The unw_set_caching_policy() routine sets the caching policy of address space as to the policy specified by argument policy. The policy argument can take one of three possible values:
Turns off caching completely. This also implicitly flushes the contents of all caches as if unw_flush_cache() had been called.
Enables caching using a global cache that is shared by all threads. If global caching is unavailable or unsupported, libunwind may fall back on using a per-thread cache, as if UNW_CACHE_PER_THREAD had been specified.
Enables caching using thread-local caches. If a thread-local caching are unavailable or unsupported, libunwind may fall back on using a global cache, as if UNW_CACHE_GLOBAL had been specified.
If caching is enabled, an application must be prepared to make appropriate calls to unw_flush_cache() whenever the target changes in a way that could affect the validity of cached information. For example, after unloading (removing) a shared library, unw_flush_cache() would have to be called (at least) for the address-range that was covered by the shared library.
For address spaces created via unw_create_addr_space(3), caching is turned off by default. For the local address space unw_local_addr_space, caching is turned on by default.
On successful completion, unw_set_caching_policy() returns 0. Otherwise the negative value of one of the error-codes below is returned.
THREAD AND SIGNAL SAFETY
unw_set_caching_policy() is thread-safe but not safe to use from a signal handler.
The desired caching policy could not be established because the application is out of memory.