[PATCH] printcmd.c (ui_printf): make internalvar string can be printf and eval when inferior cannot alloc memory

[Hui Zhu <teawater@gmail.com>]

Hi,

printf and eval commands call ui_printf to get the format string.
But I found that:
gdb
(gdb) p $a="pwd"
$1 = "pwd"
(gdb) p $a
$2 = "pwd"
(gdb) printf "%s\n", $a
evaluation of this expression requires the target program to be active
(gdb) eval "%s", $a
evaluation of this expression requires the target program to be active

This error is because we can alloc memory from inferior now.  But
ui_printf will call allocate_space_in_inferior to alloc inferior
memory.  This issue can reproduce in the inferior that cannot alloc
memory such as KGTP.

So I make a patch to handle the error from value_as_address.  If
value_as_address get error and this is a internalvar, call
value_contents to get the address of the val.

After this patch, gdb can always success with this commands.

Please help review the patch, it for the trunk and 7.3.

Thanks,
Hui

2011-07-20  Hui Zhu  <teawater@gmail.com>

	* printcmd.c (ui_printf): Add error handler for value_as_address.
---
 printcmd.c |   47 +++++++++++++++++++++++++++++++----------------
 1 file changed, 31 insertions(+), 16 deletions(-)

--- a/printcmd.c
+++ b/printcmd.c
@@ -2330,27 +2330,42 @@ ui_printf (char *arg, struct ui_file *st
 	      gdb_byte *str;
 	      CORE_ADDR tem;
 	      int j;
+	      volatile struct gdb_exception ex;

-	      tem = value_as_address (val_args[i]);
-
-	      /* This is a %s argument.  Find the length of the string.  */
-	      for (j = 0;; j++)
+	      TRY_CATCH (ex, RETURN_MASK_ERROR)
 		{
-		  gdb_byte c;
-
-		  QUIT;
-		  read_memory (tem + j, &c, 1);
-		  if (c == 0)
-		    break;
+		  tem = value_as_address (val_args[i]);
 		}
+	      if (ex.reason >= 0)
+		{
+		  /* This is a %s argument.  Find the length of the string.  */
+		  for (j = 0;; j++)
+		    {
+		      gdb_byte c;

-	      /* Copy the string contents into a string inside GDB.  */
-	      str = (gdb_byte *) alloca (j + 1);
-	      if (j != 0)
-		read_memory (tem, str, j);
-	      str[j] = 0;
+		      QUIT;
+		      read_memory (tem + j, &c, 1);
+		      if (c == 0)
+			break;
+		    }

-              fprintf_filtered (stream, current_substring, (char *) str);
+		  /* Copy the string contents into a string inside GDB.  */
+		  str = (gdb_byte *) alloca (j + 1);
+		  if (j != 0)
+		    read_memory (tem, str, j);
+		  str[j] = 0;
+
+		  fprintf_filtered (stream, current_substring, (char *) str);
+		}
+	      else
+		{
+		  if (VALUE_LVAL (val_args[i]) == lval_internalvar)
+		    fprintf_filtered (stream,
+				      current_substring,
+				      (char *) value_contents (val_args[i]));
+		  else
+		    error (_("%s"), ex.message);
+		}
 	    }
 	    break;
 	  case wide_string_arg: