H5T_OPEN is a macro that is mapped to either H5T_OPEN1 or H5T_OPEN2, depending on the needs of the application.
Such macros are provided to facilitate application compatibility. Their use and mappings are fully described in API Compatibility Macros in HDF5; we urge you to read that document closely.
When both the HDF5 library and the application are built and installed with no specific compatibility flags, H5T_OPENis mapped to the most recent version of the function, currently H5T_OPEN2. If the library and/or application is compiled for Release 1.6 emulation,H5T_OPEN will be mapped to H5T_OPEN1. Function-specific flags are available to override these settings on a function-by-function basis when the application is compiled.
Specific compile-time compatibility flags and the resulting mappings are as follows: