ebde6f2ddc
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.
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