The #if predicate evaluates to false if the macro is undefined, or
defined to 0. #ifdef (and its synonym #if defined) evaluates to false
only if the macro is undefined.
The new setup allows differentiating between setting a macro to 0 (to
express that the capability definitely does not exist / should not be
used) and leaving a macro undefined (to express not knowing whether a
capability exists / not caring if a capability is used).
PiperOrigin-RevId: 391094241
This lets us remove main() from snappy_bench.cc and snappy_unittest.cc,
which simplifies integrating these tests and benchmarks with other
suites.
PiperOrigin-RevId: 347857427