Package org.graalvm.nativeimage.c.function

Annotation Interface CFunction

@Retention(RUNTIME) @Target(METHOD) public @interface CFunction
Denotes a native method that calls directly from Java to C, without following the JNI protocol. This means that there are no artificial additional parameters such as the JNI environment passed, and no marshaling or processing of arguments (such as creating handles for objects) is performed. If the method is non-static, the receiver will be ignored.

Parameter types and return types must not be Java reference types, only primitive Java types, word types and CEnum types are allowed. The representation of passed primitive values matches exactly how they are specified in the Java language, for example, int as a 32-bit signed integer or char as a 16-bit unsigned integer. boolean is specified as a single byte that corresponds to true if non-zero, and to false if zero. If a Word value is passed that points to a Java object, no guarantees are taken regarding its integrity as a pointer.

The class containing the annotated method must be annotated with CContext.

Note that this annotation must not be used for native functions that use variadic arguments (varargs) because varargs calling conventions are not supported and even a declaration with a specific non-varargs signature can be incompatible with vararg target functions on some platforms.

Since:
19.0

  • Nested Class Summary

    Nested Classes
    Modifier and Type
    Class
    Description
    static enum 
    CFunction.Transition
    Describes the thread state transition performed when the C function is invoked.

  • Optional Element Summary

    Optional Elements
    Modifier and Type
    Optional Element
    Description
    CFunction.Transition
    transition
    The Java-to-C thread transition code used when calling the function.
    String
    value
    The symbol name to use to link this method.

  • Element Details

    • value

      String value
      The symbol name to use to link this method. If no value is specified, the name of the method (without name mangling or a class name prefix) is used.
      Since:
      19.0
      Default:
      ""

    • transition

      CFunction.Transition transition
      The Java-to-C thread transition code used when calling the function.
      Since:
      19.0
      Default:
      TO_NATIVE