Nate Chandler 4dfaa77935 [IRGen] Pack extra data pattern structs. ...

Previously, the extra data pattern structs for struct and enums were not
packed.

On 32 bit, this resulted in an extra data pattern struct which was 4
bytes too large whenever there was an odd number of fields in the
struct.  The result was writing past the end of the allocated struct.
That bug only caused occasional crashes because (1) for the most part
there was additional space beyond the end of the allocation intended for
the struct metadata in the bump allocator and (2) while half of the
trailing flags field would be overwritten, because those bits of the
trailing flags being nonzero did not have an observable effect since
those bits of the trailing flags field are not yet used.

Here, the structs are marked packed, resulting in the appropriate size
for the extra data pattern structs on 32 bit platforms.

rdar://problem/68997282

2020-11-19 00:59:53 -08:00

34 KiB

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