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Instrumentation of Java libraries using OpenTelemetry.
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/*
 * Copyright The OpenTelemetry Authors
 * SPDX-License-Identifier: Apache-2.0
 */

package io.opentelemetry.javaagent.tooling.bytebuddy;

import io.opentelemetry.javaagent.bootstrap.ExceptionLogger;
import net.bytebuddy.ClassFileVersion;
import net.bytebuddy.asm.Advice.ExceptionHandler;
import net.bytebuddy.implementation.Implementation;
import net.bytebuddy.implementation.bytecode.StackManipulation;
import org.objectweb.asm.Label;
import org.objectweb.asm.MethodVisitor;
import org.objectweb.asm.Opcodes;

public final class ExceptionHandlers {
  // Bootstrap ExceptionLogger.class will always be resolvable, so we'll use it in the log name
  private static final String LOGGER_NAME = ExceptionLogger.class.getName().replace('.', '/');

  private static final ExceptionHandler EXCEPTION_STACK_HANDLER =
      new ExceptionHandler.Simple(
          new StackManipulation() {
            // Pops one Throwable off the stack. Maxes the stack to at least 2 (throwable, string).
            private final StackManipulation.Size size = new StackManipulation.Size(-1, 2);

            @Override
            public boolean isValid() {
              return true;
            }

            @Override
            public StackManipulation.Size apply(MethodVisitor mv, Implementation.Context context) {
              String name = context.getInstrumentedType().getName();

              // writes the following bytecode:
              // try {
              //   ExceptionLogger.logSuppressedError("exception in instrumentation", t);
              // } catch (Throwable t2) {
              // }
              Label logStart = new Label();
              Label logEnd = new Label();
              Label eatException = new Label();
              Label handlerExit = new Label();

              // Frames are only meaningful for class files in version 6 or later.
              boolean frames = context.getClassFileVersion().isAtLeast(ClassFileVersion.JAVA_V6);

              mv.visitTryCatchBlock(logStart, logEnd, eatException, "java/lang/Throwable");

              // stack: (top) throwable
              mv.visitLabel(logStart);
              mv.visitLdcInsn("Failed to handle exception in instrumentation for " + name);
              mv.visitInsn(Opcodes.SWAP); // stack: (top) throwable,string

              mv.visitMethodInsn(
                  Opcodes.INVOKESTATIC,
                  LOGGER_NAME,
                  "logSuppressedError",
                  "(Ljava/lang/String;Ljava/lang/Throwable;)V",
                  /* isInterface= */ false);
              mv.visitLabel(logEnd);
              mv.visitJumpInsn(Opcodes.GOTO, handlerExit);

              // if the runtime can't reach our ExceptionLogger,
              //   silently eat the exception
              mv.visitLabel(eatException);
              if (frames) {
                mv.visitFrame(Opcodes.F_SAME1, 0, null, 1, new Object[] {"java/lang/Throwable"});
              }
              mv.visitInsn(Opcodes.POP);
              // mv.visitMethodInsn(Opcodes.INVOKEVIRTUAL, "java/lang/Throwable",
              //    "printStackTrace", "()V", false);

              mv.visitLabel(handlerExit);
              if (frames) {
                mv.visitFrame(Opcodes.F_SAME, 0, null, 0, null);
                // there may be at most one frame at given code location, we need to add an extra
                // NOP instruction to ensure that there isn't a duplicate frame
                mv.visitInsn(Opcodes.NOP);
              }

              return size;
            }
          });

  public static ExceptionHandler defaultExceptionHandler() {
    return EXCEPTION_STACK_HANDLER;
  }

  private ExceptionHandlers() {}
}