(Note I am also applying this to main and stable/13, to restore the old
libcxxrt ABI and to avoid having to maintain a compat library.)
After the recent cherry-picking of libcxxrt commits 0ee0dbfb0d and
d2b3fadf2d, users reported that editors/libreoffice packages from the
official package builders did not start anymore. It turns out that the
combination of these commits subtly changes the ABI, requiring all
applications that depend on internal details of struct _Unwind_Exception
(available via unwind-arm.h and unwind-itanium.h) to be recompiled.
However, the FreeBSD package builders always use -RELEASE jails, so
these still use the old declaration of struct _Unwind_Exception, which
is not entirely compatible. In particular, LibreOffice uses this struct
in its internal "uno bridge" component, where it attempts to setup its
own exception handling mechanism.
To fix this incompatibility, go back to the old declarations of struct
_Unwind_Exception, and restore the __LP64__ specific workaround we had
in place before (which was to cope with yet another, older ABI bug).
Effectively, this reverts upstream libcxxrt commits 88bdf6b290da
("Specify double-word alignment for ARM unwind") and b96169641f79
("Updated Itanium unwind"), and reapplies our commit 3c4fd2463b
("libcxxrt: add padding in __cxa_allocate_* to fix alignment").
PR: 253840
In 0ee0dbfb0d I imported a more recent
libcxxrt snapshot, which includes an upstream fix for the padding of
struct _Unwind_Exception:
e458560b7e
However, we also had a similar fix in our tree as:
https://cgit.freebsd.org/src/commit/?id=3c4fd2463bb29f65ef1404011fcb31e508cdf2e2
Since having both fixes makes the struct too large again, it leads to
SIGBUSes when throwing exceptions on amd64 (or other LP64 arches). This
is most easily tested by running kyua without any arguments.
It looks like our fix is no longer needed now, so revert it to reduce
diffs against upstream.
PR: 253226
Reviewed by: arichardson, kp
MFC after: 3 days
Differential Revision: https://reviews.freebsd.org/D28799
The addition of the referenceCount to __cxa_allocate_exception put the
unwindHeader at offset 0x58 in __cxa_exception, but it requires 16-byte
alignment. In order to avoid changing the current __cxa_exception ABI
(and thus breaking its consumers), add explicit padding in the
allocation routines (and account for it when freeing).
This is intended as a lower-risk change for FreeBSD 11. A "more correct"
fix should be prepared for upstream and -CURRENT.
Reviewed by: dim
MFC after: 3 days
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D7271
Interesting fixes:
3adaa2e Fix _Unwind_Exception cleanup functions
286776c Check exception cleanup function ptr before calling
edda626 Correct exception specifications on new and delete operators
* Don't call the _fast version of the TLS accessor in terminate() or
unexpected().
1) TLS may not have been set up yet.
2) When we're in one of these functions, Really Bad Stuff has
happened and potentially saving a few cycles really isn't
important.
* Merge in fixes from FreeBSD trunk to make atomics work with recent
clang.
MFC after: 1 week
an exception when you haven't caught one. This is largely a cosmetic fix, as
(unless you have a very unusual terminate handler installed) it will print a
nice error and then abort, rather than just aborting.
MFC after: 7 days
- Don't treat pointers to members as pointers in catch blocks (they're usually
fat pointers).
- Correctly catch foreign exceptions in catchalls.
- Ensure that a happens-before relationship is established when setting
terminate handlers in one thread and calling them in another.
MK_LIBCPLUSPLUS=yes to enable). This is a work-in-progress. It works for
me, but is not guaranteed to work for anyone else and may eat your dog.
To build C++ using libc++, add -stdlib=libc++ to your CXX and LD flags.
Bug reports welcome, bug fixes even more welcome...
Approved by: dim (mentor)
