Re: Ping! [PATCH]: Tracking and reporting uninitialized variables

[Caroline Tice <ctice@apple.com>]

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Okay,  I agree with your suggestions and have made the changes.  The
modified patch is attached.  Is this okay to commit?

-- Caroline Tice
ctice@apple.com



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Index: gdb/c-valprint.c
===================================================================
RCS file: /cvs/src/src/gdb/c-valprint.c,v
retrieving revision 1.42
diff -c -3 -p -r1.42 c-valprint.c
*** gdb/c-valprint.c	26 Jan 2007 20:54:16 -0000	1.42
--- gdb/c-valprint.c	17 May 2007 16:59:06 -0000
*************** c_value_print (struct value *val, struct
*** 556,561 ****
--- 556,564 ----
  	}
      }
  
+   if (!value_initialized (val))
+     fprintf_filtered (stream, " [uninitialized] ");
+ 
    if (objectprint && (TYPE_CODE (type) == TYPE_CODE_CLASS))
      {
        /* Attempt to determine real type of object */
Index: gdb/dwarf2expr.c
===================================================================
RCS file: /cvs/src/src/gdb/dwarf2expr.c,v
retrieving revision 1.20
diff -c -3 -p -r1.20 dwarf2expr.c
*** gdb/dwarf2expr.c	27 Apr 2007 22:34:56 -0000	1.20
--- gdb/dwarf2expr.c	17 May 2007 16:59:08 -0000
*************** execute_stack_op (struct dwarf_expr_cont
*** 284,289 ****
--- 284,290 ----
  		  gdb_byte *op_ptr, gdb_byte *op_end)
  {
    ctx->in_reg = 0;
+   ctx->initialized = 1;  /* Default is initialized.  */
  
    while (op_ptr < op_end)
      {
*************** execute_stack_op (struct dwarf_expr_cont
*** 410,416 ****
  	case DW_OP_reg29:
  	case DW_OP_reg30:
  	case DW_OP_reg31:
! 	  if (op_ptr != op_end && *op_ptr != DW_OP_piece)
  	    error (_("DWARF-2 expression error: DW_OP_reg operations must be "
  		   "used either alone or in conjuction with DW_OP_piece."));
  
--- 411,419 ----
  	case DW_OP_reg29:
  	case DW_OP_reg30:
  	case DW_OP_reg31:
! 	  if (op_ptr != op_end 
! 	      && *op_ptr != DW_OP_piece
! 	      && *op_ptr != DW_OP_GNU_uninit)
  	    error (_("DWARF-2 expression error: DW_OP_reg operations must be "
  		   "used either alone or in conjuction with DW_OP_piece."));
  
*************** execute_stack_op (struct dwarf_expr_cont
*** 731,736 ****
--- 734,747 ----
            }
            goto no_push;
  
+ 	case DW_OP_GNU_uninit:
+ 	  if (op_ptr != op_end)
+ 	    error (_("DWARF-2 expression error: DW_OP_GNU_unint must always "
+ 		   "be the very last op."));
+ 
+ 	  ctx->initialized = 0;
+ 	  goto no_push;
+ 
  	default:
  	  error (_("Unhandled dwarf expression opcode 0x%x"), op);
  	}
Index: gdb/dwarf2expr.h
===================================================================
RCS file: /cvs/src/src/gdb/dwarf2expr.h,v
retrieving revision 1.9
diff -c -3 -p -r1.9 dwarf2expr.h
*** gdb/dwarf2expr.h	9 Jan 2007 17:58:50 -0000	1.9
--- gdb/dwarf2expr.h	17 May 2007 16:59:08 -0000
*************** struct dwarf_expr_context
*** 76,81 ****
--- 76,85 ----
       will be on the expression stack.  */
    int in_reg;
  
+   /* Initialization status of variable: Non-zero if variable has been
+      initialized; zero otherwise.  */
+   int initialized;
+ 
    /* An array of pieces.  PIECES points to its first element;
       NUM_PIECES is its length.
  
Index: gdb/dwarf2loc.c
===================================================================
RCS file: /cvs/src/src/gdb/dwarf2loc.c,v
retrieving revision 1.39
diff -c -3 -p -r1.39 dwarf2loc.c
*** gdb/dwarf2loc.c	24 Jan 2007 22:04:48 -0000	1.39
--- gdb/dwarf2loc.c	17 May 2007 16:59:08 -0000
*************** dwarf2_evaluate_loc_desc (struct symbol 
*** 256,261 ****
--- 256,263 ----
        VALUE_ADDRESS (retval) = address;
      }
  
+   set_value_initialized (retval, ctx->initialized);
+ 
    free_dwarf_expr_context (ctx);
  
    return retval;
Index: gdb/dwarf2read.c
===================================================================
RCS file: /cvs/src/src/gdb/dwarf2read.c,v
retrieving revision 1.218
diff -c -3 -p -r1.218 dwarf2read.c
*** gdb/dwarf2read.c	18 Apr 2007 13:25:04 -0000	1.218
--- gdb/dwarf2read.c	17 May 2007 16:59:08 -0000
*************** dwarf_stack_op_name (unsigned op)
*** 8629,8634 ****
--- 8629,8636 ----
        return "DW_OP_bit_piece";
      case DW_OP_GNU_push_tls_address:
        return "DW_OP_GNU_push_tls_address";
+     case DW_OP_GNU_uninit:
+       return "DW_OP_GNU_uninit";
      /* HP extensions. */ 
      case DW_OP_HP_is_value:
        return "DW_OP_HP_is_value";
*************** decode_locdesc (struct dwarf_block *blk,
*** 9204,9209 ****
--- 9206,9214 ----
  	    dwarf2_complex_location_expr_complaint ();
            break;
  
+ 	case DW_OP_GNU_uninit:
+ 	  break;
+ 
  	default:
  	  complaint (&symfile_complaints, _("unsupported stack op: '%s'"),
  		     dwarf_stack_op_name (op));
Index: gdb/value.c
===================================================================
RCS file: /cvs/src/src/gdb/value.c,v
retrieving revision 1.41
diff -c -3 -p -r1.41 value.c
*** gdb/value.c	13 Apr 2007 14:17:46 -0000	1.41
--- gdb/value.c	17 May 2007 16:59:08 -0000
*************** struct value
*** 157,162 ****
--- 157,165 ----
       actually exist in the program.  */
    char optimized_out;
  
+   /* If value is a variable, is it initialized or not.  */
+   int initialized;
+ 
    /* Actual contents of the value.  For use of this value; setting it
       uses the stuff above.  Not valid if lazy is nonzero.  Target
       byte-order.  We force it to be aligned properly for any possible
*************** allocate_value (struct type *type)
*** 232,237 ****
--- 235,241 ----
    val->embedded_offset = 0;
    val->pointed_to_offset = 0;
    val->modifiable = 1;
+   val->initialized = 1;  /* Default to initialized.  */
    return val;
  }
  
*************** using_struct_return (struct type *value_
*** 1691,1696 ****
--- 1695,1716 ----
  	  != RETURN_VALUE_REGISTER_CONVENTION);
  }
  
+ /* Set the initialized field in a value struct.  */
+ 
+ void
+ set_value_initialized (struct value *val, int status)
+ {
+   val->initialized = status;
+ }
+ 
+ /* Return the initialized field in a value struct.  */
+ 
+ int
+ value_initialized (struct value *val)
+ {
+   return val->initialized;
+ }
+ 
  void
  _initialize_values (void)
  {
Index: gdb/value.h
===================================================================
RCS file: /cvs/src/src/gdb/value.h,v
retrieving revision 1.96
diff -c -3 -p -r1.96 value.h
*** gdb/value.h	9 Jan 2007 17:58:59 -0000	1.96
--- gdb/value.h	17 May 2007 16:59:08 -0000
*************** extern int value_contents_equal (struct 
*** 193,198 ****
--- 193,204 ----
  extern int value_optimized_out (struct value *value);
  extern void set_value_optimized_out (struct value *value, int val);
  
+ /* Set or return field indicating whether a variable is initialized or
+    not, based on debugging information supplied by the compiler. 
+    1 = initialized; 0 = uninitialized.  */
+ extern int value_initialized (struct value *);
+ extern void set_value_initialized (struct value *, int);
+ 
  /* While the following fields are per- VALUE .CONTENT .PIECE (i.e., a
     single value might have multiple LVALs), this hacked interface is
     limited to just the first PIECE.  Expect further change.  */
Index: include/elf/dwarf2.h
===================================================================
RCS file: /cvs/src/src/include/elf/dwarf2.h,v
retrieving revision 1.19
diff -c -3 -p -r1.19 dwarf2.h
*** include/elf/dwarf2.h	2 Mar 2006 00:54:27 -0000	1.19
--- include/elf/dwarf2.h	17 May 2007 16:59:09 -0000
*************** enum dwarf_location_atom
*** 540,545 ****
--- 540,546 ----
      DW_OP_bit_piece = 0x9d,
      /* GNU extensions.  */
      DW_OP_GNU_push_tls_address = 0xe0,
+     DW_OP_GNU_uninit     = 0xf0,
      /* HP extensions.  */
      DW_OP_HP_unknown     = 0xe0, /* Ouch, the same as GNU_push_tls_address.  */
      DW_OP_HP_is_value    = 0xe1,

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On May 16, 2007, at 4:35 PM, Jim Blandy wrote:

>
> Caroline Tice <ctice@apple.com> writes:
>> I tested it by running it on a small test case I have
>> (with DW_OP_GNU_uninit ops in it), as well as running the
>> dejagnu testsuite with no regressions.  Is this modified patch okay
>> to commit to FSF GDB?
>
> Thanks for the revisions!  They look good.  I have a few more
> comments, mostly just details.
>
>> Index: gdb/c-valprint.c
>> ===================================================================
>> RCS file: /cvs/src/src/gdb/c-valprint.c,v
>> retrieving revision 1.42
>> diff -c -3 -p -r1.42 c-valprint.c
>> *** gdb/c-valprint.c	26 Jan 2007 20:54:16 -0000	1.42
>> --- gdb/c-valprint.c	9 May 2007 20:53:21 -0000
>> *************** c_value_print (struct value *val, struct
>> *** 556,561 ****
>> --- 556,564 ----
>>  	}
>>      }
>>
>> +   if (value_initialized (val) == 0)
>> +     fprintf_filtered (stream, " [uninitialized] ");
>> +
>>    if (objectprint && (TYPE_CODE (type) == TYPE_CODE_CLASS))
>>      {
>>        /* Attempt to determine real type of object */
>
> Nit-picky suggestion: wouldn't it be nicer to say "if (!
> value_initialized (val)) ..."?
>
>
>> *************** execute_stack_op (struct dwarf_expr_cont
>> *** 731,736 ****
>> --- 734,748 ----
>>            }
>>            goto no_push;
>>
>> + 	case DW_OP_GNU_uninit:
>> + 	  if (op_ptr != op_end
>> + 	      && *op_ptr != DW_OP_piece)
>> + 	    error (_("DWARF-2 expression error: DW_OP_reg operations  
>> must be "
>> + 		   "used either alone or in conjuction with DW_OP_piece."));
>> +
>> + 	  ctx->initialized = 0;
>> + 	  goto no_push;
>> +
>>  	default:
>>  	  error (_("Unhandled dwarf expression opcode 0x%x"), op);
>>  	}
>
> You said DW_OP_GNU_uninit doesn't apply to individual pieces.  So
> shouldn't this code report an error whenever DW_OP_GNU_uninit isn't
> the last opcode in the whole expression --- that is, even when it's
> followed by DW_OP_piece?
>
>> Index: gdb/dwarf2expr.h
>> ===================================================================
>> RCS file: /cvs/src/src/gdb/dwarf2expr.h,v
>> retrieving revision 1.9
>> diff -c -3 -p -r1.9 dwarf2expr.h
>> *** gdb/dwarf2expr.h	9 Jan 2007 17:58:50 -0000	1.9
>> --- gdb/dwarf2expr.h	9 May 2007 20:53:21 -0000
>> *************** struct dwarf_expr_context
>> *** 76,81 ****
>> --- 76,84 ----
>>       will be on the expression stack.  */
>>    int in_reg;
>>
>> +   /* Initialization status of variable.  */
>> +   int initialized;
>> +
>
> Another nit-pick: the comment should actually explain the
> interpretation of the value: "Non-zero if variable has been
> initialized; zero otherwise."
>
>> Index: gdb/value.h
>> ===================================================================
>> RCS file: /cvs/src/src/gdb/value.h,v
>> retrieving revision 1.96
>> diff -c -3 -p -r1.96 value.h
>> *** gdb/value.h	9 Jan 2007 17:58:59 -0000	1.96
>> --- gdb/value.h	9 May 2007 20:53:21 -0000
>> *************** extern int value_contents_equal (struct
>> *** 193,198 ****
>> --- 193,204 ----
>>  extern int value_optimized_out (struct value *value);
>>  extern void set_value_optimized_out (struct value *value, int val);
>>
>> + /* Set or return field indicating whether a variable is  
>> initialized or
>> +    not, based on DWARF location information supplied by the  
>> compiler.
>> +    1 = initialized; 0 = uninitialized.  */
>> + extern int value_initialized (struct value *);
>> + extern void set_value_initialized (struct value *, int);
>> +
>>  /* While the following fields are per- VALUE .CONTENT .PIECE  
>> (i.e., a
>>     single value might have multiple LVALs), this hacked interface is
>>     limited to just the first PIECE.  Expect further change.  */
>
> A final nit-pick: value.h, value.c, and so on are meant to be
> independent of any particular debugging format.  There should never be
> DWARF dependencies here.  Your code does this right --- a generic
> mechanism to be used by DWARF-specific code in the appropriate way ---
> but the comment should also not suggest that it's DWARF-specific.
> Thus, "... based on debugging information supplied by the compiler".