PASSERT() - asserting for panics

[Matthew Dillon]

:	PASSERT("foo", panic("foo"));
:
:The patch is at http://www.FreeBSD.org/~jhb/patches/passert.patch and below:
:..

    The general problem with creating a more complex style of assertion
    is, well, that it is more complex.  As a programmer who adds assertions
    all over the place (HAMMER has 343 KKASSERTs, for example), the last
    thing I want to do is to have to think about the assertion line itself
    or have to read through the visual pollution.  Most of the time I just
    want to KKASSERT(condition) and be done with it.

    I would consider using a DATASET (easily embedded in a statement as it
    is a static declaration) to back the assertion macro and then simplify
    it to just:

	PASSERT(label, condition)

    The kernel would collect the DATASETs together and provide a sysctl
    API to allow the action taken to be managed at run-time based on the
    label.  You could even have a version that doesn't use a label at all
    and is instead indexed by file and line.  The output would be the
    stringtized condition (similar to libc's assert(cond) or DFly's
    KKASSERT(cond)).  You could also have an optional macro to specify
    a default action for the label, and a master global sysctl to override
    everything.

    The actual code generated would simply be the conditional and, say,
    a call to _passert(&dataset), reducing code pollution as well as visual
    pollution.  I have considered doing something similar in DragonFly for
    KKASSERT to reduce the code generated by the multi-argument panic()
    it calls.

						-Matt