[patch] MI: Error out on -var-create invalid FRAME-ADDR

[Jan Kratochvil <jan.kratochvil@redhat.com>]

Hi,

-var-create could create VAROBJ with uninitialized thread_id leading to
unexpected processing.

The frame parameter of -var-create is FRAME-ADDR, one could expect it is
FRAME-ID.  It is even commented in the source:
	    /* FIXME: cagney/2002-11-23: This code should be doing a
	       lookup using the frame ID and not just the frame's
	       ``address''.  This, of course, means an interface
	       change.  However, with out that interface change ISAs,
	       such as the ia64 with its two stacks, won't work.
	       Similar goes for the case where there is a frameless
	       function.  */
	    fi = find_frame_addr_in_frame_chain (frame);

At least error out when the frame is not found AND it harms.

Therefore the original command Dodji bugreporting it:
	-var-create var2 0 variable
should have been instead:
	-var-create --thread 1 --frame 0 var2 * variable

Regression tested on {x86_64,i686}-fedora11-linux-gnu.

find_frame_addr_in_frame_chain already has an explicit check for 0 so 0
currently can never be a valid frame address on any arch:
  if (frame_addr == (CORE_ADDR) 0)
    return NULL;


Thanks,
Jan


gdb/
2009-08-10  Jan Kratochvil  <jan.kratochvil@redhat.com>

	* varobj.c (varobj_create): Error if the specified frame was not found
	and it is needed.

gdb/testsuite/
2009-08-10  Jan Kratochvil  <jan.kratochvil@redhat.com>

	* gdb.mi/mi2-var-cmd.exp (create variable with invalid FRAME-ADDR): New.

--- a/gdb/testsuite/gdb.mi/mi2-var-cmd.exp
+++ b/gdb/testsuite/gdb.mi/mi2-var-cmd.exp
@@ -126,6 +126,11 @@ mi_gdb_test "-var-create int * int" \
 	"&\"Attempt to use a type name as an expression.\\\\n\".*\\^error,msg=\"mi_cmd_var_create: unable to create variable object\"" \
 	"create int"
 
+# The number 0 must be an invalid frame address and linteger a local variable.
+mi_gdb_test "-var-create invalidframe 0 linteger" \
+	"&\"Failed to find the specified frame.\\\\n\".*\\^error,msg=\"mi_cmd_var_create: unable to create variable object\"" \
+	"create variable with invalid FRAME-ADDR"
+
 
 #####             #####
 #                     #
--- a/gdb/varobj.c
+++ b/gdb/varobj.c
@@ -565,8 +567,19 @@ varobj_create (char *objname,
          we must select the appropriate frame before parsing
          the expression, otherwise the value will not be current.
          Since select_frame is so benign, just call it for all cases. */
-      if (innermost_block && fi != NULL)
+      if (innermost_block)
 	{
+	  /* User could specify explicit FRAME-ADDR which was not found but
+	     EXPRESSION is frame specific and we would not be able to evaluate
+	     it correctly next time.  With VALID_BLOCK set we must also set
+	     FRAME and THREAD_ID.  */
+	  if (fi == NULL)
+	    {
+	      fprintf_unfiltered (gdb_stderr, "Failed to find the specified"
+				  " frame.\n");
+	      return NULL;
+	    }
+
 	  var->root->frame = get_frame_id (fi);
 	  var->root->thread_id = pid_to_thread_id (inferior_ptid);
 	  old_fi = get_selected_frame (NULL);