gdb/

	Fix empty DWARF expressions DATA vs. SIZE conditionals.
	* dwarf2loc.c (dwarf2_find_location_expression): Clear *LOCEXPR_LENGTH.
	(dwarf_expr_frame_base_1): Indicate unavailability via zero *LENGTH.
	(locexpr_tracepoint_var_ref): Check only zero SIZE, not zero DATA.
	(loclist_read_variable, loclist_tracepoint_var_ref): Do not check for
	zero DATA.
	* dwarf2loc.h (struct dwarf2_locexpr_baton): Comment DATA vs. SIZE
	validity.
	* dwarf2read.c (struct dwarf_block): Comment DATA validity.
	(dwarf2_fetch_die_location_block, dwarf2_symbol_mark_computed): Do not
	clear DATA on zero SIZE.

gdb/testsuite/
	Fix empty DWARF expressions DATA vs. SIZE conditionals.
	* gdb.dwarf2/dw2-op-call.S (arraycallnoloc, arraynoloc): New DIEs.
	(loclist): New.
	(4): New abbrev.
	* gdb.dwarf2/dw2-op-call.exp: Remove variable srcfile and executable.
	Use prepare_for_testing, remove clean_restart.
	(p arraynoloc, p arraycallnoloc): New tests.

7 files changed, 81 insertions, 21 deletions

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 56d7f7c..ba80e5a 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,17 @@
+2011-10-12  Jan Kratochvil  <jan.kratochvil@redhat.com>
+
+	Fix empty DWARF expressions DATA vs. SIZE conditionals.
+	* dwarf2loc.c (dwarf2_find_location_expression): Clear *LOCEXPR_LENGTH.
+	(dwarf_expr_frame_base_1): Indicate unavailability via zero *LENGTH.
+	(locexpr_tracepoint_var_ref): Check only zero SIZE, not zero DATA.
+	(loclist_read_variable, loclist_tracepoint_var_ref): Do not check for
+	zero DATA.
+	* dwarf2loc.h (struct dwarf2_locexpr_baton): Comment DATA vs. SIZE
+	validity.
+	* dwarf2read.c (struct dwarf_block): Comment DATA validity.
+	(dwarf2_fetch_die_location_block, dwarf2_symbol_mark_computed): Do not
+	clear DATA on zero SIZE.
+
 2011-10-12  Doug Evans  <dje@google.com>
 
 	* dwarf2read.c (partial_read_comp_unit_head): Set header->offset,
diff --git a/gdb/dwarf2loc.c b/gdb/dwarf2loc.c
index 7eb8d8a..8a7d7e9 100644
--- a/gdb/dwarf2loc.c
+++ b/gdb/dwarf2loc.c
@@ -112,7 +112,10 @@ dwarf2_find_location_expression (struct dwarf2_loclist_baton *baton,
 
       /* An end-of-list entry.  */
       if (low == 0 && high == 0)
-	return NULL;
+	{
+	  *locexpr_length = 0;
+	  return NULL;
+	}
 
       /* Otherwise, a location expression entry.  */
       low += base_address;
@@ -215,7 +218,7 @@ dwarf_expr_frame_base_1 (struct symbol *framefunc, CORE_ADDR pc,
 			 const gdb_byte **start, size_t *length)
 {
   if (SYMBOL_LOCATION_BATON (framefunc) == NULL)
-    *start = NULL;
+    *length = 0;
   else if (SYMBOL_COMPUTED_OPS (framefunc) == &dwarf2_loclist_funcs)
     {
       struct dwarf2_loclist_baton *symbaton;
@@ -234,10 +237,10 @@ dwarf_expr_frame_base_1 (struct symbol *framefunc, CORE_ADDR pc,
 	  *start = symbaton->data;
 	}
       else
-	*start = NULL;
+	*length = 0;
     }
 
-  if (*start == NULL)
+  if (*length == 0)
     error (_("Could not find the frame base for \"%s\"."),
 	   SYMBOL_NATURAL_NAME (framefunc));
 }
@@ -3716,7 +3719,7 @@ locexpr_tracepoint_var_ref (struct symbol *symbol, struct gdbarch *gdbarch,
   struct dwarf2_locexpr_baton *dlbaton = SYMBOL_LOCATION_BATON (symbol);
   unsigned int addr_size = dwarf2_per_cu_addr_size (dlbaton->per_cu);
 
-  if (dlbaton->data == NULL || dlbaton->size == 0)
+  if (dlbaton->size == 0)
     value->optimized_out = 1;
   else
     dwarf2_compile_expr_to_ax (ax, value, gdbarch, addr_size,
@@ -3750,11 +3753,8 @@ loclist_read_variable (struct symbol *symbol, struct frame_info *frame)
   CORE_ADDR pc = frame ? get_frame_address_in_block (frame) : 0;
 
   data = dwarf2_find_location_expression (dlbaton, &size, pc);
-  if (data == NULL)
-    val = allocate_optimized_out_value (SYMBOL_TYPE (symbol));
-  else
-    val = dwarf2_evaluate_loc_desc (SYMBOL_TYPE (symbol), frame, data, size,
-				    dlbaton->per_cu);
+  val = dwarf2_evaluate_loc_desc (SYMBOL_TYPE (symbol), frame, data, size,
+				  dlbaton->per_cu);
 
   return val;
 }
@@ -3893,7 +3893,7 @@ loclist_tracepoint_var_ref (struct symbol *symbol, struct gdbarch *gdbarch,
   unsigned int addr_size = dwarf2_per_cu_addr_size (dlbaton->per_cu);
 
   data = dwarf2_find_location_expression (dlbaton, &size, ax->scope);
-  if (data == NULL || size == 0)
+  if (size == 0)
     value->optimized_out = 1;
   else
     dwarf2_compile_expr_to_ax (ax, value, gdbarch, addr_size, data, data + size,
diff --git a/gdb/dwarf2loc.h b/gdb/dwarf2loc.h
index 32aa0af..8196791 100644
--- a/gdb/dwarf2loc.h
+++ b/gdb/dwarf2loc.h
@@ -87,10 +87,12 @@ struct value *dwarf2_evaluate_loc_desc (struct type *type,
 
 struct dwarf2_locexpr_baton
 {
-  /* Pointer to the start of the location expression.  */
+  /* Pointer to the start of the location expression.  Valid only if SIZE is
+     not zero.  */
   const gdb_byte *data;
 
-  /* Length of the location expression.  */
+  /* Length of the location expression.  For optimized out expressions it is
+     zero.  */
   unsigned long size;
 
   /* The compilation unit containing the symbol whose location
diff --git a/gdb/dwarf2read.c b/gdb/dwarf2read.c
index 0b16ef8..5fa6c5b 100644
--- a/gdb/dwarf2read.c
+++ b/gdb/dwarf2read.c
@@ -722,6 +722,8 @@ struct function_range
 struct dwarf_block
   {
     unsigned int size;
+
+    /* Valid only if SIZE is not zero.  */
     gdb_byte *data;
   };
 
@@ -14217,7 +14219,6 @@ dwarf2_fetch_die_location_block (unsigned int offset,
     {
       /* DWARF: "If there is no such attribute, then there is no effect.".  */
 
-      retval.data = NULL;
       retval.size = 0;
     }
   else if (attr_form_is_section_offset (attr))
@@ -15495,7 +15496,6 @@ dwarf2_symbol_mark_computed (struct attribute *attr, struct symbol *sym,
 	  dwarf2_invalid_attrib_class_complaint ("location description",
 						 SYMBOL_NATURAL_NAME (sym));
 	  baton->size = 0;
-	  baton->data = NULL;
 	}
 
       SYMBOL_COMPUTED_OPS (sym) = &dwarf2_locexpr_funcs;
diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index 285f842..b06f870 100644
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,5 +1,15 @@
 2011-10-12  Jan Kratochvil  <jan.kratochvil@redhat.com>
 
+	Fix empty DWARF expressions DATA vs. SIZE conditionals.
+	* gdb.dwarf2/dw2-op-call.S (arraycallnoloc, arraynoloc): New DIEs.
+	(loclist): New.
+	(4): New abbrev.
+	* gdb.dwarf2/dw2-op-call.exp: Remove variable srcfile and executable.
+	Use prepare_for_testing, remove clean_restart.
+	(p arraynoloc, p arraycallnoloc): New tests.
+
+2011-10-12  Jan Kratochvil  <jan.kratochvil@redhat.com>
+
 	* gdb.cp/namespace-enum.exp (executable): New variable.
 	(binfile): Use ${objdir}/${subdir}/ prefix.
 	Use ${executable} for clean_restart.
diff --git a/gdb/testsuite/gdb.dwarf2/dw2-op-call.S b/gdb/testsuite/gdb.dwarf2/dw2-op-call.S
index 9a0efca..0db493e 100644
--- a/gdb/testsuite/gdb.dwarf2/dw2-op-call.S
+++ b/gdb/testsuite/gdb.dwarf2/dw2-op-call.S
@@ -72,10 +72,30 @@ array3:	.2byte	3
 	.uleb128	array3-array1		/*     <uconst> */
 2:
 
+	.uleb128	3			/* Abbrev: DW_TAG_variable */
+	.ascii		"arraycallnoloc\0"	/* DW_AT_name */
+	.4byte		.L2byte_type-.Lcu1_begin /* DW_AT_type */
+	.byte		2f - 1f			/* DW_AT_location */
+1:	.byte		0x99			/*   DW_OP_call4 */
+	.4byte		.Larraynoloc-.Lcu1_begin /*     <current CU offset> */
+2:
+
+.Larraynoloc:
+	.uleb128	4			/* Abbrev: DW_TAG_variable-loclist */
+	.ascii		"arraynoloc\0"		/* DW_AT_name */
+	.4byte		.L2byte_type-.Lcu1_begin /* DW_AT_type */
+	.4byte		loclist			/* DW_AT_location */
+
 	.byte		0			/* End of children of CU */
 
 .Lcu1_end:
 
+/* Location list.  */
+	.section	.debug_loc
+loclist:
+	/* Location list end.  */
+	.4byte	0, 0
+
 /* Abbrev table */
 	.section .debug_abbrev
 .Labbrev1_begin:
@@ -115,5 +135,17 @@ array3:	.2byte	3
 	.byte		0x0			/* Terminator */
 	.byte		0x0			/* Terminator */
 
+	.uleb128	4			/* Abbrev code */
+	.uleb128	0x34			/* DW_TAG_variable-loclist */
+	.byte		0			/* has_children */
+	.uleb128	0x3			/* DW_AT_name */
+	.uleb128	0x8			/* DW_FORM_string */
+	.uleb128	0x49			/* DW_AT_type */
+	.uleb128	0x13			/* DW_FORM_ref4 */
+	.uleb128	0x2			/* DW_AT_location */
+	.uleb128	0x06			/* DW_FORM_data4 */
+	.byte		0x0			/* Terminator */
+	.byte		0x0			/* Terminator */
+
 	.byte		0x0			/* Terminator */
 	.byte		0x0			/* Terminator */
diff --git a/gdb/testsuite/gdb.dwarf2/dw2-op-call.exp b/gdb/testsuite/gdb.dwarf2/dw2-op-call.exp
index 3319133..416eef4 100644
--- a/gdb/testsuite/gdb.dwarf2/dw2-op-call.exp
+++ b/gdb/testsuite/gdb.dwarf2/dw2-op-call.exp
@@ -22,18 +22,20 @@ if {![dwarf2_support]} {
 }
 
 set testfile "dw2-op-call"
-set srcfile ${testfile}.S
-set executable ${testfile}.x
-
-if  { [gdb_compile "${srcdir}/${subdir}/${srcfile}" "${objdir}/${subdir}/${executable}" object {nodebug}] != "" } {
+if { [prepare_for_testing ${testfile}.exp ${testfile} [list ${testfile}.S main.c] {nodebug}] } {
     return -1
 }
 
-clean_restart $executable
-
 # Additional test to verify the referenced CU is not aged out.
 gdb_test_no_output "maintenance set dwarf2 max-cache-age 0"
 
 gdb_test "p array1" " = 1"
 gdb_test "p array2" " = 2" "array2 using DW_OP_call2"
 gdb_test "p array3" " = 3" "array3 using DW_OP_call4"
+
+# Location lists need PC.
+if ![runto_main] {
+    return -1
+}
+gdb_test "p arraynoloc" " = <optimized out>"
+gdb_test "p arraycallnoloc" {Asked for position 0 of stack, stack only has 0 elements on it\.}