[PATCH] Fix __cxa_exception ABI breakage in 4.4 (PR libstdc++/38732)
Jakub Jelinek
jakub@redhat.com
Wed Jan 7 16:23:00 GMT 2009
Hi!
As discussed in the PR, OpenOffice.org wants to get at current exception's
type, but as it needs to support pre-4.4 libstdc++ (and was written
in the pre-exception_ptr era), instead of using current_exception()
it copies part of unwind-cxx.h header (which isn't installed) and
uses __cxa_get_globals() to get at it.
In 4.4 referenceCount field was added, which changes the layout of
the __cxa_exception structure. As __cxa_exception layout is
part of C++ ABI, I think what OO.o does is something we should support.
The following patch fixes it by removing referenceCount from __cxa_exception
(so that it is layed out as before) and using a new struct with
__cxa_exception as last member for the referenceCount. As long as
the __cxa_exception in the new struct is not followed by padding
(given that one of the __cxa_exception fields is __attribute__((aligned))
I think it won't happen and we rely on it already for the unwind header
anyway), apps using the C++ ABI described __cxa_exception will continue
working.
Bootstrapped/regtested on x86_64-linux, ok for trunk?
2009-01-07 Jakub Jelinek <jakub@redhat.com>
PR libstdc++/38732
* libsupc++/unwind-cxx.h (__cxxabiv1::__cxa_exception): Remove
referenceCount field again.
(__cxxabiv1::__cxa_refcounted_exception): New struct.
(__cxxabiv1::__get_refcounted_exception_header_from_obj,
__cxxabiv1::__get_refcounted_exception_header_from_ue): New static
inline functions.
* libsupc++/eh_alloc.cc (__cxxabiv1::__cxa_allocate_exception,
__cxxabiv1::__cxa_free_exception): Use __cxa_refcounted_exception
instead of __cxa_exception.
* libsupc++/eh_throw.cc (__gxx_exception_cleanup,
__cxxabiv1::__cxa_throw): Likewise.
* libsupc++/eh_ptr.cc (std::rethrow_exception,
std::__exception_ptr::exception_ptr::_M_addref,
std::__exception_ptr::exception_ptr::_M_release,
__gxx_dependent_exception_cleanup): Likewise.
* testsuite/18_support/exception/38732.cc: New test.
--- libstdc++-v3/libsupc++/unwind-cxx.h.jj 2008-10-23 13:21:44.000000000 +0200
+++ libstdc++-v3/libsupc++/unwind-cxx.h 2009-01-07 12:57:55.000000000 +0100
@@ -1,5 +1,5 @@
// -*- C++ -*- Exception handling and frame unwind runtime interface routines.
-// Copyright (C) 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008
+// Copyright (C) 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009
// Free Software Foundation, Inc.
//
// This file is part of GCC.
@@ -53,9 +53,6 @@ namespace __cxxabiv1
struct __cxa_exception
{
- // Manage this header.
- _Atomic_word referenceCount;
-
// Manage the exception object itself.
std::type_info *exceptionType;
void (*exceptionDestructor)(void *);
@@ -92,6 +89,14 @@ struct __cxa_exception
_Unwind_Exception unwindHeader;
};
+struct __cxa_refcounted_exception
+{
+ // Manage this header.
+ _Atomic_word referenceCount;
+ // __cxa_exception must be last, and no padding can be after it.
+ __cxa_exception exc;
+};
+
// A dependent C++ exception object consists of a wrapper around an unwind
// object header with additional C++ specific information, containing a pointer
// to a primary exception object.
@@ -227,6 +232,21 @@ __get_exception_header_from_ue (_Unwind_
return reinterpret_cast<__cxa_exception *>(exc + 1) - 1;
}
+// Acquire the C++ refcounted exception header from the C++ object.
+static inline __cxa_refcounted_exception *
+__get_refcounted_exception_header_from_obj (void *ptr)
+{
+ return reinterpret_cast<__cxa_refcounted_exception *>(ptr) - 1;
+}
+
+// Acquire the C++ refcounted exception header from the generic exception
+// header.
+static inline __cxa_refcounted_exception *
+__get_refcounted_exception_header_from_ue (_Unwind_Exception *exc)
+{
+ return reinterpret_cast<__cxa_refcounted_exception *>(exc + 1) - 1;
+}
+
static inline __cxa_dependent_exception *
__get_dependent_exception_from_ue (_Unwind_Exception *exc)
{
--- libstdc++-v3/libsupc++/eh_alloc.cc.jj 2008-10-23 13:21:44.000000000 +0200
+++ libstdc++-v3/libsupc++/eh_alloc.cc 2009-01-07 13:37:34.000000000 +0100
@@ -1,5 +1,5 @@
// -*- C++ -*- Allocate exception objects.
-// Copyright (C) 2001, 2002, 2003, 2004, 2005, 2006, 2008
+// Copyright (C) 2001, 2002, 2003, 2004, 2005, 2006, 2008, 2009
// Free Software Foundation, Inc.
//
// This file is part of GCC.
@@ -103,7 +103,7 @@ __cxxabiv1::__cxa_allocate_exception(std
{
void *ret;
- thrown_size += sizeof (__cxa_exception);
+ thrown_size += sizeof (__cxa_refcounted_exception);
ret = malloc (thrown_size);
if (! ret)
@@ -137,9 +137,9 @@ __cxxabiv1::__cxa_allocate_exception(std
__cxa_eh_globals *globals = __cxa_get_globals ();
globals->uncaughtExceptions += 1;
- memset (ret, 0, sizeof (__cxa_exception));
+ memset (ret, 0, sizeof (__cxa_refcounted_exception));
- return (void *)((char *)ret + sizeof (__cxa_exception));
+ return (void *)((char *)ret + sizeof (__cxa_refcounted_exception));
}
@@ -158,7 +158,7 @@ __cxxabiv1::__cxa_free_exception(void *v
emergency_used &= ~((bitmask_type)1 << which);
}
else
- free (ptr - sizeof (__cxa_exception));
+ free (ptr - sizeof (__cxa_refcounted_exception));
}
--- libstdc++-v3/libsupc++/eh_throw.cc.jj 2008-10-23 13:21:44.000000000 +0200
+++ libstdc++-v3/libsupc++/eh_throw.cc 2009-01-07 13:43:11.000000000 +0100
@@ -1,5 +1,5 @@
// -*- C++ -*- Exception handling routines for throwing.
-// Copyright (C) 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008
+// Copyright (C) 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009
// Free Software Foundation, Inc.
//
// This file is part of GCC.
@@ -38,21 +38,22 @@ static void
__gxx_exception_cleanup (_Unwind_Reason_Code code, _Unwind_Exception *exc)
{
// This cleanup is set only for primaries.
- __cxa_exception *header = __get_exception_header_from_ue (exc);
+ __cxa_refcounted_exception *header
+ = __get_refcounted_exception_header_from_ue (exc);
// We only want to be called through _Unwind_DeleteException.
// _Unwind_DeleteException in the HP-UX IA64 libunwind library
// returns _URC_NO_REASON and not _URC_FOREIGN_EXCEPTION_CAUGHT
// like the GCC _Unwind_DeleteException function does.
if (code != _URC_FOREIGN_EXCEPTION_CAUGHT && code != _URC_NO_REASON)
- __terminate (header->terminateHandler);
+ __terminate (header->exc.terminateHandler);
#ifdef _GLIBCXX_ATOMIC_BUILTINS_4
if (__sync_sub_and_fetch (&header->referenceCount, 1) == 0)
{
#endif
- if (header->exceptionDestructor)
- header->exceptionDestructor (header + 1);
+ if (header->exc.exceptionDestructor)
+ header->exc.exceptionDestructor (header + 1);
__cxa_free_exception (header + 1);
#ifdef _GLIBCXX_ATOMIC_BUILTINS_4
@@ -66,23 +67,24 @@ __cxxabiv1::__cxa_throw (void *obj, std:
void (*dest) (void *))
{
// Definitely a primary.
- __cxa_exception *header = __get_exception_header_from_obj (obj);
+ __cxa_refcounted_exception *header
+ = __get_refcounted_exception_header_from_obj (obj);
header->referenceCount = 1;
- header->exceptionType = tinfo;
- header->exceptionDestructor = dest;
- header->unexpectedHandler = __unexpected_handler;
- header->terminateHandler = __terminate_handler;
- __GXX_INIT_PRIMARY_EXCEPTION_CLASS(header->unwindHeader.exception_class);
- header->unwindHeader.exception_cleanup = __gxx_exception_cleanup;
+ header->exc.exceptionType = tinfo;
+ header->exc.exceptionDestructor = dest;
+ header->exc.unexpectedHandler = __unexpected_handler;
+ header->exc.terminateHandler = __terminate_handler;
+ __GXX_INIT_PRIMARY_EXCEPTION_CLASS(header->exc.unwindHeader.exception_class);
+ header->exc.unwindHeader.exception_cleanup = __gxx_exception_cleanup;
#ifdef _GLIBCXX_SJLJ_EXCEPTIONS
- _Unwind_SjLj_RaiseException (&header->unwindHeader);
+ _Unwind_SjLj_RaiseException (&header->exc.unwindHeader);
#else
- _Unwind_RaiseException (&header->unwindHeader);
+ _Unwind_RaiseException (&header->exc.unwindHeader);
#endif
// Some sort of unwinding error. Note that terminate is a handler.
- __cxa_begin_catch (&header->unwindHeader);
+ __cxa_begin_catch (&header->exc.unwindHeader);
std::terminate ();
}
--- libstdc++-v3/libsupc++/eh_ptr.cc.jj 2008-10-23 13:21:44.000000000 +0200
+++ libstdc++-v3/libsupc++/eh_ptr.cc 2009-01-07 13:40:44.000000000 +0100
@@ -1,5 +1,5 @@
// -*- C++ -*- Implement the members of exception_ptr.
-// Copyright (C) 2008 Free Software Foundation, Inc.
+// Copyright (C) 2008, 2009 Free Software Foundation, Inc.
//
// This file is part of GCC.
//
@@ -84,8 +84,8 @@ std::__exception_ptr::exception_ptr::_M_
{
if (_M_exception_object)
{
- __cxa_exception *eh =
- __get_exception_header_from_obj (_M_exception_object);
+ __cxa_refcounted_exception *eh =
+ __get_refcounted_exception_header_from_obj (_M_exception_object);
__sync_add_and_fetch (&eh->referenceCount, 1);
}
}
@@ -96,12 +96,12 @@ std::__exception_ptr::exception_ptr::_M_
{
if (_M_exception_object)
{
- __cxa_exception *eh =
- __get_exception_header_from_obj (_M_exception_object);
+ __cxa_refcounted_exception *eh =
+ __get_refcounted_exception_header_from_obj (_M_exception_object);
if (__sync_sub_and_fetch (&eh->referenceCount, 1) == 0)
{
- if (eh->exceptionDestructor)
- eh->exceptionDestructor (_M_exception_object);
+ if (eh->exc.exceptionDestructor)
+ eh->exc.exceptionDestructor (_M_exception_object);
__cxa_free_exception (_M_exception_object);
_M_exception_object = 0;
@@ -191,22 +191,22 @@ __gxx_dependent_exception_cleanup (_Unwi
{
// This cleanup is set only for dependents.
__cxa_dependent_exception *dep = __get_dependent_exception_from_ue (exc);
- __cxa_exception *header =
- __get_exception_header_from_obj (dep->primaryException);
+ __cxa_refcounted_exception *header =
+ __get_refcounted_exception_header_from_obj (dep->primaryException);
// We only want to be called through _Unwind_DeleteException.
// _Unwind_DeleteException in the HP-UX IA64 libunwind library
// returns _URC_NO_REASON and not _URC_FOREIGN_EXCEPTION_CAUGHT
// like the GCC _Unwind_DeleteException function does.
if (code != _URC_FOREIGN_EXCEPTION_CAUGHT && code != _URC_NO_REASON)
- __terminate (header->terminateHandler);
+ __terminate (header->exc.terminateHandler);
__cxa_free_dependent_exception (dep);
if (__sync_sub_and_fetch (&header->referenceCount, 1) == 0)
{
- if (header->exceptionDestructor)
- header->exceptionDestructor (header + 1);
+ if (header->exc.exceptionDestructor)
+ header->exc.exceptionDestructor (header + 1);
__cxa_free_exception (header + 1);
}
@@ -217,7 +217,8 @@ void
std::rethrow_exception(std::exception_ptr ep)
{
void *obj = ep._M_get();
- __cxa_exception *eh = __get_exception_header_from_obj (obj);
+ __cxa_refcounted_exception *eh
+ = __get_refcounted_exception_header_from_obj (obj);
__cxa_dependent_exception *dep = __cxa_allocate_dependent_exception ();
dep->primaryException = obj;
--- libstdc++-v3/testsuite/18_support/exception/38732.cc.jj 2009-01-07 14:35:57.000000000 +0100
+++ libstdc++-v3/testsuite/18_support/exception/38732.cc 2009-01-07 14:34:24.000000000 +0100
@@ -0,0 +1,93 @@
+// Copyright (C) 2009 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library. This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 2, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING. If not, write to the Free
+// Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
+// USA.
+
+#include <typeinfo>
+#include <exception>
+#include <cstddef>
+#include "unwind.h"
+#include <testsuite_hooks.h>
+
+// Before exception_ptr was introduced, some programs copied
+// part of unwind-cxx.h and used __cxa_get_globals to get at the
+// current exceptionType. __cxa_exception structure is described in the
+// C++ ABI, so they have the right to assume it works.
+// Ensure it is true.
+
+struct __cxa_exception
+{
+ std::type_info *exceptionType;
+ void (*exceptionDestructor)(void *);
+ std::unexpected_handler unexpectedHandler;
+ std::terminate_handler terminateHandler;
+ __cxa_exception *nextException;
+ int handlerCount;
+#ifdef __ARM_EABI_UNWINDER__
+ __cxa_exception* nextPropagatingException;
+ int propagationCount;
+#else
+ int handlerSwitchValue;
+ const unsigned char *actionRecord;
+ const unsigned char *languageSpecificData;
+ _Unwind_Ptr catchTemp;
+ void *adjustedPtr;
+#endif
+ _Unwind_Exception unwindHeader;
+};
+
+struct __cxa_eh_globals
+{
+ __cxa_exception *caughtExceptions;
+ unsigned int uncaughtExceptions;
+#ifdef __ARM_EABI_UNWINDER__
+ __cxa_exception* propagatingExceptions;
+#endif
+};
+
+extern "C" __cxa_eh_globals *__cxa_get_globals () throw();
+
+// PR libstdc++/38732
+void test01 ()
+{
+ bool test __attribute__((unused)) = true;
+ try {
+ throw 0;
+ } catch(...) {
+ __cxa_exception *exc = __cxa_get_globals()->caughtExceptions;
+ VERIFY ( exc != NULL );
+ VERIFY ( typeid(int) == *exc->exceptionType );
+ }
+ try {
+ throw 0LL;
+ } catch(...) {
+ __cxa_exception *exc = __cxa_get_globals()->caughtExceptions;
+ VERIFY ( exc != NULL );
+ VERIFY ( typeid(long long int) == *exc->exceptionType );
+ }
+ try {
+ throw 0.0;
+ } catch(...) {
+ __cxa_exception *exc = __cxa_get_globals()->caughtExceptions;
+ VERIFY ( exc != NULL );
+ VERIFY ( typeid(double) == *exc->exceptionType );
+ }
+}
+
+int main ()
+{
+ test01 ();
+}
Jakub
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