r175949 - ubsan: Emit bounds checks for array indexing, vector indexing, and (in really simple cases) pointer arithmetic. This augments the existing bounds checking with language-level array bounds information.

[Sean Silva]

Will this trigger on the really common usage (in C) of a length-1
array as the last member of a struct? (I believe this is done for
compatibility with compilers before flexible array members were
introduced (C99)?).

-- Sean Silva