Programs with base classes from the C++ Standard Library compiled using -qobjmodel=ibm produces "1540-2200" error

Compiling the following example with the -qobjmodel=ibm option on AIX and z/OS will result in an error message indicating that the base classes have different object models.

#include <functional>

struct dummy_range_checker{};

struct trivial_converter_impl:

public std::unary_function<int, bool>,

public dummy_range_checker

{}; 

Use the following command to compile the example:

xlC t.cpp -qobjmodel=ibm -c

The following error message is generated by the compiler:

"t.cpp", line 5.8: 1540-2200 (S) Class "trivial_converter_impl" has base classes with different object models.

There is a limitation of using -qobjmodel=ibm with base classes from the C++ Standard Library.

All classes in the same inheritance hierarchy must have the same object model.

There are two object models available in the XL C++ compiler on AIX and z/OS:

• IBM object model, which can be specified by the -qobjmodel=ibm option or the #pragma object_model(ibm) pragma
• The classic object model, which can be specified by the -qobjmodel=classic option or the #pragma object_model(classic) pragma

The "1540-2200" error arises because:

• The std::unary_function base class has the classic object model since the C++ Standard Library from the XL C/C++ compiler headers on AIX and z/OS specifies #pragma object_model(classic) in the source code header.
• The dummy_range_checker base class has the ibm object model since the -qobjmodel=ibm option was used on the command line.

Thus the trivial_converter_impl derived class has conflicting object models.

The -qobjmodel=ibm option cannot be used to compile program source with base classes from the C++ Standard Library on AIX and z/OS.

You can use -qobjmodel=classic which is the default.