This patch changes the 'Allocator' interface to the use of 'Attempt'
return values instead of using exceptions for propagating errors.
To largely uphold compatibility with components using the original
exception-based interface - in particluar use cases where an 'Allocator'
is passed to the 'new' operator - the traditional 'alloc' is still
supported. But it existes merely as a wrapper around the new
'try_alloc'.
Issue #4324
This patch untangles the interplay of the base library and the libc
during the exit handling.
- The CXA ABI for the atexit handling is now provided by the libc.
For plain Genode components without libc dependency, __cxa_atexit
is a no-op, which is consistent with Genode's notion of components.
- The 'abort' implementation of the base library no longer calls
'genode_exit' but merely 'sleep_forever'. This way, the cxx library
no longer depends on a 'genode_exit' implementation.
- The libc provides 'atexit' support by storing metadata on the
libc kernel's heap now, thereby eliminating the former bounded
maximum number of atexit handlers.
- Shared-library dtors are no longer called via the atexit mechanism
by explicitly by the dynamic linker. This slightly changes the
call order of destructors (adjustment of the ldso test). Functions
marked as destructors are called after the atexit handlers now.
- The libc executes atexit handlers in the application context,
which supports the I/O operations in those handles, in particular
the closing of file descriptors.
Fixes#3851
