Since OpenBSD 6.4 (https://www.openbsd.org/64.html), the stack pointer
must point to MAP_STACK memory, or the kernel may kill the process
with a signal. All stack allocators must pass MAP_STACK to mmap(2).
Define BOOST_CONTEXT_USE_MAP_STACK on OpenBSD, and don't define it on
other systems. This doesn't check for old versions of OpenBSD without
MAP_STACK; but OpenBSD has stopped maintaining versions before 6.4.
If BOOST_CONTEXT_USE_MAP_STACK is defined, then cause the stack
allocators to pass MAP_STACK to mmap(2):
- fixedsize_stack uses mmap/munmap instead of malloc/free. This
comes from a patch in OpenBSD Ports.
- protected_fixedsize_stack adds MAP_STACK to the mmap flags (as it
does in OpenBSD Ports). Assume that systems with MAP_STACK also
have MAP_ANON; this is true on OpenBSD. Delete POSIX comment,
because I can't find MAP_ANON nor MAP_ANONYMOUS in POSIX, so these
mmap calls don't conform to POSIX.
- pooled_fixedsize_stack can't call munmap, because the pool's free
doesn't know the allocation's size. Instead use posix_memalign to
allocate memory, then mmap to replace the pages with MAP_STACK
pages, so the pool's free may call std::free.
OpenBSD has no <ucontext.h>, so edit test/Jamfile.v2 to skip ucontext
tests on OpenBSD.
This commit and https://github.com/boostorg/test/pull/231 causes
libs/context/test `b2 full` to pass on OpenBSD 6.5 for 64-bit x86.
`b2 fc` fails because the allocator in test_fcontext.cpp does not use
MAP_STACK. The tests seem not to cover pooled_fixedsize_stack nor
protected_fixedsize_stack, but they still pass when I temporarily hack
callcc to use those allocators instead of fixedsize_stack.
- fix a cast from void* to the wrong dynamic type. The code cast from
tuple<decay_t<Fn>>* -> void* -> tuple<Fn>, which worked when an rvalue
was passed to resume_with(), but broke if the function was passed
by lvalue-reference, because it resulted in a cast from Fn to Fn&.
- remove use of std::tuple - no need to instantiate it for every callable.
Signed-off-by: Damian Jarek <damian.jarek93@gmail.com>
A few tests designed to deliberately fail appeal to UB (undefined
behavior), but as the MSVC optimizer improves we will take advantage of
that to remove UB statements. In order for deliberate failures to occur,
the tests must have the optimizer turned off.
