Catch exception in value_rtti_indirect_type

In the situation described in bug 17416 [1]:

  * "set print object" is on;
  * The variable object is a pointer to a struct, and it contains an
    invalid value (e.g. NULL, or random uninitialized value);
  * The variable object (struct) has a child which is also a pointer to a
    struct;
  * We try to use "-var-list-children".

... an exception thrown in value_ind can propagate too far and leave an
half-built variable object, leading to a wrong state. This patch adds a
TRY_CATCH to catch it and makes value_rtti_indirect_type return NULL in
that case, meaning that the type of the pointed object could not be
found.

A test for the fix is also added.

New in v2:

  * Added test.
  * Restructured "catch" code.
  * Added details about the bug in commit log.

gdb/Changelog:

	* valops.c (value_rtti_indirect_type): Catch exception thrown by
	value_ind.

gdb/testsuite/ChangeLog

	* gdb.mi/mi-var-list-children-invalid-grandchild.c: New file.
	* gdb.mi/mi-var-list-children-invalid-grandchild.exp: New file.

[1] https://sourceware.org/bugzilla/show_bug.cgi?id=17416

1 files changed, 20 insertions, 2 deletions

diff --git a/gdb/valops.c b/gdb/valops.c
index 27eda9f..8cbac85 100644
--- a/gdb/valops.c
+++ b/gdb/valops.c
@@ -3592,7 +3592,7 @@ struct type *
 value_rtti_indirect_type (struct value *v, int *full, 
 			  int *top, int *using_enc)
 {
-  struct value *target;
+  struct value *target = NULL;
   struct type *type, *real_type, *target_type;
 
   type = value_type (v);
@@ -3600,7 +3600,25 @@ value_rtti_indirect_type (struct value *v, int *full,
   if (TYPE_CODE (type) == TYPE_CODE_REF)
     target = coerce_ref (v);
   else if (TYPE_CODE (type) == TYPE_CODE_PTR)
-    target = value_ind (v);
+    {
+      volatile struct gdb_exception except;
+
+      TRY_CATCH (except, RETURN_MASK_ERROR)
+        {
+	  target = value_ind (v);
+        }
+      if (except.reason < 0)
+	{
+	  if (except.error == MEMORY_ERROR)
+	    {
+	      /* value_ind threw a memory error. The pointer is NULL or
+	         contains an uninitialized value: we can't determine any
+	         type.  */
+	      return NULL;
+	    }
+	  throw_exception (except);
+	}
+    }
   else
     return NULL;