Twenty-eight programs built twice -- once plain, once sanitized -- and
compared on output and exit status, plus two positive controls that are
the only reason a clean result means anything: an out-of-bounds read
that must report, and a shift by the width of the type that must not,
because UBSan cannot see hand-written IR and this file would otherwise
be claiming coverage it does not have.
Its own alias rather than dune test. A sanitized program is a statically
linked 1.8MB binary and takes tens of seconds to link; the sweep is nine
minutes against the existing suite's seconds, and a test nobody will
wait for is a test nobody runs. dune build --root . @sanitize.
The checked sweep is clean. The unchecked variant -- ASan alone, with
Flan's own bounds checks off -- catches three of bounds.flan's six
deliberate out-of-bounds cases and is listed with why for the other
three: a global has a right redzone and nothing to its left, so arr[-1]
is invisible; a read past a string constant folds away entirely at -O2
and is caught only at -O0; and a reversed slice reads nothing at all.
ASan is not a substitute for the bounds checks, and now there is a table
saying which half it covers.
Joseph Ferano
c41c5812a9