Yet another XLC bug: wrong handling of array new operator with default arguments

[Steve Poole]

Oh dear - ok, I'll pass it along.   I assume you've got a work around for this at the moment?


On 6 Jun 2013, at 17:47, Volker Simonis <volker.simonis at gmail.com> wrote:

> Hi Steve,
> 
> during the merge with the latest HotSpot version Goetz found yet another bug in XLC.
> 
> I managed to break it down into the following minimal C++ program ('array_new.cpp' - see attachment).
> 
> In the example, the size of a Foo<Buffer> obejct should be 42 bytes and consequently the size of an array of 10 Foo<Buffer> obejcts should always be 420 bytes. However in the first allocation of the example program, the array new allocator of Foo gets called with a size argument of 10 (which is the arity of the array to allocate) instead of its size (which would be 420). This is wrong, because it allocates to few storage for the array. This leads to crashes if the array will be accessed later on.
> 
> $ xlc++ array_new.cpp
> $ ./a.out
> sizeof(Foo<Buffer>[10]) = 420
> Foo::new [](size=10, foo=0)
> Foo::new [](size=420, foo=123)
> sizeof(Foo<Buf>[10]) = 420
> Foo::new [](size=420, foo=0)
> Foo::new [](size=420, foo=123)
> 
> Notice that all the other allocations are successful because they either explicitly specify the default argument of the array new operator or because  they use POD data type (struct 'Buf' which has no constructor instead of struct 'Buffer') as template argument for Foo.
> 
> The error occurs with both XLC 12:
> 
> IBM XL C/C++ for AIX, V12.1 (5765-J02, 5725-C72)
> Version: 12.01.0000.0003
> 
> and XLC 10:
> 
> IBM XL C/C++ for AIX, V10.1
> Version: 10.01.0000.0015
> 
> Could you please open a bug report for this issue and urge your XLC colleagues to fix this issue as fast as possible because this is a show-stopper for our current plan to merge our PPC/AIX HotSpot port into the the master repository.
> 
> Thank you and best regards,
> Volker
> 
> PS: in HotSpot this issue appears in http://hg.openjdk.java.net/hsx/hotspot-main/hotspot/file/tip/src/share/vm/utilities/events.hpp where the event loggers are initialized:
> 
>        88   EventLogBase<T>(const char* name, int length = LogEventsBufferEntries):
>        89     _name(name),
>        90     _length(length),
>        91     _count(0),
>        92     _index(0),
>        93     _mutex(Mutex::event, name) {
>        94     _records = new EventRecord<T>[length];
>        95   }
> 
> because 'EventLogBase' is derived from 'CHeapObj' which has an array new operator with an additional default argument. It finally leads to crashes in various places where the loggers are used during runtime.
> 
> <array_new.cpp>

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