[PATCH] Fix invalid DW_AT_{lower,upper}_bound attributes (PR debug/43237)

[Jakub Jelinek]

Hi!

I've noticed
readelf -wo gcc/cc1 >/dev/null
readelf: Warning: There is a hole [0xd48fba - 0xd48fea] in .debug_loc section.
readelf: Warning: There is a hole [0xd49311 - 0xd49381] in .debug_loc section.
errors today.  The problem is that if the artificial VAR_DECL for the
VLA bound doesn't have always the same location expression (or isn't valid
through the whole lifetime) we attempt to emit DW_AT_upper_bound as
loclistptr, which is not valid for this attribute.  DW_AT_upper_bound can be
a constant, or an expression block (that is when the list is single
element), or a reference.  The following patch fixes it by emitting a
reference to an artificial DW_TAG_variable with the loclistptr in
DW_AT_location.

Bootstrapped/regtested on x86_64-linux and i686-linux, the readelf -wo
warnings are gone.  Ok for trunk?

2010-03-02  Jakub Jelinek  <jakub@redhat.com>

	PR debug/43237
	* dwarf2out.c (add_bound_info): If a decl bound doesn't have decl_die,
	fallthrough to default handling, just with want_address 0 instead of 2.
	For single element lists, add_AT_loc directly, otherwise create an
	artificial variable DIE and stick location list to it.

	* gcc.dg/debug/dwarf2/pr43237.c: New test.

--- gcc/dwarf2out.c.jj	2010-02-19 09:23:10.000000000 +0100
+++ gcc/dwarf2out.c	2010-03-02 20:02:38.000000000 +0100
@@ -16275,6 +16275,8 @@ add_comp_dir_attribute (dw_die_ref die)
 static void
 add_bound_info (dw_die_ref subrange_die, enum dwarf_attribute bound_attr, tree bound)
 {
+  int want_address = 2;
+
   switch (TREE_CODE (bound))
     {
     case ERROR_MARK:
@@ -16324,7 +16326,6 @@ add_bound_info (dw_die_ref subrange_die,
     case RESULT_DECL:
       {
 	dw_die_ref decl_die = lookup_decl_die (bound);
-	dw_loc_list_ref loc;
 
 	/* ??? Can this happen, or should the variable have been bound
 	   first?  Probably it can, since I imagine that we try to create
@@ -16332,14 +16333,13 @@ add_bound_info (dw_die_ref subrange_die,
 	   the list, and won't have created a forward reference to a
 	   later parameter.  */
 	if (decl_die != NULL)
-	  add_AT_die_ref (subrange_die, bound_attr, decl_die);
-	else
 	  {
-	    loc = loc_list_from_tree (bound, 0);
-	    add_AT_location_description (subrange_die, bound_attr, loc);
+	    add_AT_die_ref (subrange_die, bound_attr, decl_die);
+	    break;
 	  }
-	break;
+	want_address = 0;
       }
+      /* FALLTHRU */
 
     default:
       {
@@ -16349,10 +16349,16 @@ add_bound_info (dw_die_ref subrange_die,
 	dw_die_ref ctx, decl_die;
 	dw_loc_list_ref list;
 
-	list = loc_list_from_tree (bound, 2);
+	list = loc_list_from_tree (bound, want_address);
 	if (list == NULL)
 	  break;
 
+	if (single_element_loc_list_p (list))
+	  {
+	    add_AT_loc (subrange_die, bound_attr, list->expr);
+	    break;
+	  }
+
 	if (current_function_decl == 0)
 	  ctx = comp_unit_die;
 	else
@@ -16361,11 +16367,7 @@ add_bound_info (dw_die_ref subrange_die,
 	decl_die = new_die (DW_TAG_variable, ctx, bound);
 	add_AT_flag (decl_die, DW_AT_artificial, 1);
 	add_type_attribute (decl_die, TREE_TYPE (bound), 1, 0, ctx);
-	if (list->dw_loc_next)
-	  add_AT_loc_list (decl_die, DW_AT_location, list);
-	else
-	  add_AT_loc (decl_die, DW_AT_location, list->expr);
-
+	add_AT_location_description (decl_die, DW_AT_location, list);
 	add_AT_die_ref (subrange_die, bound_attr, decl_die);
 	break;
       }
--- gcc/testsuite/gcc.dg/debug/dwarf2/pr43237.c.jj	2010-03-02 21:51:41.000000000 +0100
+++ gcc/testsuite/gcc.dg/debug/dwarf2/pr43237.c	2010-03-02 21:52:37.000000000 +0100
@@ -0,0 +1,31 @@
+/* PR debug/43237 */
+/* { dg-do compile } */
+/* { dg-options "-g -O2 -dA -fno-merge-debug-strings" } */
+
+struct S
+{
+  int *a;
+  int b;
+  int **c;
+  int d;
+};
+
+void foo (struct S *);
+void bar (struct S *);
+
+int
+baz (void)
+{
+  struct S s;
+  foo (&s);
+  {
+    int a[s.b];
+    int *c[s.d];
+    s.a = a;
+    s.c = c;
+    bar (&s);
+  }
+  return 0;
+}
+
+/* { dg-final { scan-assembler-not "LLST\[^\\r\\n\]*DW_AT_upper_bound" } } */

	Jakub