gdb/

	* findvar.c (read_var_value): Never return NULL, throw an error
	instead.  Update the function comment.  State symbol name in the error
	messages.
	* python/py-frame.c (frapy_read_var): Remove handling of NULL from
	read_var_value.
	* stack.c (print_frame_args): Likewise.
	* valops.c (value_of_variable): Likewise.

5 files changed, 41 insertions, 43 deletions

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index e7f3da7..9f4697a 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,5 +1,15 @@
 2011-09-08  Jan Kratochvil  <jan.kratochvil@redhat.com>
 
+	* findvar.c (read_var_value): Never return NULL, throw an error
+	instead.  Update the function comment.  State symbol name in the error
+	messages.
+	* python/py-frame.c (frapy_read_var): Remove handling of NULL from
+	read_var_value.
+	* stack.c (print_frame_args): Likewise.
+	* valops.c (value_of_variable): Likewise.
+
+2011-09-08  Jan Kratochvil  <jan.kratochvil@redhat.com>
+
 	* stack.c (print_frame_args): New variable except.  Wrap
 	read_var_value and common_val_print into TRY_CATCH.
 
diff --git a/gdb/findvar.c b/gdb/findvar.c
index 69dc5a0..8e986f1 100644
--- a/gdb/findvar.c
+++ b/gdb/findvar.c
@@ -409,7 +409,7 @@ symbol_read_needs_frame (struct symbol *sym)
 /* Given a struct symbol for a variable,
    and a stack frame id, read the value of the variable
    and return a (pointer to a) struct value containing the value.
-   If the variable cannot be found, return a zero pointer.  */
+   If the variable cannot be found, throw error.  */
 
 struct value *
 read_var_value (struct symbol *var, struct frame_info *frame)
@@ -477,7 +477,8 @@ read_var_value (struct symbol *var, struct frame_info *frame)
     case LOC_ARG:
       addr = get_frame_args_address (frame);
       if (!addr)
-	return 0;
+	error (_("Unknown argument list address for `%s'."),
+	       SYMBOL_PRINT_NAME (var));
       addr += SYMBOL_VALUE (var);
       v = allocate_value_lazy (type);
       break;
@@ -489,7 +490,8 @@ read_var_value (struct symbol *var, struct frame_info *frame)
 
 	argref = get_frame_args_address (frame);
 	if (!argref)
-	  return 0;
+	  error (_("Unknown argument list address for `%s'."),
+		 SYMBOL_PRINT_NAME (var));
 	argref += SYMBOL_VALUE (var);
 	ref = value_at (lookup_pointer_type (type), argref);
 	addr = value_as_address (ref);
@@ -504,7 +506,8 @@ read_var_value (struct symbol *var, struct frame_info *frame)
       break;
 
     case LOC_TYPEDEF:
-      error (_("Cannot look up value of a typedef"));
+      error (_("Cannot look up value of a typedef `%s'."),
+	     SYMBOL_PRINT_NAME (var));
       break;
 
     case LOC_BLOCK:
@@ -530,7 +533,8 @@ read_var_value (struct symbol *var, struct frame_info *frame)
 					  frame);
 
 	    if (regval == NULL)
-	      error (_("Value of register variable not available."));
+	      error (_("Value of register variable not available for `%s'."),
+	             SYMBOL_PRINT_NAME (var));
 
 	    addr = value_as_address (regval);
 	    v = allocate_value_lazy (type);
@@ -540,7 +544,8 @@ read_var_value (struct symbol *var, struct frame_info *frame)
 	    regval = value_from_register (type, regno, frame);
 
 	    if (regval == NULL)
-	      error (_("Value of register variable not available."));
+	      error (_("Value of register variable not available for `%s'."),
+	             SYMBOL_PRINT_NAME (var));
 	    return regval;
 	  }
       }
@@ -561,7 +566,7 @@ read_var_value (struct symbol *var, struct frame_info *frame)
 
 	msym = lookup_minimal_symbol (SYMBOL_LINKAGE_NAME (var), NULL, NULL);
 	if (msym == NULL)
-	  return 0;
+	  error (_("No global symbol \"%s\"."), SYMBOL_LINKAGE_NAME (var));
 	if (overlay_debugging)
 	  addr = symbol_overlayed_address (SYMBOL_VALUE_ADDRESS (msym),
 					   SYMBOL_OBJ_SECTION (msym));
@@ -580,7 +585,8 @@ read_var_value (struct symbol *var, struct frame_info *frame)
       return allocate_optimized_out_value (type);
 
     default:
-      error (_("Cannot look up value of a botched symbol."));
+      error (_("Cannot look up value of a botched symbol `%s'."),
+	     SYMBOL_PRINT_NAME (var));
       break;
     }
 
diff --git a/gdb/python/py-frame.c b/gdb/python/py-frame.c
index 7efd13f..9143367 100644
--- a/gdb/python/py-frame.c
+++ b/gdb/python/py-frame.c
@@ -467,14 +467,6 @@ frapy_read_var (PyObject *self, PyObject *args)
     }
   GDB_PY_HANDLE_EXCEPTION (except);
 
-  if (!val)
-    {
-      PyErr_Format (PyExc_ValueError,
-		    _("Variable cannot be found for symbol '%s'."),
-		    SYMBOL_NATURAL_NAME (var));
-      return NULL;
-    }
-
   return value_to_value_object (val);
 }
 
diff --git a/gdb/stack.c b/gdb/stack.c
index 3147f3e..15666ee 100644
--- a/gdb/stack.c
+++ b/gdb/stack.c
@@ -330,6 +330,9 @@ print_frame_args (struct symbol *func, struct frame_info *frame,
 
 	      TRY_CATCH (except, RETURN_MASK_ERROR)
 		{
+		  const struct language_defn *language;
+		  struct value_print_options opts;
+
 		  /* Avoid value_print because it will deref ref parameters.
 		     We just want to print their addresses.  Print ??? for
 		     args whose address we do not know.  We pass 2 as
@@ -338,29 +341,21 @@ print_frame_args (struct symbol *func, struct frame_info *frame,
 		     recurse.  */
 		  val = read_var_value (sym, frame);
 
-		  annotate_arg_value (val == NULL ? NULL : value_type (val));
+		  annotate_arg_value (value_type (val));
 
-		  if (val)
-		    {
-		      const struct language_defn *language;
-		      struct value_print_options opts;
-
-		      /* Use the appropriate language to display our symbol,
-			 unless the user forced the language to a specific
-			 language.  */
-		      if (language_mode == language_mode_auto)
-			language = language_def (SYMBOL_LANGUAGE (sym));
-		      else
-			language = current_language;
-
-		      get_raw_print_options (&opts);
-		      opts.deref_ref = 0;
-		      opts.summary = summary;
-		      common_val_print (val, stb->stream, 2, &opts, language);
-		      ui_out_field_stream (uiout, "value", stb);
-		    }
+		  /* Use the appropriate language to display our symbol,
+		     unless the user forced the language to a specific
+		     language.  */
+		  if (language_mode == language_mode_auto)
+		    language = language_def (SYMBOL_LANGUAGE (sym));
 		  else
-		    ui_out_text (uiout, "???");
+		    language = current_language;
+
+		  get_raw_print_options (&opts);
+		  opts.deref_ref = 0;
+		  opts.summary = summary;
+		  common_val_print (val, stb->stream, 2, &opts, language);
+		  ui_out_field_stream (uiout, "value", stb);
 		}
 	      if (except.reason < 0)
 		{
diff --git a/gdb/valops.c b/gdb/valops.c
index 25e0fc3..32d71cd 100644
--- a/gdb/valops.c
+++ b/gdb/valops.c
@@ -1488,7 +1488,6 @@ value_repeat (struct value *arg1, int count)
 struct value *
 value_of_variable (struct symbol *var, struct block *b)
 {
-  struct value *val;
   struct frame_info *frame;
 
   if (!symbol_read_needs_frame (var))
@@ -1509,11 +1508,7 @@ value_of_variable (struct symbol *var, struct block *b)
 	}
     }
 
-  val = read_var_value (var, frame);
-  if (!val)
-    error (_("Address of symbol \"%s\" is unknown."), SYMBOL_PRINT_NAME (var));
-
-  return val;
+  return read_var_value (var, frame);
 }
 
 struct value *