;
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}
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else if (frame_id_eq (get_frame_id (get_current_frame ()),
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ecs->event_thread->control.step_frame_id))
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ecs->event_thread->control.step_frame_id))
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{
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/* We are at the start of a different line, however, this line is
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not marked as a statement, and we have not changed frame. We
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ignore this line table entry, and continue stepping forward,
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/* We are not at the start of a statement, and we have not changed
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frame.
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We ignore this line table entry, and continue stepping forward,
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looking for a better place to stop. */
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refresh_step_info = false;
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infrun_debug_printf ("stepped to a different line, but "
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"it's not the start of a statement");
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}
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else
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{
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/* We are not the start of a statement, and we have changed frame.
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We ignore this line table entry, and continue stepping forward,
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looking for a better place to stop. Keep refresh_step_info at
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true to note that the frame has changed, but ignore the line
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number to make sure we don't ignore a subsequent entry with the
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same line number. */
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stop_pc_sal.line = 0;
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infrun_debug_printf ("stepped to a different frame, but "
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"it's not the start of a statement");
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}
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}
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/* We aren't done stepping.
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@ -1,3 +1,9 @@
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2021-01-29 Tom de Vries <tdevries@suse.de>
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PR breakpoints/26063
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* gdb.dwarf2/dw2-step-out-of-function-no-stmt.c: New test.
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* gdb.dwarf2/dw2-step-out-of-function-no-stmt.exp: New file.
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2021-01-29 Tom de Vries <tdevries@suse.de>
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* gdb.opt/solib-intra-step.exp: Remove state tracking logic.
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44
gdb/testsuite/gdb.dwarf2/dw2-step-out-of-function-no-stmt.c
Normal file
44
gdb/testsuite/gdb.dwarf2/dw2-step-out-of-function-no-stmt.c
Normal file
@ -0,0 +1,44 @@
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/*
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Copyright 2021 Free Software Foundation, Inc.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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(at your option) any later version.
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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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void
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foo (int x)
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{
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}
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void
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bar (void)
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{
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asm ("bar_label: .globl bar_label");
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}
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int
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main (void)
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{
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asm ("main_label: .globl main_label");
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bar ();
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asm ("main_label_2: .globl main_label_2");
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foo (10);
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asm ("main_label_3: .globl main_label_3");
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return 0;
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}
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126
gdb/testsuite/gdb.dwarf2/dw2-step-out-of-function-no-stmt.exp
Normal file
126
gdb/testsuite/gdb.dwarf2/dw2-step-out-of-function-no-stmt.exp
Normal file
@ -0,0 +1,126 @@
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# Copyright 2021 Free Software Foundation, Inc.
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# This program is free software; you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation; either version 3 of the License, or
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# (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with this program. If not, see <http://www.gnu.org/licenses/>.
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# Check whether stepping out of a function works, in case:
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# - the first insn after the call has an is-stmt=no entry
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# - the next insn has an is-stmt=yes entry, for the same line number
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#
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# This sort of thing can occur in optimized code, f.i. here a slightly more
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# elaborate case with another is-stmt=no entry (the one with line number 12)
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# inbetween:
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# INDEX LINE ADDRESS IS-STMT
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# 12 13 0x00000000004003ed
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# 13 12 0x00000000004003f2
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# 14 13 0x00000000004003f4 Y
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load_lib dwarf.exp
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# This test can only be run on targets which support DWARF-2 and use gas.
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if {![dwarf2_support]} {
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verbose "Skipping $gdb_test_file_name."
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return 0
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}
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# The .c files use __attribute__.
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if [get_compiler_info] {
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return -1
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}
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if !$gcc_compiled {
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verbose "Skipping $gdb_test_file_name."
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return 0
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}
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standard_testfile .c -dw.S
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set asm_file [standard_output_file $srcfile2]
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Dwarf::assemble $asm_file {
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declare_labels Llines
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global srcdir subdir srcfile
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lassign [function_range main [list ${srcdir}/${subdir}/$srcfile]] \
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main_start main_len
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set main_end "$main_start + $main_len"
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lassign [function_range main [list ${srcdir}/${subdir}/$srcfile]] \
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bar_start bar_len
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set bar_end "$bar_start + $bar_len"
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cu {} {
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compile_unit {
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{language @DW_LANG_C}
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{name $srcfile}
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{stmt_list $Llines DW_FORM_sec_offset}
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} {
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subprogram {
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{external 1 flag}
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{MACRO_AT_func {main}}
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}
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subprogram {
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{external 1 flag}
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{MACRO_AT_func {bar}}
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}
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}
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}
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lines {version 2} Llines {
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include_dir "${srcdir}/${subdir}"
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file_name "$srcfile" 1
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program {
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{DW_LNE_set_address bar_label}
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{line 26}
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{DW_LNS_copy}
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{DW_LNE_set_address $bar_end}
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{DW_LNE_end_sequence}
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{DW_LNE_set_address main_label}
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{line 32}
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{DW_LNS_copy}
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{DW_LNE_set_address main_label_2}
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{line 36}
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{DW_LNS_negate_stmt}
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{DW_LNS_copy}
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{DW_LNS_negate_stmt}
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{DW_LNE_set_address main_label_3}
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{line 36}
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{DW_LNS_copy}
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{DW_LNE_set_address $main_end}
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{DW_LNE_end_sequence}
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}
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}
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}
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if { [prepare_for_testing "failed to prepare" ${testfile} \
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[list $srcfile $asm_file] {nodebug}] } {
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return -1
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}
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if ![runto_main] {
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return -1
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}
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# Step into bar.
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gdb_breakpoint "bar"
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gdb_continue_to_breakpoint "bar"
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# Step out of bar.
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gdb_test "step" [multi_line \
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"main \\(\\) at \[^\r\n\]*$srcfile:36" \
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"36\t\[^\r\n\]*"]
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