Am 17.07.2019 um 01:30 schrieb Branko Čibej:
On 16.07.2019 23:18, Rainer Jung wrote:
I had some need for using APR_POOL_DEBUG today and ran into a
situation where pool lifetimes needed a hint using apr_pool_join().
That is all documented and fine, except that I was surprised to see,
that apr_pool_join() doesn't work unless the application itself is
also compiled with APR_POOL_DEBUG. I think that's not the intend, one
should be able to replace the apr library against a debug one during
lifetime.
So IMHO apr_pool_join() in apr has to be a noop function when
APR_POOL_DEBUG is not defined, so that the function call is contained
in the application.
Currently when the app is compiled without APR_POOL_DEBUG, then in
apr.h we only have
#if APR_POOL_DEBUG || defined(DOXYGEN)
...
#else /* APR_POOL_DEBUG or DOXYGEN */
#ifdef apr_pool_join
#undef apr_pool_join
#endif
#define apr_pool_join(a,b)
...
#endif /* APR_POOL_DEBUG or DOXYGEN */
so apr_pool_join() would be an empty macro.
Other pool debug functions seem to share the same fate:
- apr_pool_owner_set()
- apr_pool_find()
- apr_pool_num_bytes()
- apr_pool_lock()
- and as mentioned apr_pool_join()
Any opinion on whether we should introduce empty implementations
instead of empty macros for those all?
What should apr_pool_join and the other pool debugging functions do if
you're not debugging pools? They should be no-ops. So replacing them
with empty macros makes sense.
Or are you arguing that two libapr variants, one compiles with
APR_POOL_DEBUG and one without, should be ABI- compatible?
As far as I understand it, one should be able to replace the normal apr
library by a debug apr library at runtime and get pool debugging. There
should be no need to provide a apr debug compilation of the app itself.
If an app needs calls to apr_pool_join() to guide the debugging, they
must be in the source code of the app and must not get compiled out.
No-op would only be OK, if the app they are function calls to no-op
functions, but not if they get compiled out.
So yes, I think it must be ABI compatible and except for the above 5
functions it is.
Regards,
Rainer
