Issue in dwarf2/expr.c

["Rohr, Stephan" <stephan.rohr@intel.com>]

Hi all,

I came across a bug in dwarf2/expr.c:177 in function  rw_pieced_value. when reading a pieced value described by DW_OP_piece or DW_OP_bit_piece.

      if (value_type (v) != value_enclosing_type (v))
                internal_error (__FILE__, __LINE__,
                                                _("Should not be able to create a lazy value with "
                                                  "an enclosing type"));

This check can easily be triggered when casting a variable with location described by DW_OP_piece or DW_OP_bit_piece.

A minimal reproducer can be found in gdb/testsuite/gdb.dwarf2/shortpiece.exp, e.g. casting s1 to an array type triggers the error

p (short []) s1

I currently struggle to understand the reasoning for this check. I could think of changing this to

if (TYPE_LENGTH(value_type (v)) > TYPE_LENGTH( value_enclosing_type (v)))
to support the cast operation.

But in general, I'm not sure why this check is needed at all.

I appreciate your feedback.


Best
stephan