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Handle biased types

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In Ada, the programmer can request that a range type with a non-zero
base be stored in the minimal number of bits required for the range.
This is done by biasing the values; so, for example, a range of -7..-4
may be stored as two bits with a bias of -7.

This patch implements this for gdb.  It is done by adding a bias to
struct range_bounds and then adjusting a few spots to handle this.

The test case is written to use -fgnat-encodings=minimal, but a future
compiler patch will change the compiler to emit DW_AT_GNU_bias with
-fgnat-encodings=gdb.  It seemed good to get the gdb patch in first.

Tested on x86-64 Fedora 29; plus a variety of targets using AdaCore's
internal test suite.

gdb/ChangeLog
2019-09-03  Tom Tromey  <tromey@adacore.com>

	* ada-valprint.c (ada_val_print_num): Don't recurse for range
	types.
	(has_negatives): Unbias a range type bound.
	* dwarf2read.c (read_subrange_type): Handle DW_AT_GNU_bias.
	* gdbtypes.c (operator==): Handle new field.
	(create_range_type): Add "bias" parameter.
	(create_static_range_type, resolve_dynamic_range): Update.
	* gdbtypes.h (struct range_bounds) <bias>: New member.
	(create_range_type): Add bias parameter.
	* printcmd.c (print_scalar_formatted): Unbias range types.
	* value.c (unpack_long): Unbias range types.
	(pack_long): Bias range types.

gdb/testsuite/ChangeLog
2019-09-03  Tom Tromey  <tromey@adacore.com>

	* gdb.ada/bias.exp: New file.
	* gdb.ada/bias/bias.adb: New file.
	* gdb.ada/print_chars.exp: Add regression test.
	* gdb.ada/print_chars/foo.adb (My_Character): New type.
	(MC): New variable.
This commit is contained in:
Tom Tromey
2019-05-13 13:21:48 -06:00
parent f44b758d31
commit 4e962e74e4
15 changed files with 250 additions and 33 deletions
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48
gdb/printcmd.c
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@@ -405,21 +405,30 @@ print_scalar_formatted (const gdb_byte *valaddr, struct type *type,
/* Historically gdb has printed floats by first casting them to a
long, and then printing the long. PR cli/16242 suggests changing
this to using C-style hex float format. */
gdb::byte_vector converted_float_bytes;
if (TYPE_CODE (type) == TYPE_CODE_FLT
&& (options->format == 'o'
|| options->format == 'x'
|| options->format == 't'
|| options->format == 'z'
|| options->format == 'd'
|| options->format == 'u'))
this to using C-style hex float format.
Biased range types must also be unbiased here; the unbiasing is
done by unpack_long. */
gdb::byte_vector converted_bytes;
/* Some cases below will unpack the value again. In the biased
range case, we want to avoid this, so we store the unpacked value
here for possible use later. */
gdb::optional<LONGEST> val_long;
if ((TYPE_CODE (type) == TYPE_CODE_FLT
&& (options->format == 'o'
|| options->format == 'x'
|| options->format == 't'
|| options->format == 'z'
|| options->format == 'd'
|| options->format == 'u'))
|| (TYPE_CODE (type) == TYPE_CODE_RANGE
&& TYPE_RANGE_DATA (type)->bias != 0))
{
LONGEST val_long = unpack_long (type, valaddr);
converted_float_bytes.resize (TYPE_LENGTH (type));
store_signed_integer (converted_float_bytes.data (), TYPE_LENGTH (type),
byte_order, val_long);
valaddr = converted_float_bytes.data ();
val_long.emplace (unpack_long (type, valaddr));
converted_bytes.resize (TYPE_LENGTH (type));
store_signed_integer (converted_bytes.data (), TYPE_LENGTH (type),
byte_order, *val_long);
valaddr = converted_bytes.data ();
}
/* Printing a non-float type as 'f' will interpret the data as if it were
@@ -469,7 +478,8 @@ print_scalar_formatted (const gdb_byte *valaddr, struct type *type,
{
struct value_print_options opts = *options;
LONGEST val_long = unpack_long (type, valaddr);
if (!val_long.has_value ())
val_long.emplace (unpack_long (type, valaddr));
opts.format = 0;
if (TYPE_UNSIGNED (type))
@@ -477,15 +487,15 @@ print_scalar_formatted (const gdb_byte *valaddr, struct type *type,
else
type = builtin_type (gdbarch)->builtin_true_char;
value_print (value_from_longest (type, val_long), stream, &opts);
value_print (value_from_longest (type, *val_long), stream, &opts);
}
break;
case 'a':
{
CORE_ADDR addr = unpack_pointer (type, valaddr);
print_address (gdbarch, addr, stream);
if (!val_long.has_value ())
val_long.emplace (unpack_long (type, valaddr));
print_address (gdbarch, *val_long, stream);
}
break;