OutOfMemoryException being thrown on creation of an LS Serializer
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Key: XERCESC-1979
URL: https://issues.apache.org/jira/browse/XERCESC-1979
Project: Xerces-C++
Issue Type: Bug
Components: Miscellaneous
Affects Versions: 3.1.1
Environment: AIX 6.1 and AIX 7.1
32-bit binary distribution libraries of Xerces 3.1.1
Compiler (on AIX 6.1):
IBM XL C/C++ for AIX, V11.1 (5724-X13)
Version: 11.01.0000.0000
Driver Version: 11.01(C/C++) Level: 100304
C Front End Version: 11.00(C/C++) Level: 100301
C++ Front End Version: 11.01(C/C++) Level: 100304
High-Level Optimizer Version: 11.01(C/C++) and 13.01(Fortran) Level: 100301
Low-Level Optimizer Version: 11.01(C/C++) and 13.01(Fortran) Level: 100304
Reporter: Matt Dissinger
I am seeing with one of my companies' unit test binaries an
OutOfMemoryException being thrown when attempting to create an LS serializer.
The program code in question is:
{code}
xercesc::DOMImplementation* impl =
DOMImplementationRegistry::getDOMImplementation(XMLString::transcode("LS"));
impl->createLSSerializer();
{code}
We are currently only seeing this with one of our unit test binaries, and only
on AIX. We haven't seen this yet on our production binaries or on Solaris,
RedHat Enterprise Linux, or Windows. The root cause is an allocation of 0
bytes for which the ::operator new is returning a NULL pointer, and the
MemoryManagerImpl throws an OutOfMemoryException when this occurs. This
happens as a result of the DOMLSSerializerImpl object allocating a RefVectorOf
with an initial size of 0, and the base class BaseRefVectorOf's constructor
calling allocate with 0 bytes.
Even though the C++ standard does allow for allocations of 0 bytes, it is a
potential point of failure that can be avoided by not attempting the 0 byte
allocation. Since the standard does define that dereferencing a pointer
returned as a request for zero size is undefined, it should be safe to return
NULL for 0 byte allocations (3.7.4.1 - Allocation functions, point 2, from the
draft version here:
http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2010/n3035.pdf).
I've tested a change to the MemoryManagerImpl class which checks for 0 byte
allocations and immediately returns NULL rather than attempting an ::operator
new (0), and it has fixed the issue in our AIX environments.
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