[RFA] GDB/622 - clear current breakpoint in commands causes trouble

[Joel Brobecker <brobecker at gnat dot com>]

As described in PR GDB/622:

Using the program in the gdb.base/commands.exp testcase, the following
session shows that clearing the current breakpoint inside its commands
list causes a memory-corruption problem:

       (gdb) b 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"
       >clear factorial
       >cont
       >end
       (gdb) run 1
       Starting program: [...]/gdb.base/commands 1
       factorial command-list executed
       warning: Invalid control type in command structure.      <<<--- (1)
       (gdb)

(1) shows that the command-list becomes corrupted, and as a consequence,
the execution is not resumed.  Instead, the expected output from the run
command is:

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

       Program exited normally.
       (gdb)

The fix consists into executing a copy of the commands list, to protect
this execution from using a list that has been freed. The attached patch
introduces no regression. A new test has also been added to commands.exp.

Ok to apply?

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

        * cli/cli-scripts.c (copy_command_lines): New function.
        (make_cleanup_free_command_lines): Make this function non static.

        * defs.h (copy_command_lines): Add definition.
        (make_cleanup_free_command_lines): Add definition.

        * breakpoint.c (bpstat_do_actions): Execute a temporary copy of
        the command-list associated to each breakpoint hit, in order to
        avoid accessing a dangling pointer, in case one of the commands
        in the list causes the breakpoint to be deleted.

Thanks,
-- 
Joel

Attachment: clear_in_commands.diff
Description: Text document