RFR(S): 8039805: Fix the signature of the global new/delete operators in allocation.cpp

Volker Simonis volker.simonis at gmail.com
Wed Apr 9 16:34:41 UTC 2014


could you please review and sponsor the following small change:


which fixes the signature of the global new/delete operators in allocation.cpp

For non-product builds allocation.cpp defines global new/delete
operators which shut down the VM if they get called at runtime. The
rational behind this is that the these global operators should never
be used in HotSpot.

Unfortunately, the signature of some of these operators doesn't
conform to the C++ standard which confuses some C++ compilers. For a
more detailed explanation of the C++ background of this issue see the
new comments in allcoation.cpp and the end of this mail.

This change also replaces the asserts in the operators with guarantees
because the code may also be active in not-product (aka. 'optimized')

Finally, the webrev fixes two places in the AIX-port which used the
global new operator. After the change we can now remove the definition
of ALLOW_OPERATOR_NEW_USAGE from aix/makefiles/vm.make.

I have also removed ALLOW_OPERATOR_NEW_USAGE from
bsd/makefiles/vm.make and the corresponding comments in allcoation.cpp
which state that on Mac OS X the global new/delete operators from the
HotSpot cause problems together with usages of these operators from
the class library such as the ones from
Java_sun_security_ec_ECKeyPairGenerator_generateECKeyPair. I couldn’t
observe any such problems but if anybody has some concrete concerns
I'm ready to remove this part from the webrev.

I've build and tested these changes on Linux/x86_64, Linux/ppc64,
Solaris/Sparc, Windows/x86_64, MacOS X and AIX/ppc64. I've especially
run the regression tests from sun/security/ec which exercise the
method Java_sun_security_ec_ECKeyPairGenerator_generateECKeyPair which
was mentioned to cause problems in conjunction with the globally
defined new/delete operators from the HotSpot but couldn't see any
issues, neither in the slowdebug nor in the optimized build.

Following some C++ background regarding the global new/delete operators:

In C++98/03 the throwing new operators are defined with the following signature:

void* operator new(std::size_tsize) throw(std::bad_alloc);
void* operator new[](std::size_tsize) throw(std::bad_alloc);

while all the other (non-throwing) new and delete operators are
defined with an empty throw clause (i.e. "operator delete(void* p)
throw()") which means that they do not throw any exceptions (see
section 18.4 of the C++ standard

In the new C++11/14 standard
the signature of the throwing new operators was changed by completely
omitting the throw clause (which effectively means they could throw
any exception) while all the other new/delete operators where changed
to have a 'nothrow' clause instead of an empty throw clause.

Unfortunately, the support for exception specifications among C++
compilers is still very fragile. While some more strict compilers like
AIX xlC or HP aCC reject to override the default throwing new operator
with a user operator with an empty throw() clause, the MS Visual C++
compiler warns for every non-empty throw clause like
throw(std::bad_alloc) that it will ignore the exception specification
(see http://msdn.microsoft.com/en-us/library/sa28fef8.aspx).

I've therefore changed the operator definitions such that they
correctly work with all currently supported compilers and in way which
should be upwards compatible with C++11/14.

Please notice that I'm aware of the discussion around "8021954: VM
SIGSEGV during classloading on MacOS; hs_err_pid file produced"
which introduced empty throw() clauses on all user defined new
operators. But I think the rational used for that change doesn't apply
here, because these global, user user defined new operators changed in
this webrev aren't meant to be really used. There only task is to
override the default, global operators (and therefore they need to
have the right signature) and to shut the VM down if they get called.

Thank you and best regards,

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