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From: "shahab.vahedi at gmail dot com" <sourceware-bugzilla@sourceware.org>
To: gdb-prs@sourceware.org
Subject: [Bug gdb/28104] Incorrect extraction of boolean fields in target
 description "struct" data type
Date: Mon, 19 Jul 2021 14:41:44 +0000
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https://sourceware.org/bugzilla/show_bug.cgi?id=3D28104

--- Comment #1 from Shahab <shahab.vahedi at gmail dot com> ---
When printing the fields of a register that is of a custom struct type,
the "unpack_bits_as_long ()" function is used:

  do_val_print (...)
    cp_print_value_fields (...)
      value_field_bitfield (...)
        unpack_value_bitfield (...)
          unpack_bits_as_long (...)

This function may sign-extend the extracted field while returning it:
------------------ 8< ------------------
  val >>=3D lsbcount;

  if (...)
    {
      valmask =3D (((ULONGEST) 1) << bitsize) - 1;
      val &=3D valmask;
      if (!field_type->is_unsigned ())
          if (val & (valmask ^ (valmask >> 1)))
              val |=3D ~valmask;
    }

  return val;
------------------ >8 ------------------

lsbcount:   Number of lower bits to get rid of.
bitsize:    The bit length of the field to be extracted.
val:        The register value.
field_type: The type of field that is being handled.

While the logic here is correct, there is a problem when it is
handling "field_type"s of "boolean".  Those types are NOT marked
as "unsigned" and therefore they end up being sign extended.
Although this is not a problem for "false" (0), it definitely
causes trouble for "true".

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