Fix: invalid alignment of enumeration fields

Issue
---

According to the CTF specification, the alignment of an enumeration is
that of its container integer field type. However, ctf-ir does not
forward the alignment of an enumeration field type's alignment in
bt_field_type_get_alignment().

This causes babeltrace to fail to read traces produced by lttng-ust
following a fix that causes it to generate extended event headers. The
problem is observed on ARM platforms since lttng-ust will produce
a layout that does not result in unaligned memory accesses.

Solution
---

The alignment of the enumeration field type's container is sampled
when the enumeration field type is frozen.

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>

diff --git a/lib/ctf-ir/field-types.c b/lib/ctf-ir/field-types.c
index c2a5383ccc86cb71f8d5f602c7cfee7dc46f2b41..be3e2d0f5c9c54f13690384a79e739c86ef15665 100644 (file)
--- a/lib/ctf-ir/field-types.c
+++ b/lib/ctf-ir/field-types.c
@@ -2997,6 +2997,15 @@ int bt_field_type_get_alignment(struct bt_field_type *type)
                ret = (int) type->alignment;
                break;
        }
+       case BT_FIELD_TYPE_ID_ENUM:
+       {
+               struct bt_field_type *container =
+                       bt_field_type_enumeration_get_container_type(type);
+
+               ret = bt_field_type_get_alignment(container);
+               bt_put(container);
+               break;
+       }
        case BT_FIELD_TYPE_ID_UNKNOWN:
                BT_LOGW("Invalid parameter: unknown field type ID: "
                        "addr=%p, ft-id=%d", type, type_id);
@@ -3725,6 +3734,7 @@ void bt_field_type_enumeration_freeze(struct bt_field_type *type)
                type, struct bt_field_type_enumeration, parent);
 
        BT_LOGD("Freezing enumeration field type object: addr=%p", type);
+       type->alignment = bt_field_type_get_alignment(type);
        set_enumeration_range_overlap(type);
        generic_field_type_freeze(type);
        BT_LOGD("Freezing enumeration field type object's container field type: int-ft-addr=%p",