kotlin-explorer

Introduction to the Kotlin Explorer

Kotlin Explorer is a powerful desktop tool designed to help developers understand the intricacies of Kotlin code by disassembling it into various formats. This tool transforms Kotlin code into Java bytecode, Android DEX bytecode, and Android OAT assembly, providing developers with a comprehensive understanding of how their Kotlin code is converted for execution on different platforms.

Key Features

1. Disassembling Kotlin Code:

   • Java Bytecode: Kotlin code can be converted to Java bytecode, allowing developers to see how Kotlin is translated to the Java Virtual Machine's language.
   • Android DEX Bytecode: The tool can also transform code into DEX format, which is essential for Android applications.
   • Android OAT Assembly: Offers insight into how code is prepared for execution using ahead-of-time compilation on Android devices.

2. Interactive Interface:

   • Users can type their Kotlin code into the left pane and view the disassembled code in the middle and right panes.
   • By default, the middle pane shows DEX bytecode, while the right displays the OAT assembly output.
   • Visibility of the panels can be adjusted through the View menu.

3. Optimization with R8:

   • Developers can enable R8 optimizations to improve the efficiency of their compiled code. However, enabling this affects the visibility of source line numbers in the output.

4. Convenient Tools:

   • Sync Lines: Synchronizes lines across source code, bytecode, and DEX views, providing a cohesive understanding of the code transformation. This feature may require R8 optimizations to be turned off.
   • Presentation Mode: Enlarges text for better visibility during presentations.
   • Automatic Build: The tool can be configured to compile code automatically upon startup.
   • Code Execution: Developers can compile and run their code locally, with any output directed to a logs panel.

5. Enhanced Analysis:

   • Clicking on jump instructions helps visually track control flow with indicative arrows.
   • Displays instruction and branch counts per method, aiding in efficient code analysis.
   • Highlighting capabilities to quickly identify all instances of a disassembled instruction or register.

6. Documentation and Logs:

   • Provides inline aarch64 (ARM 64 bit) architecture documentation for better understanding.
   • Access to logs and documentation is available through a simple menu toggle.

Using Kotlin Explorer with R8

R8 is a tool designed to optimize and shrink Java bytecode, and Kotlin Explorer incorporates features to leverage this tool's capabilities. By default, public classes and methods are preserved during optimization to facilitate detailed disassembly analysis. For a more realistic scenario, developers can disable this feature and use the @Keep annotation to specify which code sections should be preserved during optimization.

Setting Up Kotlin Explorer

Running Kotlin Explorer is straightforward with the command ./gradlew jvmRun. However, it requires certain environmental configurations:

• Android SDK & Kotlin Compiler: You must specify paths to the Android SDK and Kotlin compiler if they aren't set in $ANDROID_HOME and $KOTLIN_HOME, respectively.
• System Requirements: The tool needs java and javap to be in the system PATH.
• Android Device/Emulator: To display DEX bytecode and OAT assembly, a connected and compatible Android device or emulator is required with adb access.

Conclusion

Kotlin Explorer provides an excellent platform for developers to dissect and comprehend the inner workings of Kotlin code as it transitions through different stages of compilation and optimization. Its blend of intuitive features and rich analysis tools makes it an indispensable asset for Kotlin developers aiming to optimize and fully understand their codebases.