89ce327266
Some POSIX threads implementations (e.g. FreeBSD's libthr) allocate memory on the heap when pthread_rwlock_init() is called. Every call to that function must be accompanied by a corresponding call to pthread_rwlock_destroy() or else the memory allocated for the rwlock will leak. jemalloc can be used for detecting memory allocations which are not released by a process when it exits. Unfortunately, since jemalloc is also the system allocator on FreeBSD and a special (profiling-enabled) build of jemalloc is required for memory leak detection, this method cannot be used for detecting leaked memory allocated by libthr on a stock FreeBSD installation. However, libthr's behavior can be emulated on any platform by implementing alternative versions of libisc functions for creating and destroying rwlocks that allocate memory using malloc() and release it using free(). This enables using jemalloc for detecting missing pthread_rwlock_destroy() calls on any platform on which it works reliably. When the newly introduced ISC_TRACK_PTHREADS_OBJECTS preprocessor macro is set (and --enable-pthread-rwlock is used), allocate isc_rwlock_t structures on the heap in isc_rwlock_init() and free them in isc_rwlock_destroy(). Reuse existing functions defined in lib/isc/rwlock.c for other operations, but rename them first, so that they contain triple underscores (to indicate that these functions are implementation-specific, unlike their mutex and condition variable counterparts, which always use the pthreads implementation). Define the isc__rwlock_init() macro so that it is a logical counterpart of isc__mutex_init() and isc__condition_init(); adjust isc___rwlock_init() accordingly. Remove a redundant function prototype for isc__rwlock_lock() and rename that (static) function to rwlock_lock() in order to avoid having to use quadruple underscores.
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