From 440ea08bbf4c81f97852785642c6a6f18bdd28a9 Mon Sep 17 00:00:00 2001
From: Shahab Vahedi <shahab@synopsys.com>
Date: Mon, 19 Jul 2021 16:13:47 +0200
Subject: [PATCH 19/20] gdb: Make the builtin "boolean" type an unsigned type

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:

    val >>= lsbcount;

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

    return val;

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".

This patch constructs the builtin boolean type as such that it is
marked as an "unsigned" entity.

The issue tackled here was first encountered for arc-elf32 target
running on an x86_64 machine.  The unit-test introduced in this change
has passed for all the targets (--enable-targets=all) running on the
same x86_64 host.

Fixes: https://sourceware.org/PR28104

Will be a part of GDB 11:
https://sourceware.org/git?p=binutils-gdb.git;a=commit;h=91254b918f1b35359d44b567a15013c42a931460
---
 gdb/cp-valprint.c |   68 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 gdb/gdbtypes.c    |    2 -
 2 files changed, 69 insertions(+), 1 deletion(-)

--- a/gdb/cp-valprint.c
+++ b/gdb/cp-valprint.c
@@ -38,6 +38,8 @@
 #include "gdbsupport/byte-vector.h"
 #include "gdbarch.h"
 #include "cli/cli-style.h"
+#include "gdbsupport/selftest.h"
+#include "selftest-arch.h"
 
 static struct obstack dont_print_vb_obstack;
 static struct obstack dont_print_statmem_obstack;
@@ -721,11 +723,77 @@
     fprintf_filtered (stream, "%ld", (long) val);
 }
 
+#if GDB_SELF_TEST
+
+/* Test printing of TYPE_CODE_STRUCT values.  */
+
+static void
+test_print_fields (gdbarch *arch)
+{
+  struct field *f;
+  type *uint8_type = builtin_type (arch)->builtin_uint8;
+  type *bool_type = builtin_type (arch)->builtin_bool;
+  type *the_struct = arch_composite_type (arch, NULL, TYPE_CODE_STRUCT);
+  TYPE_LENGTH (the_struct) = 4;
+
+  /* Value:  1110 1001
+     Fields: C-BB B-A- */
+  if (gdbarch_byte_order (arch) == BFD_ENDIAN_LITTLE)
+    {
+      f = append_composite_type_field_raw (the_struct, "A", bool_type);
+      SET_FIELD_BITPOS (*f, 1);
+      FIELD_BITSIZE (*f) = 1;
+      f = append_composite_type_field_raw (the_struct, "B", uint8_type);
+      SET_FIELD_BITPOS (*f, 3);
+      FIELD_BITSIZE (*f) = 3;
+      f = append_composite_type_field_raw (the_struct, "C", bool_type);
+      SET_FIELD_BITPOS (*f, 7);
+      FIELD_BITSIZE (*f) = 1;
+    }
+  /* According to the logic commented in "make_gdb_type_struct ()" of
+   * target-descriptions.c, bit positions are numbered differently for
+   * little and big endians.  */
+  else
+    {
+      f = append_composite_type_field_raw (the_struct, "A", bool_type);
+      SET_FIELD_BITPOS (*f, 30);
+      FIELD_BITSIZE (*f) = 1;
+      f = append_composite_type_field_raw (the_struct, "B", uint8_type);
+      SET_FIELD_BITPOS (*f, 26);
+      FIELD_BITSIZE (*f) = 3;
+      f = append_composite_type_field_raw (the_struct, "C", bool_type);
+      SET_FIELD_BITPOS (*f, 24);
+      FIELD_BITSIZE (*f) = 1;
+    }
+
+  value *val = allocate_value (the_struct);
+  gdb_byte *contents = value_contents_writeable (val);
+  store_unsigned_integer (contents, TYPE_LENGTH (value_enclosing_type (val)),
+			  gdbarch_byte_order (arch), 0xe9);
+
+  string_file out;
+  struct value_print_options opts;
+  get_no_prettyformat_print_options (&opts);
+  cp_print_value_fields(val, &out, 0, &opts, NULL, 0);
+  SELF_CHECK (out.string () == "{A = false, B = 5, C = true}");
+
+  out.clear();
+  opts.format = 'x';
+  cp_print_value_fields(val, &out, 0, &opts, NULL, 0);
+  SELF_CHECK (out.string () == "{A = 0x0, B = 0x5, C = 0x1}");
+}
+
+#endif
+
 
 void _initialize_cp_valprint ();
 void
 _initialize_cp_valprint ()
 {
+#if GDB_SELF_TEST
+  selftests::register_test_foreach_arch ("print-fields", test_print_fields);
+#endif
+
   obstack_begin (&dont_print_stat_array_obstack,
 		 32 * sizeof (struct type *));
   obstack_begin (&dont_print_statmem_obstack,
--- a/gdb/gdbtypes.c
+++ b/gdb/gdbtypes.c
@@ -5854,7 +5854,7 @@
   builtin_type->builtin_string
     = arch_type (gdbarch, TYPE_CODE_STRING, TARGET_CHAR_BIT, "string");
   builtin_type->builtin_bool
-    = arch_type (gdbarch, TYPE_CODE_BOOL, TARGET_CHAR_BIT, "bool");
+    = arch_boolean_type (gdbarch, TARGET_CHAR_BIT, 1, "bool");
 
   /* The following three are about decimal floating point types, which
      are 32-bits, 64-bits and 128-bits respectively.  */