On Mon, Mar 12, 2007 at 04:18:40PM -0400, John Baldwin wrote: > On Monday 12 March 2007 16:03, Pawel Jakub Dawidek wrote: > > On Mon, Mar 12, 2007 at 03:35:21PM -0400, John Baldwin wrote: > > > On Monday 12 March 2007 14:56, Pawel Jakub Dawidek wrote: > > > > On Mon, Mar 12, 2007 at 11:16:23AM -0400, John Baldwin wrote: > > > > > On Saturday 10 March 2007 15:52, Pawel Jakub Dawidek wrote: > > > > > > What about something like this: > > > > > > > > > > > > #define cv_wait(cv, lock) do { > > > > > > switch (LO_CLASSINDEX((struct lock_object *)(lock))) { > > > > > > > > > > The problem with a cast is you use type checking. Might as well do > this: > > > > > > > > > > #define cv_wait(cv, lock) _cv_wait((cv), (struct > > > > > lock_object *)(lock)) > > > > > > > > This will skip type checking and my version only cast to provide type > > > > checking, so when you pass some random variable it will give you an > > > > error. > > > > > > Not really, you may pass some garbage and the LO_CLASSINDEX turns out to > be a > > > mutex. :) You only get a runtime error, not a compile-time one. > > > Type-checking by the compiler is nice because you get compile-time errors. > > > > I'll get compile-time error, because cv_wait_mtx() takes > > 'struct condvar *' and 'struct mtx *' as arguments. So even if some > > garbage returns 1, which turns out to be a mutex, call to cv_wait_mtx() > > will generate compile-time error. > > Err, no, actually, yours will always give compile errors actually. Keep in > mind that LO_CLASSINDEX() is a run-time check. This: > > #define cv_wait(cv, lock) do { > switch (LO_CLASSINDEX((struct lock_object *)(lock))) { > case 1: > cv_wait_mtx(cv, lock); > break; > case 2: > cv_wait_sx(cv, lock); > break; > case 3: > cv_wait_rw(cv, lock); > break; > default: > panic("Invalid lock."); > } > } while (0) > > Will try to pass 'lock' to three different functions, at least 2 of which > will > trigger compile errors. :) The kernel won't choose which one to run until > runtime though. The key is that I want a compile error, not a panic(). :)
Ah, you are right. -- Pawel Jakub Dawidek http://www.wheel.pl [EMAIL PROTECTED] http://www.FreeBSD.org FreeBSD committer Am I Evil? Yes, I Am!
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