On Wed, Sep 19, 2001 at 12:16:24PM -0700, Ryan Bloom wrote:
> On Wednesday 19 September 2001 11:37 am, William A. Rowe, Jr. wrote:
> > From: "Greg Stein" <[EMAIL PROTECTED]>
> > Sent: Wednesday, September 19, 2001 1:26 PM
> >
> > > On Wed, Sep 19, 2001 at 01:52:12PM -0400, Rodent of Unusual Size wrote:
> > > > Greg Stein wrote:
> > > > > It isn't a bug. Cleanups are for just wrapping things up,
> > > > > not doing work.
> > > >
> > > > If that's the authoritative answer, then we need to provide
> > > > a supported way for 'doing work' at cleanup time.
> > > >
> > > > > You might not even be able to open and use that file if
> > > > > your pool is n the process of being destroyed.
> > > >
> > > > That sounds like utter tripe. If you can't depend on the
> > > > pool lasting at least until your cleanup routine ends,
> > > > then the whole cleanup mechanism is seriously borked. AFAIK
> > > > it isn't, so I think the above assertion *is*.
> > >
> > > The problem is cross-dependency between the cleanup actions. One can
> > > destroy something another cleanup needs. If you restrict their actions to
> > > "simple" things, then the cross-dependencies are (hopefully!) removed.
> >
> > Really? No. Cleanups are run as a LIFO stack. Anything that existed when
> > something was added to the pool must exist when that something is removed
> > from the pool.
> >
> > IMHO, we need to make subpool scrubbing an actual LIFO cleanup as well, so
> > that will also be true of subpools.
> >
> > Considering how we use pools for dynamic libraries and the rest, it's
> > absolutely vital that they are unspun from the pool in LIFO order of their
> > creation.
>
> I agree with Bill. Having reviewed the code quite deeply yesterday, pool
> cleanups follow a very clean rule, and registering a cleanup from within
> a cleanup will always work if done correctly. If you have data in a pool
BZzzzt. The attached code registers a cleanup from within a cleanup, and
does so 'correctly'. See the program attached at the bottom, which behaves
incorrectly. It is simple code, but not knowing that a given
function registers a cleanup can cause major problems (leaking
file descriptors, etc. eventually). The file should contain 'Cleanup',
because the cleanup of the file should flush the buffer -- that
cleanup is never run, though.
> when the cleanup is registered, it is gauranteed to be there when the cleanup
> is run.
>
> Anything else is completely broken.
#include "apr.h"
#include "apr_file_io.h"
static apr_status_t my_cleanup(void *cbdata){
apr_pool_t *p = cbdata;
apr_file_t *file;
apr_file_open(&file, "/tmp/bonk",
APR_WRITE | APR_CREATE | APR_TRUNCATE | APR_BUFFERED,
APR_OS_DEFAULT, p);
apr_file_printf(file, "Cleanup");
return APR_SUCCESS;
}
int main(int argc, char *argv[]){
apr_pool_t *pool;
apr_initialize();
apr_pool_create(&pool, NULL);
apr_pool_cleanup_register(pool, pool, my_cleanup, NULL);
apr_pool_destroy(pool);
apr_terminate();
return 0;
}
