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API Changes

There are new API calls that require API Compatibility Macros in HDF5 1.14.0. There are, however, two API calls which have had their signature change.

H5Iregister_type() / H5I_free_t

The signature of H5Iregister_type() did not change, but the H5I_free_t callback it accepts did have its signature change to add an asynchronous request parameter. There is no API compatibility macro to paper over this change. The request parameter can be ignored in the callback if you are not concerned with asynchronous operations and future IDs. A description of how the request parameter should be used will be found in the (soon to be released) HDF5 Asynchronous Programming Guide.


typedef herr_t (*H5I_free_t)(void *obj);


typedef herr_t (*H5I_free_t)(void *obj, void **request);


The way optional operations are handled in the virtual object layer (VOL) changed significantly in HDF5 1.14.0. To better support this, the H5VLquery_optional() API call now takes an output flags parameter instead of a Boolean. Since the entire 1.12 VOL API has been deprecated, no API compatibility macro exists for this API call.


herr_t H5VLquery_optional(hid_t obj_id, H5VL_subclass_t subcls, int opt_type, hbool_t *supported);


herr_t H5VLquery_optional(hid_t obj_id, H5VL_subclass_t subcls, int opt_type, uint64_t *flags);

Virtual File Layer (VFL) Changes

The virtual file layer has changed in HDF5 1.14.0. Existing virtual file drivers (VFDs) will have to be updated to work with this version of the library..

For details, see the (soon to be released) 1.12 to 1.14. VFL Migration Guide.

Virtual Object Layer (VOL) Changes

The virtual object layer has changed significantly in HDF5 1.14.0 and the 1.12 VOL API is now considered deprecated and unsupported. Existing virtual object layer connectors shoul be updated to work with this version of the library.

For details, see the (soon to be released) 1.12 to 1.14. VOL Migration Guide.



Also see the video presentation: Moving Applications from 1.10 to 1.12

There were many existing functions that were modified in 1.12. Applications created with 1.10 or earlier that use these functions will encounter errors when compiled with 1.12. This page describes how to compile 1.10 and earlier applications with 1.12 without modifying an application, and provides details on the functions that changed for users who wish to update their applications:

For further information, see:

 Compiling 1.10 and earlier applications with 1.12

Applications that were created with earlier HDF5 releases may not compile with 1.12 by default. The API Compatibility Macros in HDF5 allow users to work around this issue. Users can specify a compatibility macro mapping for the version of HDF5 that an application was built with. For example, a 1.10 application can be built with 1.12 using either an application or library mapping as follows:

  • To compile an application built with a version of HDF5 that includes deprecated symbols (the default), make sure to pass -DH5_USE_110_API to the compiler. For example:


    Autotools:   h5cc -DH5_USE_110_API (C)

    CMake:       cmake -DCMAKE_C_FLAGS="-DH5_USE_110_API" (and likewise for other CMAKE_<LANG>_FLAGS)

  • To build an HDF5 library with the 1.10 APIs specify --with-default-api-version=v110 (Autotools) or -DDEFAULT_API_VERSION:STRING=v110 (CMake).


    ./configure --with-default-api-version=v110


    If using the source code packaged with CMake configuration files (CMake-hdf5-1.12.0*), edit HDF5options.cmake, and add this line:


    View the libhdf5.settings file to verify that the library was built with the 1.10 APIs:

    Default API mapping: v110 (under Features:)

However, users will not be able to take advantage of some of the new features in 1.12 if using these compatibility mappings.

Functions that changed

Functions were modified in HDF5 version 1.12 to support a token type used in the Virtual Object Layer (VOL) and to enable 64-bit selection encodings. These changes are described below.


The updated versions of the functions have a number (for eg '2' or '3') at the end of the original function name. The original versions of these functions were retained and renamed to have an earlier number (for eg '1') at the end of the original function name. A macro was created with the name of the original function. Please read API Compatibility Macros in HDF5 for more details on how the function names changed in version 1.12.

Token Type

In HDF5 1.12, a token type, H5O_token_t, replaced the address type, haddr_t, for representing locations in an HDF5 file. This change better supports the Virtual Object Layer (VOL), as the concept of an "address" does not make sense for many connectors. A token type is a more generic type that can function as both a connector and address location.

This change affected the following functions:

Original Function in 1.10 / Macro in 1.12 (H5xxx)

Deprecated Function in 1.12 (H5xxx1)

New Function (using token type)

(H5xxx2 or H5xxx3)




Encoding Properties

These functions were introduced in HDF5 version 1.12 as part of the H5Sencode format change to enable 64-bit selection encodings and a dataspace selection that is tied to a file. See the H5Sencode / H5Sdecode format change RFC for details.

Original Function in 1.10 / Macro in 1.12 (H5xxx)

Deprecated Function in 1.12 (H5xxx1)

New Function (H5xxx2)