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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
Download Patch File Download Diff File Expand all files Collapse all files

12
gdb/gdbtypes.c
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@@ -901,7 +901,8 @@ operator== (const range_bounds &l, const range_bounds &r)
return (FIELD_EQ (low)
&& FIELD_EQ (high)
&& FIELD_EQ (flag_upper_bound_is_count)
&& FIELD_EQ (flag_bound_evaluated));
&& FIELD_EQ (flag_bound_evaluated)
&& FIELD_EQ (bias));
#undef FIELD_EQ
}
@@ -912,7 +913,8 @@ operator== (const range_bounds &l, const range_bounds &r)
struct type *
create_range_type (struct type *result_type, struct type *index_type,
const struct dynamic_prop *low_bound,
const struct dynamic_prop *high_bound)
const struct dynamic_prop *high_bound,
LONGEST bias)
{
/* The INDEX_TYPE should be a type capable of holding the upper and lower
bounds, as such a zero sized, or void type makes no sense. */
@@ -932,6 +934,7 @@ create_range_type (struct type *result_type, struct type *index_type,
TYPE_ZALLOC (result_type, sizeof (struct range_bounds));
TYPE_RANGE_DATA (result_type)->low = *low_bound;
TYPE_RANGE_DATA (result_type)->high = *high_bound;
TYPE_RANGE_DATA (result_type)->bias = bias;
if (low_bound->kind == PROP_CONST && low_bound->data.const_val >= 0)
TYPE_UNSIGNED (result_type) = 1;
@@ -968,7 +971,7 @@ create_static_range_type (struct type *result_type, struct type *index_type,
high.kind = PROP_CONST;
high.data.const_val = high_bound;
result_type = create_range_type (result_type, index_type, &low, &high);
result_type = create_range_type (result_type, index_type, &low, &high, 0);
return result_type;
}
@@ -2015,9 +2018,10 @@ resolve_dynamic_range (struct type *dyn_range_type,
static_target_type
= resolve_dynamic_type_internal (TYPE_TARGET_TYPE (dyn_range_type),
addr_stack, 0);
LONGEST bias = TYPE_RANGE_DATA (dyn_range_type)->bias;
static_range_type = create_range_type (copy_type (dyn_range_type),
static_target_type,
&low_bound, &high_bound);
&low_bound, &high_bound, bias);
TYPE_RANGE_DATA (static_range_type)->flag_bound_evaluated = 1;
return static_range_type;
}