org.graalvm.nativeimage.c.function.CEntryPoint Maven / Gradle / Ivy
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package org.graalvm.nativeimage.c.function;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
import java.util.function.BooleanSupplier;
import org.graalvm.nativeimage.CurrentIsolate;
import org.graalvm.nativeimage.Isolate;
import org.graalvm.nativeimage.IsolateThread;
import org.graalvm.nativeimage.LogHandler;
import org.graalvm.nativeimage.c.constant.CEnum;
import org.graalvm.nativeimage.c.constant.CEnumLookup;
import org.graalvm.nativeimage.c.constant.CEnumValue;
import org.graalvm.word.WordBase;
import org.graalvm.word.WordFactory;
/**
* Annotates a method that is a VM entry point. Such a method must be declared static, and is
* made accessible so that it can be called as a C function using the native ABI.
*
* An execution context must be passed as a parameter and can be either an {@link IsolateThread}
* that is specific to the current thread, or an {@link Isolate} for an isolate in which the current
* thread is attached. These pointers can be obtained via the methods of {@link CurrentIsolate}.
* When there is more than one parameter of these types, exactly one of the parameters must be
* annotated with {@link IsolateThreadContext} for {@link IsolateThread}, or {@link IsolateContext}
* for {@link Isolate}.
*
* Exceptions cannot be thrown to the caller and must be explicitly caught in the entry point
* method. Any uncaught exception causes the termination of the process after it is printed.
*
* No object types are permitted for parameters or return types; only primitive Java values,
* {@link WordBase word} values, and enum values are allowed. Enum values are automatically
* converted from integer constants to Java enum object constants. The enum class must have a
* {@link CEnum} annotation. When enum values are passed as parameters, the enum class must have a
* method with a {@link CEnumLookup} annotation. For enum return types, the enum class must have a
* method that is annotated with {@link CEnumValue}.
*
* @since 19.0
*/
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public @interface CEntryPoint {
/**
* The symbol name to use for this entry point.
*
* @since 19.0
*/
String name() default "";
/**
* Method documentation to be included in the header file, as an array of lines.
*
* @since 19.0
*/
String[] documentation() default "";
/**
* Provides an exception handler for all exceptions that are not handled explicitly by the entry
* point method. Java exceptions cannot be passed back to C code. If this property is not set,
* any uncaught exception is treated as a {@link LogHandler#fatalError() fatal error}.
*
* The provided class must have exactly one declared method (the exception handler method). The
* method must be static, have one parameter of type {@link Throwable} or {@link Object}, and
* must have a return type that is assignable to the return type of the annotated entry point
* method. That exception handler method is invoked when an exception reaches the entry point,
* and the exception is passed as the argument. The return value of the exception handler method
* is then the return value of the entry point, i.e., passed back to the C code.
*
* @since 19.0
*/
Class exceptionHandler() default FatalExceptionHandler.class;
/**
* Special placeholder value for {@link #exceptionHandler()} to print the caught exception and
* treat it as a {@link LogHandler#fatalError() fatal error}.
*
* @since 19.0
*/
final class FatalExceptionHandler implements ExceptionHandler {
private FatalExceptionHandler() {
}
}
/**
* Specifies that the annotated entry point method is an alias for a built-in function as
* provided by the C API. Such aliases may have extra arguments which are ignored and can be
* used to adhere to specific external conventions. The annotated method must be declared
* {@code native} and as such, cannot have its own code body. Refer to the C API for
* descriptions of the built-ins, and to the {@linkplain Builtin individual built-ins} for their
* requirements to the annotated method's signature.
*
* @since 19.0
*/
Builtin builtin() default Builtin.NO_BUILTIN;
/**
* If the supplier returns {@code true}, this entry point is added automatically when building a
* shared library. This means the method is a root method for compilation, and everything
* reachable from it is compiled too.
*
* The provided class must have a nullary constructor, which is used to instantiate the class.
* Then the supplier function is called on the newly instantiated instance.
*
* @since 22.0
*/
Class include() default AlwaysIncluded.class;
/**
* A {@link BooleanSupplier} that always returns {@code true}.
*
* @since 22.0
*/
final class AlwaysIncluded implements BooleanSupplier {
private AlwaysIncluded() {
}
/**
* Returns {@code true}.
*
* @since 22.0
*/
@Override
public boolean getAsBoolean() {
return true;
}
}
/**
* A {@link BooleanSupplier} that always returns {@code false}.
*
* @since 22.0
*/
final class NotIncludedAutomatically implements BooleanSupplier {
private NotIncludedAutomatically() {
}
/**
* Returns {@code false}.
*
* @since 22.0
*/
@Override
public boolean getAsBoolean() {
return false;
}
}
/**
* @since 22.0
*/
enum Publish {
/**
* Do not publish the entry point method.
*/
NotPublished,
/**
* Create a symbol for the entry point method in the native image.
*/
SymbolOnly,
/**
* Create a symbol for the entry point method in the native image, and if building a shared
* library image, also include a C declaration in the generated C header file.
*/
SymbolAndHeader,
}
/**
* Whether the entry point is part of the symbols and header files produced by Native Image.
*
* @since 22.0
*/
Publish publishAs() default Publish.SymbolAndHeader;
/**
* The built-in methods which can be {@linkplain #builtin() aliased}.
*
* @since 19.0
*/
enum Builtin {
/**
* The annotated method is not an alias for a built-in method.
*
* @since 19.0
*/
NO_BUILTIN,
/**
* The annotated method creates an isolate. An alias for this built-in requires no
* arguments, and must have a return type of {@link IsolateThread}. In case of an error,
* {@link WordFactory#nullPointer() NULL} is returned.
*
* @since 19.0
*/
CREATE_ISOLATE,
/**
* The annotated method attaches the current thread to an isolate. It requires a parameter
* of type {@link Isolate} with the isolate to attach to, and a return type of
* {@link IsolateThread}. In case of an error, {@link WordFactory#nullPointer() NULL} is
* returned.
*
* @since 19.0
*/
ATTACH_THREAD,
/**
* The annotated method returns the {@link IsolateThread} of the current thread in a
* specified {@link Isolate}. It requires a parameter of type {@link Isolate} for the
* isolate in question, and a return type of {@link IsolateThread}. In case of an error or
* if the current thread is not attached to the specified isolate,
* {@link WordFactory#nullPointer() NULL} is returned.
*
* @since 19.0
*/
GET_CURRENT_THREAD,
/**
* The annotated method returns the {@link Isolate} for an {@link IsolateThread}. It
* requires a parameter of type {@link IsolateThread}, and a return type of {@link Isolate}.
* In case of an error, {@link WordFactory#nullPointer() NULL} is returned.
*
* @since 19.0
*/
GET_ISOLATE,
/**
* The annotated method detaches the current thread, given as an {@link IsolateThread}, from
* an isolate. It requires a parameter of type {@link IsolateThread}, and a return type of
* {@code int} or {@code void}. With an {@code int} return type, zero is returned when
* successful, or non-zero in case of an error.
*
* @since 19.0
*/
DETACH_THREAD,
/**
* The annotated method tears down the specified isolate. It requires a parameter of type
* {@link IsolateThread}, and a return type of {@code int} or {@code void}. With an
* {@code int} return type, zero is returned when successful, or non-zero in case of an
* error.
*
* @since 19.0
*/
TEAR_DOWN_ISOLATE,
}
/**
* Designates an {@link IsolateThread} parameter to use as the execution context. At most one
* parameter can be annotated with this annotation or {@link IsolateContext}.
*
* @since 19.0
*/
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.PARAMETER)
@interface IsolateThreadContext {
}
/**
* Designates an {@link Isolate} parameter to use as the execution context. At most one
* parameter can be annotated with this annotation or {@link IsolateThreadContext}.
*
* @since 19.0
*/
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.PARAMETER)
@interface IsolateContext {
}
/**
* Marker interface for all {@link CEntryPoint#exceptionHandler() exception handler} classes.
*
* @since 22.0
*/
interface ExceptionHandler {
}
}