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OpenCL<sup>TM</sup> API Headers

This repository contains C language headers for the OpenCL API.

The authoritative public repository for these headers is located at:

https://github.com/KhronosGroup/OpenCL-Headers

Issues, proposed fixes for issues, and other suggested changes should be created using Github.

Build instructions

While the OpenCL Headers can be built and installed in isolation, it is part of the OpenCL SDK. If looking for streamlined build experience and a complete development package, refer to the SDK build instructions instead of the following guide.

Dependencies

The OpenCL Headers CMake package support uses CMake for its build system. If CMake is not provided by your build system or OS package manager, please consult the CMake website.

Example Build

While the headers may just be copied as-is, this repository also contains a CMake script with an install rule to allow for packaging the headers.

cmake -S . -B build -DCMAKE_INSTALL_PREFIX=/chosen/install/prefix
cmake --build build --target install

Example Use

Example CMake invocation

cmake -D CMAKE_PREFIX_PATH=/chosen/install/prefix /path/to/opencl/app

and sample CMakeLists.txt

cmake_minimum_required(VERSION 3.0)
cmake_policy(VERSION 3.0...3.18.4)
project(proj)
add_executable(app main.cpp)
find_package(OpenCLHeaders REQUIRED)
target_link_libraries(app PRIVATE OpenCL::Headers)

Branch Structure

The OpenCL API headers in this repository are Unified headers and are designed to work with all released OpenCL versions. This differs from previous OpenCL API headers, where version-specific API headers either existed in separate branches, or in separate folders in a branch.

Compiling for a Specific OpenCL Version

By default, the OpenCL API headers in this repository are for the latest OpenCL version (currently OpenCL 3.0). To use these API headers to target a different OpenCL version, an application may #define the preprocessor value CL_TARGET_OPENCL_VERSION before including the OpenCL API headers. The CL_TARGET_OPENCL_VERSION is a three digit decimal value representing the OpenCL API version.

For example, to enforce usage of no more than the OpenCL 1.2 APIs, you may include the OpenCL API headers as follows:

#define CL_TARGET_OPENCL_VERSION 120
#include <CL/opencl.h>

Controlling Function Prototypes

By default, the OpenCL API headers in this repository declare function prototypes for every known core OpenCL API and OpenCL extension API. If this is not desired, the declared function prototypes can be controlled by the following preprocessor defines:

CL_NO_PROTOTYPES: No function prototypes will be declared. This control applies to core OpenCL APIs and OpenCL extension APIs.
CL_NO_CORE_PROTOTYPES: No function prototypes will be declared for core OpenCL APIs.
CL_NO_EXTENSION_PROTOTYPES: No function prototypes will be declared for OpenCL extension APIs. This control applies to all OpenCL extension APIs.
CL_NO_ICD_DISPATCH_EXTENSION_PROTOTYPES: No function prototypes will be declared for OpenCL extension APIs that are in the ICD dispatch table for historical reasons.
CL_NO_NON_ICD_DISPATCH_EXTENSION_PROTOTYPES: No function prototypes will be declared for OpenCL extension APIs that are not in the ICD dispatch table.

For example, to declare function prototypes for core OpenCL 3.0 APIs only, you may include the OpenCL API headers as follows:

#define CL_TARGET_OPENCL_VERSION 300
#define CL_NO_EXTENSION_PROTOTYPES
#include <CL/opencl.h>

Compatibility Notes

OpenCL values backward compatibility and in most cases an application using an older version of the OpenCL API headers can seamlessly update to a newer version of the OpenCL API headers. In rare cases, though, the OpenCL API headers may break backward compatibility:

Very rarely, there may be bugs or other issues in the OpenCL API headers that cannot be fixed without breaking compatibility.
The OpenCL API headers for provisional features or provisional extensions may be changed in a way that breaks compatibility.

Applications or libraries that require stable OpenCL API headers are encouraged to use tagged or released OpenCL API headers. We will do our best to document any breaking changes in the description of each release. The OpenCL API headers are tagged at least as often as each OpenCL specification release.

Directory Structure

README.md               This file
LICENSE                 Source license for the OpenCL API headers
CL/                     Unified OpenCL API headers tree

Packaging

For packaging instructions, see RELEASE.md in the OpenCL SDK repository.

License

See LICENSE.

OpenCL and the OpenCL logo are trademarks of Apple Inc. used by permission by Khronos.