[RFA] GDB/624 - tbreak commands not executed when breakpoint hit

[Joel Brobecker <brobecker at gnat dot com>]

As described in PR GDB/624:

Using the small program from gdb.base/commands.exp, the following copy
of a GDB sessions shows that commands associated to temporary
breakpoints are not executed when the breakpoint is hit:

        (gdb) tbreak factorial
        Breakpoint 1 at 0x8048582: file ./gdb.base/run.c, line 77.
        (gdb) commands
        Type commands for when breakpoint 1 is hit, one per line.
        End with a line saying just "end".
        >silent
        >printf "factorial command-list executed\n"
        >cont
        >end
        (gdb) run 1
        Starting program: [...]/gdb.base/commands 1
        (gdb)

The backtrace confirms that the program executed up to the factorial
breakpoint, and then stopped.

        (gdb) bt
        #0  factorial (value=1) at ./gdb.base/run.c:77
        #1  0x0804855e in main (argc=2, argv=0xbffffa34, envp=0xbffffa40)
            at ./gdb.base/run.c:57
        #2  0x4005514f in __libc_start_main () from /lib/libc.so.6
        (gdb) p /x $pc
        $1 = 0x8048582        <<<--- $pc is equal to bp #1 address

The expected output after the run command was:

        (gdb) run 1
        Starting program: [...]/gdb.base/commands 1
        factorial command-list executed
        1

        Program exited normally.
        (gdb)

The problem is that the breakpoint is deleted very early in the inferior
stop handling, so the rest of the code does not have a chance to see
that there was a temporary breakpoint there with a commands list to
execute. To fix this, it is necessary to delay a bit the deletion of
this breakpoint.

This is what the attached patch does. There is a small side-effect,
which I think should be ok, is that the after the temporary breakpoint
is hit, there is a small period during which the breakpoint is still
visible when doing ``info break''. The status report is disabled, and to
be deleted at the next stop.

I also attached an extra test in gdb.base/commands.exp.

No new regression introduced on x86-linux.

Ok to apply?

2002-07-31  Joel Brobecker  <brobecker@gnat.com>

        * breakpoint.c (breakpoint_auto_delete): Do not delete temporary
        breakpoints to which a list of commands is attached. Mark them
        for deletion at the next stop instead. Also disable them to avoid
        hitting these breakpoints again.
        Move the part that deletes the to-be-deleted breakpoints before
        the part that deletes the temporary breakpoints, to avoid immediately
        deleting the temporary breakpoints that we just marked for deletion.

2002-07-31  Joel Brobecker  <brobecker@gnat.com>

        * gdb.base/commands.exp (temporary_breakpoint_commands): New test.

Thanks,
-- 
Joel

Attachment: tbreak_commands.diff
Description: Text document