Re: [RFA 6/8] Use value_freer in dwarf2_evaluate_loc_desc_full

[Tom Tromey <tom@tromey.com>]

Tom> It looks good to me.  I've made this change and I'll send the new
Tom> patches soon.

Here's the new version of the patch to use scoped_value_mark in
dwarf2_evaluate_loc_desc_full.

Tom

commit 63b869373e8dff9fd8648c00712459dd18a9798b
Author: Tom Tromey <tom@tromey.com>
Date:   Mon Nov 21 21:04:59 2016 -0700

    Use scoped_value_mark in dwarf2_evaluate_loc_desc_full
    
    This changes dwarf2_evaluate_loc_desc_full to use scoped_value_mark.
    
    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.
    
    2016-12-13  Tom Tromey  <tom@tromey.com>
    
    	* value.h (scoped_value_mark::~scoped_value_mark): Call
    	free_to_mark.
    	(scoped_value_mark::free_to_mark): New method.
    	* dwarf2loc.c (dwarf2_evaluate_loc_desc_full): Use
    	scoped_value_mark.

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 01ef9d6..d402851 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,5 +1,13 @@
 2016-12-13  Tom Tromey  <tom@tromey.com>
 
+	* value.h (scoped_value_mark::~scoped_value_mark): Call
+	free_to_mark.
+	(scoped_value_mark::free_to_mark): New method.
+	* dwarf2loc.c (dwarf2_evaluate_loc_desc_full): Use
+	scoped_value_mark.
+
+2016-12-13  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 f5ab371..6e36835 100644
--- a/gdb/dwarf2loc.c
+++ b/gdb/dwarf2loc.c
@@ -2283,7 +2283,6 @@ 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)
@@ -2297,7 +2296,7 @@ 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 ());
+  scoped_value_mark free_values;
 
   ctx.gdbarch = get_objfile_arch (objfile);
   ctx.addr_size = dwarf2_per_cu_addr_size (per_cu);
@@ -2312,7 +2311,7 @@ dwarf2_evaluate_loc_desc_full (struct type *type, struct frame_info *frame,
     {
       if (ex.error == NOT_AVAILABLE_ERROR)
 	{
-	  do_cleanups (value_chain);
+	  free_values.free_to_mark ();
 	  retval = allocate_value (type);
 	  mark_value_bytes_unavailable (retval, 0, TYPE_LENGTH (type));
 	  return retval;
@@ -2321,7 +2320,7 @@ 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.free_to_mark ();
 	  return allocate_optimized_out_value (type);
 	}
       else
@@ -2344,7 +2343,7 @@ 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.free_to_mark ();
       retval = allocate_computed_value (type, &pieced_value_funcs, c);
       set_value_offset (retval, byte_offset);
     }
@@ -2361,7 +2360,7 @@ 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.free_to_mark ();
 	    retval = value_from_register (type, gdb_regnum, frame);
 	    if (value_optimized_out (retval))
 	      {
@@ -2373,7 +2372,6 @@ 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;
@@ -2407,7 +2405,7 @@ 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.free_to_mark ();
 	    retval = value_at_lazy (type, address + byte_offset);
 	    if (in_stack_memory)
 	      set_value_stack (retval, 1);
@@ -2420,6 +2418,7 @@ 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 ();
@@ -2432,8 +2431,8 @@ 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.free_to_mark ();
+	    cleanup = make_cleanup_value_free (value);
 
 	    retval = allocate_value (type);
 	    contents = value_contents_raw (retval);
@@ -2446,6 +2445,8 @@ 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;
 
@@ -2458,7 +2459,7 @@ 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.free_to_mark ();
 	    retval = allocate_value (type);
 	    contents = value_contents_raw (retval);
 
@@ -2478,7 +2479,7 @@ dwarf2_evaluate_loc_desc_full (struct type *type, struct frame_info *frame,
 	  break;
 
 	case DWARF_VALUE_OPTIMIZED_OUT:
-	  do_cleanups (value_chain);
+	  free_values.free_to_mark ();
 	  retval = allocate_optimized_out_value (type);
 	  break;
 
@@ -2494,8 +2495,6 @@ 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 3a0641a..d261148 100644
--- a/gdb/value.h
+++ b/gdb/value.h
@@ -728,7 +728,17 @@ class scoped_value_mark
 
   ~scoped_value_mark ()
   {
-    value_free_to_mark (m_value);
+    free_to_mark ();
+  }
+
+  /* Free the values currently on the value stack.  */
+  void free_to_mark ()
+  {
+    if (m_value != NULL)
+      {
+	value_free_to_mark (m_value);
+	m_value = NULL;
+      }
   }
 
  private: