C Specification

#pragma OPENCL EXTENSION extension_name : behavior
#pragma OPENCL EXTENSION all : behavior



The #pragma OPENCL EXTENSION directive is a simple, low-level mechanism to set the behavior for each extension. It does not define policies such as which combinations are appropriate; those must be defined elsewhere. The order of directives matter in setting the behavior for each extension. Directives that occur later override those seen earlier. The all variant sets the behavior for all extensions, overriding all previously issued extension directives, but only if the behavior is set to disable.

The initial state of the compiler is as if the directive #pragma OPENCL EXTENSION all : disable was issued, telling the compiler that all error and warning reporting must be done according to this specification, ignoring any extensions.

Every extension which affects the OpenCL language semantics, syntax or adds built-in functions to the language must create a preprocessor #define that matches the extension name string. This #define would be available in the language if and only if the extension is supported on a given implementation.


This document describes the list of optional features supported by OpenCL 2.1. Optional extensions may be supported by some OpenCL devices. Optional extensions are not required to be supported by a conformant OpenCL implementation, but are expected to be widely available; they define functionality that is likely to move into the required feature set in a future revision of the OpenCL specification

OpenCL extensions approved by the OpenCL working group can be promoted to required core features in later revisions of OpenCL. When this occurs, the extension specifications are merged into the core specification. Functions and enumerants that are part of such promoted extensions will have the KHR affix removed. OpenCL implementations of such later revisions must also export the name strings of promoted extensions in the CL_PLATFORM_EXTENSIONS or CL_DEVICE_EXTENSIONS string, and support the KHR-affixed versions of functions and enumerants as a transition aid.


An extension which adds the extension string "cl_khr_3d_image_writes" should also add a preprocessor #define called cl_khr_3d_image_writes. A kernel can now use this preprocessor #define to do something like the following:

#ifdef cl_khr_3d_image_writes
    // do something using the extension
    // do something else or #error!

See Also

Document Notes

For more information, see the OpenCL Extension Specification at URL

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