Re: [PATCH] alpha: Use ssize_t to allocate space on stack

[Jan Kratochvil <jan dot kratochvil at redhat dot com>]

On Tue, 25 Sep 2012 17:37:20 +0200, Siddhesh Poyarekar wrote:
> --- gdb/alpha-tdep.c	25 Sep 2012 12:48:52 -0000	1.212
> +++ gdb/alpha-tdep.c	25 Sep 2012 15:21:46 -0000
> @@ -299,18 +299,18 @@
>  {
>    enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
>    int i;
> -  int accumulate_size = struct_return ? 8 : 0;
> +  ssize_t accumulate_size = struct_return ? 8 : 0;
>    struct alpha_arg
>      {
>        const gdb_byte *contents;
> -      int len;
> -      int offset;
> +      ssize_t len;
> +      ssize_t offset;
>      };
>    struct alpha_arg *alpha_args
>      = (struct alpha_arg *) alloca (nargs * sizeof (struct alpha_arg));
>    struct alpha_arg *m_arg;
>    gdb_byte arg_reg_buffer[ALPHA_REGISTER_SIZE * ALPHA_NUM_ARG_REGS];
> -  int required_arg_regs;
> +  ssize_t required_arg_regs;
>    CORE_ADDR func_addr = find_function_addr (function, NULL);
>  
>    /* The ABI places the address of the called function in T12.  */

At line 409 is also code:
       m_arg->len = TYPE_LENGTH (arg_type);

This is unsafe with extended TYPE_LENGTH width, because LONGEST > ssize_t.


> @@ -414,6 +414,13 @@
>      accumulate_size = 0;
>    else
>      accumulate_size -= sizeof(arg_reg_buffer);
> +
> +  /* Check for underflow.  */
> +  if (sp - accumulate_size > sp)
> +    error (_("Insufficient memory in GDB host for arguments, "
> +	     "need %s bytes, but less than %s bytes available."),
> +	   plongest (accumulate_size), plongest (CORE_ADDR_MAX - sp));
> +
>    sp -= accumulate_size;
>  
>    /* Keep sp aligned to a multiple of 16 as the ABI requires.  */
> @@ -423,8 +430,8 @@
>    for (i = nargs; m_arg--, --i >= 0;)
>      {
>        const gdb_byte *contents = m_arg->contents;
> -      int offset = m_arg->offset;
> -      int len = m_arg->len;
> +      ssize_t offset = m_arg->offset;
> +      ssize_t len = m_arg->len;
>  
>        /* Copy the bytes destined for registers into arg_reg_buffer.  */
>        if (offset < sizeof(arg_reg_buffer))
> @@ -436,7 +443,7 @@
>  	    }
>  	  else
>  	    {
> -	      int tlen = sizeof(arg_reg_buffer) - offset;
> +	      ssize_t tlen = sizeof(arg_reg_buffer) - offset;

FYI this is not needed; but the code may be easier keeping it as you wrote it.


>  	      memcpy (arg_reg_buffer + offset, contents, tlen);
>  	      offset += tlen;
>  	      contents += tlen;


Thanks,
Jan