jdk/test/langtools/tools/javac/flags/FlagsTest.java

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/**
 * @test
 * @bug 8211138 8215246 8362885
 * @summary Missing Flag enum constants
 * @library /tools/javac/lib
 * @modules jdk.compiler/com.sun.tools.javac.code
 * @compile FlagsTest.java
 * @run main/manual FlagsTest
 */
import com.sun.tools.javac.code.Flags;
import com.sun.tools.javac.code.Flags.FlagTarget;
import com.sun.tools.javac.code.Flags.NotFlag;
import com.sun.tools.javac.code.Flags.Use;
import java.lang.reflect.Field;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class FlagsTest {

    private static final int U2_SIZE = 16;

    public static void main(String[] args) throws Throwable {
        findFreeFlags();
    }

    private static void findFreeFlags() throws Throwable {
        Map<FlagTarget, Map<Long, List<Field>>> target2Flag2Fields = computeTarget2Flag2Fields();

        for (FlagTarget target : FlagTarget.values()) {
            long freeFlags = ~collectFlags(target2Flag2Fields, target);

            printFreeFlags(target.name(), freeFlags);
        }
    }

    private static Map<FlagTarget, Map<Long, List<Field>>> computeTarget2Flag2Fields() throws Throwable {
        Map<FlagTarget, Map<Long, List<Field>>> target2Flag2Fields = new HashMap<>();
        for (Field f : Flags.class.getFields()) {
            if (f.isAnnotationPresent(NotFlag.class)) {
                continue;
            }

            Use use = f.getAnnotation(Use.class);

            if (use == null) {
                throw new AssertionError("No @Use and no @NotFlag for: " + f.getName());
            }

            long flagValue = ((Number) f.get(null)).longValue();

            for (FlagTarget target : use.value()) {
                target2Flag2Fields.computeIfAbsent(target, _ -> new HashMap<>())
                        .computeIfAbsent(flagValue, _ -> new ArrayList<>())
                        .add(f);
            }
        }
        return target2Flag2Fields;
    }

    private static void printFreeFlags(String comment, long freeFlags) {
            System.err.print("free flags for " + comment + ": ");
            for (int bit = U2_SIZE; bit < Long.SIZE; bit++) { //lowest 16 bits are used in classfiles, never suggest adding anything there
                if ((freeFlags & (1L << bit)) != 0) {
                    System.err.print("1L<<" + bit + " ");
                }
            }
            System.err.println();
    }

    private static long collectFlags(Map<FlagTarget, Map<Long, List<Field>>> target2Flag2Fields, FlagTarget... forTargets) {
        long flags = 0;

        for (FlagTarget target : forTargets) {
            for (long used : target2Flag2Fields.get(target).keySet()) {
                flags |= used;
            }
        }

        return flags;
    }
}