Preventive Service Planning
IBM XL C/C++ for AIX V12.1 is compatible with earlier versions of the XL C/C++ compiler; therefore, objects and libraries built with versions before V12.1 can be included in applications compiled with V12.1, with only one exception.
Objects and libraries built with versions before IBM XL C/C++ for AIX V12.1 can be included in applications compiled with V12.1.
The only exception is that if any objects or libraries use the OpenMP threadprivate variables and are compiled with XL C/C++ for AIX V10.1 or earlier, then any applications that use the same threadprivate variables in those objects or libraries and are compiled with V11.1 or later must be compiled with the -qsmp=noostls option.
Objects and libraries built with V11.1 or later do not have this issue.
The Backward compatibility issues section in the product documentation provides details about this issue.