Re: [PATCH, gdbsim] Avoid silly crash when no binary is loaded

[Pedro Alves <palves at redhat dot com>]

On 06/18/2013 09:49 PM, Luis Machado wrote:
> Hi,
> 
> This patch prevents the long-standing crash scenario where we start 
> gdbsim and "run" without any binaries. Warnings are issued, but those 
> don't prevent the simulator from proceeding with garbage data.

Which sim and backtrace?  I suspect this to be sim/arch dependent.

> 
> Replacing those warnings with error calls seems to be the most 
> appropriate here.

Well, the code seems to have been written like that for a reason.

Real boards can be powered on with no real program in memory
too...

>    if (exec_file == 0 || exec_bfd == 0)
> -    warning (_("No executable file specified."));
> +    error (_("No executable file specified."));
>    if (!sim_data->program_loaded)
> -    warning (_("No program loaded."));
> +    error (_("No program loaded."));
>

There's code just below that does:

>    if (remote_debug)
>      printf_filtered ("gdbsim_create_inferior: exec_file \"%s\", args \"%s\"\n",
...
>  if (exec_file != NULL)
>    {
>      len = strlen (exec_file) + 1 + strlen (args) + 1 + /*slop */ 10;
>      arg_buf = (char *) alloca (len);
>      arg_buf[0] = '\0';
>      strcat (arg_buf, exec_file);
>      strcat (arg_buf, " ");
>      strcat (arg_buf, args);
>      argv = gdb_buildargv (arg_buf);
>      make_cleanup_freeargv (argv);
>    }
>  else
>    argv = NULL;

So if we error out, then these NULL checks are now dead.

And e.g., the bfin sim, at sim/bfin/interp.c:sim_create_inferior
allows NULL exec_bfd:

SIM_RC
sim_create_inferior (SIM_DESC sd, struct bfd *abfd,
		     char **argv, char **env)
{
  SIM_CPU *cpu = STATE_CPU (sd, 0);
  SIM_ADDR addr;

  /* Set the PC.  */
  if (abfd != NULL)
    addr = bfd_get_start_address (abfd);
  else
    addr = 0;
  sim_pc_set (cpu, addr);

-- 
Pedro Alves