tree 845b1cc0c0f366cce48e9f6b33896d9ed233723c
parent 2bbd33b33217ff4a73434ebf10cdac41e2ef5e34
author Veselin Georgiev <veselin.georgiev@garmin.com> 1532716389 -0500
committer Joshua Watt <Joshua.Watt@garmin.com> 1533045746 -0500

Fix SIGBUS due to unaligned access

Update RAPIDJSON_ALIGN() to always align on an 8-byte boundary
unless otherwise overridden.

On some platforms (such as ARM), 64-bit items (such as doubles and
64-bit integers) must be aligned to an 8 byte address, even though the
architecture is only 32-bits. On these platforms, MemoryPoolAllocator
must match the malloc() behavior and return a 8 byte aligned allocation.
This eliminates any alignment issues that may occur at the expense of
additional memory overhead.

Failure to do so caused a SIGBUS signal when calling
GenericValue::SetNull(). The size of the data_ member of the
GenericValue class is 16 bytes in 32-bit mode and its constructor
requires an 8-byte aligned access.

While parsing a JSON formatted string using Document::ParseStream(), a
stack object containing GenericValue items was constructed. Since the
stack was 8-byte aligned, the constructor calls would succeed. When the
lifetime of the object ends, SetObjectRaw() is invoked. This triggered
an allocation with 4-byte alignment to which the previously 8-byte
aligned GenericValue array was copied. After this, any call to a
GenericValue API that triggered the constructor and thus the placement
new operation on the Data type member would trigger a SIGBUS.

Signed-off-by: Veselin Georgiev <veselin.georgiev@garmin.com>
Signed-off-by: Joshua Watt <Joshua.Watt@garmin.com>