UBSAN is supported since GCC 4.9, which unfortunately did not yet have
__has_attribute(). To work around, the __GCC4_has_attribute workaround
requires defining which compiler version supports the given attribute.
In the case of no_sanitize_undefined, it is the first version that
supports UBSAN, which is GCC 4.9.
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
Link: https://lkml.kernel.org/r/20200615231529.GA119644@google.com
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