[RFA 6/8] Use value_freer in dwarf2_evaluate_loc_desc_full

[Tom Tromey <tom@tromey.com>]

This changes dwarf2_evaluate_loc_desc_full to use value_freer.

Note that this function previously called do_cleanup using the same
cleanup multiple times.  I had thought this was buggy, but re-reading
make_my_cleanup2 indicates that it is not.  Nevertheless it is
surprising, and at least one of the calls (the one that is completely
removed in this patch) seems to have been done under the assumption
that it would still have some effect.

2016-11-28  Tom Tromey  <tom@tromey.com>

	* value.h (value_freer::~value_freer): Call release.
	(value_freer::release): New method.
	* dwarf2loc.c (dwarf2_evaluate_loc_desc_full): Use value_freer.
---
 gdb/ChangeLog   |  6 ++++++
 gdb/dwarf2loc.c | 27 +++++++++++++--------------
 gdb/value.h     | 12 +++++++++++-
 3 files changed, 30 insertions(+), 15 deletions(-)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 6197bfb..cf61306 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,5 +1,11 @@
 2016-11-28  Tom Tromey  <tom@tromey.com>
 
+	* value.h (value_freer::~value_freer): Call release.
+	(value_freer::release): New method.
+	* dwarf2loc.c (dwarf2_evaluate_loc_desc_full): Use value_freer.
+
+2016-11-28  Tom Tromey  <tom@tromey.com>
+
 	* python/py-value.c (valpy_dereference, valpy_referenced_value)
 	(valpy_reference_value, valpy_const_value, valpy_get_address)
 	(valpy_get_dynamic_type, valpy_lazy_string, valpy_do_cast)
diff --git a/gdb/dwarf2loc.c b/gdb/dwarf2loc.c
index 0d8a47c..43c95b8 100644
--- a/gdb/dwarf2loc.c
+++ b/gdb/dwarf2loc.c
@@ -2321,7 +2321,6 @@ dwarf2_evaluate_loc_desc_full (struct type *type, struct frame_info *frame,
 			       LONGEST byte_offset)
 {
   struct value *retval;
-  struct cleanup *value_chain;
   struct objfile *objfile = dwarf2_per_cu_objfile (per_cu);
 
   if (byte_offset < 0)
@@ -2335,7 +2334,7 @@ dwarf2_evaluate_loc_desc_full (struct type *type, struct frame_info *frame,
   ctx.per_cu = per_cu;
   ctx.obj_address = 0;
 
-  value_chain = make_cleanup_value_free_to_mark (value_mark ());
+  value_freer free_values;
 
   ctx.gdbarch = get_objfile_arch (objfile);
   ctx.addr_size = dwarf2_per_cu_addr_size (per_cu);
@@ -2350,7 +2349,7 @@ dwarf2_evaluate_loc_desc_full (struct type *type, struct frame_info *frame,
     {
       if (ex.error == NOT_AVAILABLE_ERROR)
 	{
-	  do_cleanups (value_chain);
+	  free_values.release ();
 	  retval = allocate_value (type);
 	  mark_value_bytes_unavailable (retval, 0, TYPE_LENGTH (type));
 	  return retval;
@@ -2359,7 +2358,7 @@ dwarf2_evaluate_loc_desc_full (struct type *type, struct frame_info *frame,
 	{
 	  if (entry_values_debug)
 	    exception_print (gdb_stdout, ex);
-	  do_cleanups (value_chain);
+	  free_values.release ();
 	  return allocate_optimized_out_value (type);
 	}
       else
@@ -2382,7 +2381,7 @@ dwarf2_evaluate_loc_desc_full (struct type *type, struct frame_info *frame,
 				  ctx.addr_size, frame);
       /* We must clean up the value chain after creating the piece
 	 closure but before allocating the result.  */
-      do_cleanups (value_chain);
+      free_values.release ();
       retval = allocate_computed_value (type, &pieced_value_funcs, c);
       set_value_offset (retval, byte_offset);
     }
@@ -2399,7 +2398,7 @@ dwarf2_evaluate_loc_desc_full (struct type *type, struct frame_info *frame,
 
 	    if (byte_offset != 0)
 	      error (_("cannot use offset on synthetic pointer to register"));
-	    do_cleanups (value_chain);
+	    free_values.release ();
 	    retval = value_from_register (type, gdb_regnum, frame);
 	    if (value_optimized_out (retval))
 	      {
@@ -2411,7 +2410,6 @@ dwarf2_evaluate_loc_desc_full (struct type *type, struct frame_info *frame,
 		   inspecting a register ($pc, $sp, etc.), return a
 		   generic optimized out value instead, so that we show
 		   <optimized out> instead of <not saved>.  */
-		do_cleanups (value_chain);
 		tmp = allocate_value (type);
 		value_contents_copy (tmp, 0, retval, 0, TYPE_LENGTH (type));
 		retval = tmp;
@@ -2445,7 +2443,7 @@ dwarf2_evaluate_loc_desc_full (struct type *type, struct frame_info *frame,
 	      }
 	    address = value_as_address (value_from_pointer (ptr_type, address));
 
-	    do_cleanups (value_chain);
+	    free_values.release ();
 	    retval = value_at_lazy (type, address + byte_offset);
 	    if (in_stack_memory)
 	      set_value_stack (retval, 1);
@@ -2458,6 +2456,7 @@ dwarf2_evaluate_loc_desc_full (struct type *type, struct frame_info *frame,
 	    gdb_byte *contents;
 	    const gdb_byte *val_bytes;
 	    size_t n = TYPE_LENGTH (value_type (value));
+	    struct cleanup *cleanup;
 
 	    if (byte_offset + TYPE_LENGTH (type) > n)
 	      invalid_synthetic_pointer ();
@@ -2470,8 +2469,8 @@ dwarf2_evaluate_loc_desc_full (struct type *type, struct frame_info *frame,
 	       to the mark, but we still need the value contents
 	       below.  */
 	    value_incref (value);
-	    do_cleanups (value_chain);
-	    make_cleanup_value_free (value);
+	    free_values.release ();
+	    cleanup = make_cleanup_value_free (value);
 
 	    retval = allocate_value (type);
 	    contents = value_contents_raw (retval);
@@ -2484,6 +2483,8 @@ dwarf2_evaluate_loc_desc_full (struct type *type, struct frame_info *frame,
 		n = TYPE_LENGTH (type);
 	      }
 	    memcpy (contents, val_bytes, n);
+
+	    do_cleanups (cleanup);
 	  }
 	  break;
 
@@ -2496,7 +2497,7 @@ dwarf2_evaluate_loc_desc_full (struct type *type, struct frame_info *frame,
 	    if (byte_offset + TYPE_LENGTH (type) > n)
 	      invalid_synthetic_pointer ();
 
-	    do_cleanups (value_chain);
+	    free_values.release ();
 	    retval = allocate_value (type);
 	    contents = value_contents_raw (retval);
 
@@ -2516,7 +2517,7 @@ dwarf2_evaluate_loc_desc_full (struct type *type, struct frame_info *frame,
 	  break;
 
 	case DWARF_VALUE_OPTIMIZED_OUT:
-	  do_cleanups (value_chain);
+	  free_values.release ();
 	  retval = allocate_optimized_out_value (type);
 	  break;
 
@@ -2532,8 +2533,6 @@ dwarf2_evaluate_loc_desc_full (struct type *type, struct frame_info *frame,
 
   set_value_initialized (retval, ctx.initialized);
 
-  do_cleanups (value_chain);
-
   return retval;
 }
 
diff --git a/gdb/value.h b/gdb/value.h
index 399bf48..43dfe14 100644
--- a/gdb/value.h
+++ b/gdb/value.h
@@ -728,7 +728,17 @@ class value_freer
 
   ~value_freer ()
   {
-    value_free_to_mark (m_value);
+    release ();
+  }
+
+  /* Free the values currently on the value stack.  */
+  void release ()
+  {
+    if (m_value != NULL)
+      {
+	value_free_to_mark (m_value);
+	m_value = NULL;
+      }
   }
 
  private:
-- 
2.7.4