Fix undefined sanitizer issue in compact_array

[MBkkt]

Also I think really correct code, should start with non zero capacity (so correct capacity can be seted in ctor)

[jmr]

Also I think really correct code, should start with non zero capacity (so correct capacity can be seted in ctor)

Why? Feel free to send another PR if you think there are more improvements.

[MBkkt]

Why? Feel free to send another PR if you think there are more improvements

Because we always have some capacity on "stack". Same as for sso string.

[jmr]

Because we always have some capacity on "stack". Same as for sso string.

I'm not sure what you mean. There's already inline SSO-like space allocated:

s2geometry/src/s2/util/gtl/compact_array.h

Line 127 in e15d00b

char inlined_elements_[3 - kUnusedPaddingBytes];

Send a PR to make it clear.

[MBkkt]

I mean sso string after default ctor have non zero capacity.
Why same not possible for this array?

[jmr]

Anything is possible. Send a PR if you think it can be improved.