[patch] fix out-of-bounds error

["Grégoire Sutre" <gregoire.sutre@gmail.com>]

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I get the following warning on Debian GNU/Linux when compiling
with -O2.  This is with GCC 4.6.3.

$ CFLAGS='-O2' ./configure && make
...
gdb/cstub.c: In function 'grub_gdb_trap':
gdb/cstub.c:83:21: error: array subscript is above array bounds 
[-Werror=array-bounds]
cc1: all warnings being treated as errors
make[3]: *** [gdb/gdb_module-cstub.o] Error 1
make[3]: Leaving directory `/tmp/GRUB/trunk/grub-core'

Afaics, the out-of-bounds error is real, and the attached patch
fixes it.

Grégoire

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=== modified file 'grub-core/gdb/cstub.c'
--- grub-core/gdb/cstub.c	2012-02-26 18:10:52 +0000
+++ grub-core/gdb/cstub.c	2012-03-18 13:46:51 +0000
@@ -57,27 +57,27 @@ grub_gdb_getpacket (void)
 
   while (1)
     {
       /* Wait around for the start character, ignore all other
          characters.  */
       while ((ch = grub_serial_port_fetch (grub_gdb_port)) != '$');
 
     retry:
       checksum = 0;
       xmitcsum = -1;
       count = 0;
 
       /* Now read until a # or end of buffer is found.  */
-      while (count < GRUB_GDB_COMBUF_SIZE)
+      while (count < GRUB_GDB_COMBUF_SIZE - 1)
 	{
 	  do
 	    ch = grub_serial_port_fetch (grub_gdb_port);
 	  while (ch < 0);
 	  if (ch == '$')
 	    goto retry;
 	  if (ch == '#')
 	    break;
 	  checksum += ch;
 	  buffer[count] = ch;
 	  count = count + 1;
 	}
       buffer[count] = 0;