libstdc++-v3/libsupc++/eh_tm.cc

   1 // -*- C++ -*- Exception handling routines for Transactional Memory.
   2 // Copyright (C) 2009-2023 Free Software Foundation, Inc.
   3 //
   4 // This file is part of GCC.
   5 //
   6 // GCC is free software; you can redistribute it and/or modify
   7 // it under the terms of the GNU General Public License as published by
   8 // the Free Software Foundation; either version 3, or (at your option)
   9 // any later version.
  10 //
  11 // GCC is distributed in the hope that it will be useful,
  12 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 // GNU General Public License for more details.
  15 //
  16 // Under Section 7 of GPL version 3, you are granted additional
  17 // permissions described in the GCC Runtime Library Exception, version
  18 // 3.1, as published by the Free Software Foundation.
  19
  20 // You should have received a copy of the GNU General Public License and
  21 // a copy of the GCC Runtime Library Exception along with this program;
  22 // see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  23 // <http://www.gnu.org/licenses/>.
  24
  25 #include <cstdlib>
  26 #include "unwind-cxx.h"
  27 #include "eh_atomics.h"
  28
  29 using namespace __cxxabiv1;
  30
  31 // Free one C++ exception.
  32
  33 static void
  34 free_any_cxa_exception (_Unwind_Exception *eo)
  35 {
  36   __cxa_refcounted_exception *h
  37     = __get_refcounted_exception_header_from_ue (eo);
  38
  39   if (__is_dependent_exception (eo->exception_class))
  40     {
  41       __cxa_dependent_exception *dep
  42         = __get_dependent_exception_from_ue (eo);
  43
  44       h = __get_refcounted_exception_header_from_obj (dep->primaryException);
  45
  46       __cxa_free_dependent_exception (dep);
  47     }
  48
  49   if (__gnu_cxx::__eh_atomic_dec (&h->referenceCount))
  50     __cxa_free_exception (h + 1);
  51 }
  52
  53 // Cleanup exception handling state while rolling back state for
  54 // a software transactional memory transaction.
  55 //
  56 // UNTHROWN_OBJ is non-null if we've called __cxa_allocate_exception
  57 // but not yet called __cxa_throw for it.
  58 //
  59 // CLEANUP_EXC is non-null if we're currently processing a cleanup
  60 // along an exception path, but we've not caught the exception yet.
  61 //
  62 // CAUGHT_COUNT is the nesting depth of __cxa_begin_catch within
  63 // the transaction; undo as if calling __cxa_end_catch that many times.
  64
  65 extern "C" void
  66 __cxxabiv1::__cxa_tm_cleanup (void *unthrown_obj,
  67                               void *cleanup_exc,
  68                               unsigned int caught_count) throw()
  69 {
  70   __cxa_eh_globals *globals = __cxa_get_globals_fast ();
  71
  72   // Handle a C++ exception not yet thrown.
  73   if (unthrown_obj)
  74     {
  75       globals->uncaughtExceptions -= 1;
  76       __cxa_free_exception (unthrown_obj);
  77     }
  78
  79   // Handle an exception not yet caught ie. processing a cleanup
  80   // in between the throw and the catch.
  81   if (cleanup_exc)
  82     {
  83       _Unwind_Exception *eo
  84         = reinterpret_cast <_Unwind_Exception *>(cleanup_exc);
  85       if (__is_gxx_exception_class (eo->exception_class))
  86         free_any_cxa_exception (eo);
  87       else
  88         _Unwind_DeleteException (eo);
  89     }
  90
  91   // Do __cxa_end_catch caught_count times, but don't bother running
  92   // the destructors for the objects involved.  All of that is being
  93   // undone by the transaction restart.
  94   if (caught_count > 0)
  95     {
  96       __cxa_exception *h = globals->caughtExceptions;
  97
  98       // Rethrown foreign exceptions are removed from the stack immediately.
  99       // We would have freed this exception via THIS_EXC above.
 100       if (h == NULL)
 101         return;
 102
 103       do
 104         {
 105           __cxa_exception *next;
 106           _Unwind_Exception *eo = &h->unwindHeader;
 107
 108           if (__is_gxx_exception_class (eo->exception_class))
 109             {
 110               next = h->nextException;
 111               free_any_cxa_exception (eo);
 112             }
 113           else
 114             {
 115               _Unwind_DeleteException (eo);
 116               next = 0;
 117             }
 118
 119           h = next;
 120         }
 121       while (--caught_count);
 122
 123       globals->caughtExceptions = h;
 124     }
 125 }