[PATCH] Catch errors in value_get_print_value

[Nick Roberts <nickrob@snap.net.nz>]

Currently when common_val_print throws an error from install_new_value it gets
caught in mi_execute_command and prints an MI error (^error,...)  without
cleaning up.  This patch catches the error in value_get_print_value so that GDB
can proceed normally.  It could be adapted to output something like
"<error_reading_variable>" but I think the empty string works better.

To see what currently happens, compile:

#include <stdlib.h>

typedef struct {
  float a;
  float b;
} substruct;

struct substruct1 {
  float a1;
  substruct b1;
};

main () {
  
struct substruct1 *abc4 = NULL;
 int i = 1;
}

-------------------
and run under GDB as follows:


~"Using host libthread_db library \"/lib/libthread_db.so.1\".\n"
(gdb)
start
&"start\n"
Breakpoint 1 at 0x8048365: file temp4.c, line 15.
Starting program: /home/nickrob/temp4
main () at temp4.c:15
15      struct substruct1 *abc4 = NULL;
^done
(gdb)
n
&"n\n"
16       int i = 1;
^done
(gdb)
-var-create - * abc4
^done,name="var1",numchild="2",type="struct substruct1 *"
(gdb)
-var-list-children --all-values var1
&"Cannot access memory at address 0x4\n"
^error,msg="Cannot access memory at address 0x4"
(gdb)
-var-list-children --all-values var1
&&"Duplicate variable object name\n"
^error,msg="Duplicate variable object name"
(gdb)


-- 
Nick                                           http://www.inet.net.nz/~nickrob


2007-02-02  Nick Roberts  <nickrob@snap.net.nz>

	* varobj.c (value_get_print_value): Catch errors from
	common_val_print.


  
*** varobj.c	02 Feb 2007 09:32:33 +1300	1.82
--- varobj.c	02 Feb 2007 09:48:59 +1300	
*************** value_get_print_value (struct value *val
*** 1702,1707 ****
--- 1702,1708 ----
    struct ui_file *stb;
    struct cleanup *old_chain;
    char *thevalue;
+   struct gdb_exception except;
  
    if (value == NULL)
      return NULL;
*************** value_get_print_value (struct value *val
*** 1709,1715 ****
    stb = mem_fileopen ();
    old_chain = make_cleanup_ui_file_delete (stb);
  
!   common_val_print (value, stb, format_code[(int) format], 1, 0, 0);
    thevalue = ui_file_xstrdup (stb, &dummy);
  
    do_cleanups (old_chain);
--- 1710,1720 ----
    stb = mem_fileopen ();
    old_chain = make_cleanup_ui_file_delete (stb);
  
!   TRY_CATCH (except, RETURN_MASK_ERROR)
!     {
!       common_val_print (value, stb, format_code[(int) format], 1, 0, 0);
!     }
! 
    thevalue = ui_file_xstrdup (stb, &dummy);
  
    do_cleanups (old_chain);