[lldb-dev] [PATCH] Fixing a crashing bug in multiword commands

[Greg Clayton]

Committed revision 108958.

On Jul 20, 2010, at 1:44 PM, William Lynch wrote:

> Hi everyone,
> 
> Currently, this is the output from a LLDB session:
> 
> [3:21pm][wlynch at orange bin] ./lldb 
> (lldb) process
> terminate called after throwing an instance of 'std::logic_error'
>   what():  basic_string::_S_construct NULL not valid
> 
> If the attached patch is applied, the following is the LLDB session:
> 
> [3:25pm][wlynch at orange bin] ./lldb 
> (lldb) process
> The following subcommands are supported:
> 
>     attach    -- Attaches to a process.
>     continue  -- Continues execution all threads in the current process.
>     detach    -- Detaches from the current process being debugged.
>     interrupt -- Interrupts the current process being debugged.
>     kill      -- Terminates the current process being debugged.
>     launch    -- Launches the executable in the debugger.
>     signal    -- Sends a UNIX signal to the current process being debugged.
>     status    -- Shows the current status and location of executing process.
> 
> For more help on any particular subcommand, type 'help <command> <subcommand>'.
> 
> Here's some notes on what's going on:
> 
> So, "process" is a multiword command object. That is, it uses CommandObjectMultiword to choose between a set of possible classes. In CommandObjectMultiword, a map is created to search for the desired subcommand. If null is searched for in that map, an uncaught exception is thrown by the standard library. Basically, it calls std::string(NULL). 
> 
> The fix for this is to make sure that when we look for the next subcommand, to verify that one does in fact exist. 
> 
> And here's the patch:
> 
> Index: source/Commands/CommandObjectMultiword.cpp
> ===================================================================
> --- source/Commands/CommandObjectMultiword.cpp	(revision 108841)
> +++ source/Commands/CommandObjectMultiword.cpp	(working copy)
> @@ -290,13 +290,12 @@
>  const char *
>  CommandObjectMultiword::GetRepeatCommand (Args &current_command_args, uint32_t index)
>  {
> -    if (current_command_args.GetArgumentCount() == 0)
> -        return NULL;
>      index++;
> +    if (current_command_args.GetArgumentCount() <= index)
> +        return NULL;
>      CommandObject *sub_command_object = GetSubcommandObject (current_command_args.GetArgumentAtIndex(index));
>      if (sub_command_object == NULL)
>          return NULL;
> -    else 
>      return sub_command_object->GetRepeatCommand(current_command_args, index);
>  }
> 
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