[binutils-gdb] [gdb/breakpoint] Fix stepping past non-stmt line-table entries
Tom de Vries
vries@sourceware.org
Fri Jan 29 12:36:55 GMT 2021
https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=ebde6f2ddc987e7e2d5a218ee8cf0126ec189424
commit ebde6f2ddc987e7e2d5a218ee8cf0126ec189424
Author: Tom de Vries <tdevries@suse.de>
Date: Fri Jan 29 13:36:52 2021 +0100
[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.
Diff:
---
gdb/ChangeLog | 7 ++
gdb/infrun.c | 33 ++++--
gdb/testsuite/ChangeLog | 6 +
.../gdb.dwarf2/dw2-step-out-of-function-no-stmt.c | 44 +++++++
.../dw2-step-out-of-function-no-stmt.exp | 126 +++++++++++++++++++++
5 files changed, 208 insertions(+), 8 deletions(-)
diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 1de9d30f051..9d928b01eba 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,10 @@
+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.
+
2021-01-28 Andrew Burgess <andrew.burgess@embecosm.com>
* thread.c (thr_try_catch_cmd): Replace swith_to_thread with an
diff --git a/gdb/infrun.c b/gdb/infrun.c
index 3f143971707..e070eff33d7 100644
--- a/gdb/infrun.c
+++ b/gdb/infrun.c
@@ -7000,27 +7000,44 @@ process_event_stop_test (struct execution_control_state *ecs)
&& (ecs->event_thread->current_line != stop_pc_sal.line
|| ecs->event_thread->current_symtab != stop_pc_sal.symtab))
{
+ /* We are at a different line. */
+
if (stop_pc_sal.is_stmt)
{
- /* We are at the start of a different line. So stop. Note that
- we don't stop if we step into the middle of a different line.
- That is said to make things like for (;;) statements work
- better. */
+ /* We are at the start of a statement.
+
+ So stop. Note that we don't stop if we step into the middle of a
+ statement. That is said to make things like for (;;) statements
+ work better. */
infrun_debug_printf ("stepped to a different line");
end_stepping_range (ecs);
return;
}
else if (frame_id_eq (get_frame_id (get_current_frame ()),
- ecs->event_thread->control.step_frame_id))
+ ecs->event_thread->control.step_frame_id))
{
- /* We are at the start of a different line, however, this line is
- not marked as a statement, and we have not changed frame. We
- ignore this line table entry, and continue stepping forward,
+ /* We are not at the start of a statement, and we have not changed
+ frame.
+
+ We ignore this line table entry, and continue stepping forward,
looking for a better place to stop. */
refresh_step_info = false;
infrun_debug_printf ("stepped to a different line, but "
"it's not the start of a statement");
}
+ else
+ {
+ /* We are not the start of a statement, and we have changed frame.
+
+ We ignore this line table entry, and continue stepping forward,
+ looking for a better place to stop. Keep refresh_step_info at
+ true to note that the frame has changed, but ignore the line
+ number to make sure we don't ignore a subsequent entry with the
+ same line number. */
+ stop_pc_sal.line = 0;
+ infrun_debug_printf ("stepped to a different frame, but "
+ "it's not the start of a statement");
+ }
}
/* We aren't done stepping.
diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index 842f9a5d7b7..36ba5d01c40 100644
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,3 +1,9 @@
+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.
+
2021-01-29 Tom de Vries <tdevries@suse.de>
* gdb.opt/solib-intra-step.exp: Remove state tracking logic.
diff --git a/gdb/testsuite/gdb.dwarf2/dw2-step-out-of-function-no-stmt.c b/gdb/testsuite/gdb.dwarf2/dw2-step-out-of-function-no-stmt.c
new file mode 100644
index 00000000000..a8184f0c1bb
--- /dev/null
+++ b/gdb/testsuite/gdb.dwarf2/dw2-step-out-of-function-no-stmt.c
@@ -0,0 +1,44 @@
+/*
+ Copyright 2021 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/>. */
+
+void
+foo (int x)
+{
+
+}
+
+void
+bar (void)
+{
+ asm ("bar_label: .globl bar_label");
+}
+
+int
+main (void)
+{
+ asm ("main_label: .globl main_label");
+
+ bar ();
+
+ asm ("main_label_2: .globl main_label_2");
+
+ foo (10);
+
+ asm ("main_label_3: .globl main_label_3");
+
+ return 0;
+}
+
diff --git a/gdb/testsuite/gdb.dwarf2/dw2-step-out-of-function-no-stmt.exp b/gdb/testsuite/gdb.dwarf2/dw2-step-out-of-function-no-stmt.exp
new file mode 100644
index 00000000000..9249eb590f7
--- /dev/null
+++ b/gdb/testsuite/gdb.dwarf2/dw2-step-out-of-function-no-stmt.exp
@@ -0,0 +1,126 @@
+# Copyright 2021 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/>.
+
+# Check whether stepping out of a function works, in case:
+# - the first insn after the call has an is-stmt=no entry
+# - the next insn has an is-stmt=yes entry, for the same line number
+#
+# This sort of thing can occur in optimized code, f.i. here a slightly more
+# elaborate case with another is-stmt=no entry (the one with line number 12)
+# inbetween:
+# INDEX LINE ADDRESS IS-STMT
+# 12 13 0x00000000004003ed
+# 13 12 0x00000000004003f2
+# 14 13 0x00000000004003f4 Y
+
+load_lib dwarf.exp
+
+# This test can only be run on targets which support DWARF-2 and use gas.
+if {![dwarf2_support]} {
+ verbose "Skipping $gdb_test_file_name."
+ return 0
+}
+
+# The .c files use __attribute__.
+if [get_compiler_info] {
+ return -1
+}
+if !$gcc_compiled {
+ verbose "Skipping $gdb_test_file_name."
+ return 0
+}
+
+standard_testfile .c -dw.S
+
+set asm_file [standard_output_file $srcfile2]
+Dwarf::assemble $asm_file {
+ declare_labels Llines
+ global srcdir subdir srcfile
+
+ lassign [function_range main [list ${srcdir}/${subdir}/$srcfile]] \
+ main_start main_len
+ set main_end "$main_start + $main_len"
+
+ lassign [function_range main [list ${srcdir}/${subdir}/$srcfile]] \
+ bar_start bar_len
+ set bar_end "$bar_start + $bar_len"
+
+ cu {} {
+ compile_unit {
+ {language @DW_LANG_C}
+ {name $srcfile}
+ {stmt_list $Llines DW_FORM_sec_offset}
+ } {
+ subprogram {
+ {external 1 flag}
+ {MACRO_AT_func {main}}
+ }
+ subprogram {
+ {external 1 flag}
+ {MACRO_AT_func {bar}}
+ }
+ }
+ }
+
+ lines {version 2} Llines {
+ include_dir "${srcdir}/${subdir}"
+ file_name "$srcfile" 1
+
+ program {
+ {DW_LNE_set_address bar_label}
+ {line 26}
+ {DW_LNS_copy}
+
+ {DW_LNE_set_address $bar_end}
+ {DW_LNE_end_sequence}
+
+ {DW_LNE_set_address main_label}
+ {line 32}
+ {DW_LNS_copy}
+
+ {DW_LNE_set_address main_label_2}
+ {line 36}
+ {DW_LNS_negate_stmt}
+ {DW_LNS_copy}
+ {DW_LNS_negate_stmt}
+
+ {DW_LNE_set_address main_label_3}
+ {line 36}
+ {DW_LNS_copy}
+
+ {DW_LNE_set_address $main_end}
+ {DW_LNE_end_sequence}
+ }
+ }
+}
+
+if { [prepare_for_testing "failed to prepare" ${testfile} \
+ [list $srcfile $asm_file] {nodebug}] } {
+ return -1
+}
+
+if ![runto_main] {
+ return -1
+}
+
+# Step into bar.
+gdb_breakpoint "bar"
+gdb_continue_to_breakpoint "bar"
+
+# Step out of bar.
+gdb_test "step" [multi_line \
+ "main \\(\\) at \[^\r\n\]*$srcfile:36" \
+ "36\t\[^\r\n\]*"]
+
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