Using ASSERT

Using ASSERT

The assert() macro is familiar to many C programmers; it terminates a program with a message if its argument evaluates to false (see the assert(3X) reference page). This normal assert() macro does not work in a kernel module because the normal C library is not available. However, a similar function is available as the ASSERT() macro in the header file sys/debug.h.

The ASSERT() macro compiles to null code unless the compiler variable DEBUG is not only defined, but defined as YES. When it compiles to executable code, ASSERT() tests its argument. If the argument evaluates to false, a kernel panic is forced.

Clearly ASSERT() must be used with care, testing conditions that are truly essential to the integrity of the system. When reporting conditions that are merely operational errors, use a call to cmn_err() with the CE_WARN option.