Allow DW_OP_GNU_uninit in dwarf_expr_require_composition

In DWARF expression handling, some operators are required to be either
at the end of an expression or followed by a composition operator.  So
far only the operators DW_OP_reg0-31 were allowed to be followed by
DW_OP_GNU_uninit instead, and particularly DW_OP_regx was not, which is
obviously inconsistent.

This patch allows DW_OP_GNU_uninit after all operators requiring a
composition, to simplify the code and make it more consistent.  This
policy may be more permissive than necessary, but in the worst case just
leads to a DWARF location description resulting in an uninitialized
value instead of an error message.

gdb/ChangeLog:

	* dwarf2expr.c (dwarf_expr_require_composition): Allow
	DW_OP_GNU_uninit.
	(execute_stack_op): Use dwarf_expr_require_composition instead of
	copying its logic.

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 357f648..eaef0b0 100644 (file)
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,10 @@
+2016-10-05  Andreas Arnez  <arnez@linux.vnet.ibm.com>
+
+       * dwarf2expr.c (dwarf_expr_require_composition): Allow
+       DW_OP_GNU_uninit.
+       (execute_stack_op): Use dwarf_expr_require_composition instead of
+       copying its logic.
+
 2016-10-05  Anton Kolesov  <anton.kolesov@synopsys.com>
 
        arc-tdep.c (arc_frame_prev_register): Remove annoying log message.

diff --git a/gdb/dwarf2expr.c b/gdb/dwarf2expr.c
index 7eb1982..90e4e25 100644 (file)
--- a/gdb/dwarf2expr.c
+++ b/gdb/dwarf2expr.c
@@ -401,16 +401,15 @@ safe_skip_leb128 (const gdb_byte *buf, const gdb_byte *buf_end)
 \f
 
 /* Check that the current operator is either at the end of an
-   expression, or that it is followed by a composition operator.  */
+   expression, or that it is followed by a composition operator or by
+   DW_OP_GNU_uninit (which should terminate the expression).  */
 
 void
 dwarf_expr_require_composition (const gdb_byte *op_ptr, const gdb_byte *op_end,
                                const char *op_name)
 {
-  /* It seems like DW_OP_GNU_uninit should be handled here.  However,
-     it doesn't seem to make sense for DW_OP_*_value, and it was not
-     checked at the other place that this function is called.  */
-  if (op_ptr != op_end && *op_ptr != DW_OP_piece && *op_ptr != DW_OP_bit_piece)
+  if (op_ptr != op_end && *op_ptr != DW_OP_piece && *op_ptr != DW_OP_bit_piece
+      && *op_ptr != DW_OP_GNU_uninit)
     error (_("DWARF-2 expression error: `%s' operations must be "
             "used either alone or in conjunction with DW_OP_piece "
             "or DW_OP_bit_piece."),
@@ -818,13 +817,7 @@ execute_stack_op (struct dwarf_expr_context *ctx,
        case DW_OP_reg29:
        case DW_OP_reg30:
        case DW_OP_reg31:
-         if (op_ptr != op_end 
-             && *op_ptr != DW_OP_piece
-             && *op_ptr != DW_OP_bit_piece
-             && *op_ptr != DW_OP_GNU_uninit)
-           error (_("DWARF-2 expression error: DW_OP_reg operations must be "
-                    "used either alone or in conjunction with DW_OP_piece "
-                    "or DW_OP_bit_piece."));
+         dwarf_expr_require_composition (op_ptr, op_end, "DW_OP_reg");
 
          result = op - DW_OP_reg0;
          result_val = value_from_ulongest (address_type, result);