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Handle DW_AT_endianity on enumeration types

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A user found that gdb would not correctly print a field from an Ada
record using the scalar storage order feature.  We tracked this down
to a combination of problems.

First, GCC did not emit DW_AT_endianity on the enumeration type.
DWARF does not specify this, but it is an obvious and harmless
extension.  This was fixed in GCC recently:

    https://gcc.gnu.org/pipermail/gcc-patches/2024-January/642347.html
    https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=5d8b60effc7268448a94fbbbad923ab6871252cd

Second, GDB did not handle this attribute on enumeration types.  This
patch makes this change and adds a test case that will pass with the
patched GCC.

So far, the GCC patch isn't on the gcc-13 branch; but if it ever goes
in, the test case in this patch can be updated to reflect that.

Reviewed-By: Keith Seitz <keiths@redhat.com>
This commit is contained in:
Tom Tromey 2024-01-09 11:47:17 -07:00
parent 44acb01769
commit 7737b13364
3 changed files with 57 additions and 27 deletions
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66
gdb/dwarf2/read.c
View File

@ -13071,6 +13071,44 @@ process_structure_scope (struct die_info *die, struct dwarf2_cu *cu)
}
}
/* Read DW_AT_endianity from DIE and compute the byte order that
should be used. The CU's arch is used as the default. The result
is true if the returned arch differs from the default, and false if
they are the same. If provided, the out parameter BYTE_ORDER is
also set. */
static bool
die_byte_order (die_info *die, dwarf2_cu *cu, enum bfd_endian *byte_order)
{
gdbarch *arch = cu->per_objfile->objfile->arch ();
enum bfd_endian arch_order = gdbarch_byte_order (arch);
enum bfd_endian new_order = arch_order;
attribute *attr = dwarf2_attr (die, DW_AT_endianity, cu);
if (attr != nullptr && attr->form_is_constant ())
{
int endianity = attr->constant_value (0);
switch (endianity)
{
case DW_END_big:
new_order = BFD_ENDIAN_BIG;
break;
case DW_END_little:
new_order = BFD_ENDIAN_LITTLE;
break;
default:
complaint (_("DW_AT_endianity has unrecognized value %d"), endianity);
break;
}
}
if (byte_order != nullptr)
*byte_order = new_order;
return new_order != arch_order;
}
/* Assuming DIE is an enumeration type, and TYPE is its associated
type, update TYPE using some information only available in DIE's
children. In particular, the fields are computed. */
@ -13218,6 +13256,8 @@ read_enumeration_type (struct die_info *die, struct dwarf2_cu *cu)
type->set_is_declared_class (dwarf2_flag_true_p (die, DW_AT_enum_class, cu));
type->set_endianity_is_not_default (die_byte_order (die, cu, nullptr));
set_die_type (die, type, cu);
/* Finish the creation of this type by using the enum's children.
@ -15121,7 +15161,6 @@ read_base_type (struct die_info *die, struct dwarf2_cu *cu)
struct attribute *attr;
int encoding = 0, bits = 0;
const char *name;
gdbarch *arch;
attr = dwarf2_attr (die, DW_AT_encoding, cu);
if (attr != nullptr && attr->form_is_constant ())
@ -15133,27 +15172,8 @@ read_base_type (struct die_info *die, struct dwarf2_cu *cu)
if (!name)
complaint (_("DW_AT_name missing from DW_TAG_base_type"));
arch = objfile->arch ();
enum bfd_endian byte_order = gdbarch_byte_order (arch);
attr = dwarf2_attr (die, DW_AT_endianity, cu);
if (attr != nullptr && attr->form_is_constant ())
{
int endianity = attr->constant_value (0);
switch (endianity)
{
case DW_END_big:
byte_order = BFD_ENDIAN_BIG;
break;
case DW_END_little:
byte_order = BFD_ENDIAN_LITTLE;
break;
default:
complaint (_("DW_AT_endianity has unrecognized value %d"), endianity);
break;
}
}
enum bfd_endian byte_order;
bool not_default = die_byte_order (die, cu, &byte_order);
if ((encoding == DW_ATE_signed_fixed || encoding == DW_ATE_unsigned_fixed)
&& cu->lang () == language_ada
@ -15291,7 +15311,7 @@ read_base_type (struct die_info *die, struct dwarf2_cu *cu)
maybe_set_alignment (cu, die, type);
type->set_endianity_is_not_default (gdbarch_byte_order (arch) != byte_order);
type->set_endianity_is_not_default (not_default);
if (TYPE_SPECIFIC_FIELD (type) == TYPE_SPECIFIC_INT)
{

9
gdb/testsuite/gdb.ada/scalar_storage.exp
View File

@ -33,5 +33,10 @@ if {![runto "storage.adb:$bp_location"]} {
return
}
gdb_test "print V_LE" "= \\(value => 126, another_value => 12\\)"
gdb_test "print V_BE" "= \\(value => 126, another_value => 12\\)"
gdb_test "print V_LE" "= \\(value => 126, another_value => 12, color => green\\)"
# This requires a compiler fix that is in GCC 14.
if {[gcc_major_version] < 14} {
setup_kfail "DW_AT_endianity on enum types" *-*-*
}
gdb_test "print V_BE" "= \\(value => 126, another_value => 12, color => green\\)"

9
gdb/testsuite/gdb.ada/scalar_storage/storage.adb
View File

@ -20,14 +20,19 @@ procedure Storage is
subtype Some_Range is Natural range 0..127;
subtype Another_Range is Natural range 0..15;
type Colors is (Red, Green, Blue);
for Colors use (Red => 0, Green => 1, Blue => 2);
type Rec is record
Value : Some_Range;
Another_Value : Another_Range;
Color : Colors;
end record;
for Rec use record
Value at 0 range 0..6;
Another_Value at 0 range 7..10;
Color at 0 range 11..13;
end record;
type Rec_LE is new Rec;
@ -42,8 +47,8 @@ procedure Storage is
V_BE : Rec_BE;
begin
V_LE := (126, 12);
V_BE := (126, 12);
V_LE := (126, 12, Green);
V_BE := (126, 12, Green);
Do_Nothing (V_LE'Address); -- START
Do_Nothing (V_BE'Address);