[Bug ada/81361] New: Exceptions mishandled (_Unwind_Resume() can't return)

["simon at pushface dot org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81361

            Bug ID: 81361
           Summary: Exceptions mishandled (_Unwind_Resume() can't return)
           Product: gcc
           Version: 8.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: ada
          Assignee: unassigned at gcc dot gnu.org
          Reporter: simon at pushface dot org
  Target Milestone: ---
            Target: x64_64-apple-darwin15

This problem was absent in snapshot gcc-8-20170528 and is present in snapshot
gcc-8-20170702 (and in git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@250075).

The result of 'make check-acats' is

                === acats Summary ===
# of expected passes            2276
# of unexpected failures        44
*** FAILURES: c760010 c761006 cb4006a cb4008a cb4009a cxa4016 cxa4019 cxa4020 
c94008a c94008c c94008d c94020a c954016 c99004a cxa4005 cxa4008 cxa4009 
c95040d c954a01 c954a02 c97304b ca11d01 ca11d02 cb20003 cb20006 cb20007 cxf3a02
 c95022b c97204b c9a007a c9a009a c9a009c c9a009f c9a009g c9a009h c9a010a
c9a011a cb1010a cb41001 ce2202a cxb3010 cxb3011 cxb3012 cxg1003 

and most if not all are related to exception handling: the log says e.g.

,.,. C97204B ACATS 2.5 17-07-08 18:21:06
---- C97204B CHECK THAT TASKING_ERROR IS RAISED IF THE CALLED TASK IS
                ABORTED BEFORE THE CONDITIONAL ENTRY CALL IS EXECUTED.
Assertion failed: (_Unwind_Resume() can't return), function _Unwind_Resume,
file
/BuildRoot/Library/Caches/com.apple.xbs/Sources/libunwind/libunwind-35.3/src/UnwindLevel1.c,
line 320.

This happens with the standard test optimisation (-O2); -O1 is OK.