[Bug gdb/31211] New: [gdb] info checkpoints show incorrect info

["vries at gcc dot gnu.org" <sourceware-bugzilla@sourceware.org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=31211

            Bug ID: 31211
           Summary: [gdb] info checkpoints show incorrect info
           Product: gdb
           Version: HEAD
            Status: NEW
          Severity: normal
          Priority: P2
         Component: gdb
          Assignee: unassigned at sourceware dot org
          Reporter: vries at gcc dot gnu.org
  Target Milestone: ---

Consider test-case test.c:
...
$ cat test.c
#include <stdio.h>

int
main (void)
{
  printf ("1\n");
  printf ("2\n");
  printf ("3\n");
  printf ("4\n");
  printf ("5\n");
  printf ("6\n");
  printf ("7\n");
  printf ("8\n");
  printf ("9\n");
  printf ("10\n");

  return 0;
}
...

Compiled with:
...
$ gcc -g test.c
...

Let's look at the output of "info checkpoints":
...
$ gdb -q a.out
Reading symbols from a.out...
(gdb) start
Temporary breakpoint 1 at 0x40051b: file test.c, line 6.
Starting program: /data/vries/gdb/a.out 

Temporary breakpoint 1, main () at test.c:6
6         printf ("1\n");
(gdb) info checkpoints
No checkpoints.
...

OK, sofar so good.  Now let's add a checkpoint:
...
(gdb) checkpoint
checkpoint 1: fork returned pid 7886.
(gdb) info checkpoints 
* 0 process 7881 (main process) at 0x0
  1 process 7886 at 0x40051b, file test.c, line 6
...

The documentation says checkpoints, but what we really have is fork
child/parent, which are initially equal, so it's odd that they're not both
shown with "at 0x40051b, file test.c, line 6".

After switching to checkpoint 1, we have:
...
(gdb) restart 1
Switching to process 7886
#0  main () at test.c:6
6         printf ("1\n");
(gdb) info checkpoints 
  0 process 7881 (main process) at 0x40051b, file test.c, line 6
* 1 process 7886 at 0x40051b, file test.c, line 6
(gdb) 
...
OK, so now they're indeed equal.

Let's see what happens when we step to the next line:
...
(gdb) next
1
7         printf ("2\n");
(gdb) info checkpoints 
  0 process 7881 (main process) at 0x40051b, file test.c, line 6
* 1 process 7886 at 0x40051b, file test.c, line 6
(gdb) 
...
Hmm, the line number didn't change.

So, are we stuck at line 6?  Let's try switching forth and back:
...
(gdb) restart 0
Switching to process 7881
#0  main () at test.c:6
6         printf ("1\n");
(gdb) info checkpoints
* 0 process 7881 (main process) at 0x40051b, file test.c, line 6
  1 process 7886 at 0x400525, file test.c, line 7
(gdb) restart 1
Switching to process 7886
#0  main () at test.c:7
7         printf ("2\n");
(gdb) info checkpoints
  0 process 7881 (main process) at 0x40051b, file test.c, line 6
* 1 process 7886 at 0x400525, file test.c, line 7
(gdb) 
...
Now the line is updated to 7.

So, it seems info checkpoints show outdated info for the current fork.

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