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Handle bit offset and bit size in base types

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PR symtab/25470 points out that the Zig programming language allows
integers of various bit sizes (including zero), not just sizes that
are a multiple of 8.

This is supported in DWARF by applying both a byte size and a
DW_AT_bit_size.

This patch adds support for this feature to integer and boolean types.
Other base types are not handled -- for floating-point types, this
didn't seem to make sense, and for character types I didn't see much
need.  (These can be added later if desired.)

I've also added support for DW_AT_data_bit_offset at the same time.  I
don't know whether the Zig compiler requires this, but it was
described in the same section in the DWARF standard and was easy to
add.

A new test case is supplied, using the DWARF assembler.

gdb/ChangeLog
2020-09-23  Tom Tromey  <tom@tromey.com>

	PR symtab/25470:
	* value.c (unpack_long, pack_long, pack_unsigned_long): Handle bit
	offset and bit size.
	* printcmd.c (print_scalar_formatted): Handle zero-length
	integer.
	(print_scalar_formatted): Use bit_size_differs_p.
	* gdbtypes.h (enum type_specific_kind) <TYPE_SPECIFIC_INT>: New
	constant.
	(union type_specific): <int_stuff>: New member.
	(struct type) <bit_size_differs_p, bit_size, bit_offset>: New
	methods.
	* gdbtypes.c (init_integer_type, init_boolean_type): Initialize
	TYPE_SPECIFIC_FIELD.
	(recursive_dump_type, copy_type_recursive): Update.
	* dwarf2/read.c (read_base_type): Handle DW_AT_bit_size and
	DW_AT_data_bit_offset.

gdb/testsuite/ChangeLog
2020-09-23  Tom Tromey  <tom@tromey.com>

	* gdb.dwarf2/intbits.exp: New file.
	* gdb.dwarf2/intbits.c: New file.
This commit is contained in:
Tom Tromey 2020-09-23 09:39:24 -06:00
parent bac51ab78d
commit 20a5fcbd5b
9 changed files with 406 additions and 7 deletions
Download patch file Download diff file Expand all files Collapse all files

24
gdb/gdbtypes.c
View file

@ -3194,6 +3194,10 @@ init_integer_type (struct objfile *objfile,
if (unsigned_p)
t->set_is_unsigned (true);
TYPE_SPECIFIC_FIELD (t) = TYPE_SPECIFIC_INT;
TYPE_MAIN_TYPE (t)->type_specific.int_stuff.bit_size = bit;
TYPE_MAIN_TYPE (t)->type_specific.int_stuff.bit_offset = 0;
return t;
}
@ -3228,6 +3232,10 @@ init_boolean_type (struct objfile *objfile,
if (unsigned_p)
t->set_is_unsigned (true);
TYPE_SPECIFIC_FIELD (t) = TYPE_SPECIFIC_INT;
TYPE_MAIN_TYPE (t)->type_specific.int_stuff.bit_size = bit;
TYPE_MAIN_TYPE (t)->type_specific.int_stuff.bit_offset = 0;
return t;
}
@ -5188,6 +5196,16 @@ recursive_dump_type (struct type *type, int spaces)
gdb_print_host_address (TYPE_SELF_TYPE (type), gdb_stdout);
puts_filtered ("\n");
break;
case TYPE_SPECIFIC_INT:
if (type->bit_size_differs_p ())
{
unsigned bit_size = type->bit_size ();
unsigned bit_off = type->bit_offset ();
printfi_filtered (spaces, " bit size = %u, bit offset = %u\n",
bit_size, bit_off);
}
break;
}
if (spaces == 0)
@ -5411,6 +5429,12 @@ copy_type_recursive (struct objfile *objfile,
copy_type_recursive (objfile, TYPE_SELF_TYPE (type),
copied_types));
break;
case TYPE_SPECIFIC_INT:
TYPE_SPECIFIC_FIELD (new_type) = TYPE_SPECIFIC_INT;
TYPE_MAIN_TYPE (new_type)->type_specific.int_stuff
= TYPE_MAIN_TYPE (type)->type_specific.int_stuff;
break;
default:
gdb_assert_not_reached ("bad type_specific_kind");
}