This trick was pioneered in Linux as the config_enabled() macro. The
madness has the effect of taking a macro value that may be defined to
"1" (e.g. CONFIG_MYFEATURE), or may not be defined at all and turning
it into a literal expression that can be used at "runtime". That is,
it works similarly to "defined(CONFIG_MYFEATURE)" does except that it
is an expansion that can exist in a standard expression and be seen by
the compiler and optimizer. Thus much #ifdef usage can be replaced
with cleaner expressions like:
if (IS_ENABLED(CONFIG_MYFEATURE))
myfeature_enable();
Change-Id: I40657d2aa3f802429ac33675a1fe245a5da86615
Signed-off-by: Andy Ross <andrew.j.ross@intel.com>
5bc458a0fa