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Doop Developer Guide

This document1 describes the design, implementation, and usage of the Java-based Doop scaffolding.

Contents

Overview {#overview}

Doop is a framework for Java pointer analysis. It is implemented in Datalog, Java and Groovy providing:

  • A Java-based API for running points-to analyses for Java programs (Doop Core API).
  • A standalone application for running the analyses through a command-line interface (Doop CLI).

Doop uses Gradle as its build system.

Doop uses either [Logicblox] (http://www.logicblox.com/) or [Souffle] (http://www.souffle-lang.com) as its Datalog engine. The Doop port on the Logicblox engine is currently deprecated.

Building Doop {#building}

This section describes the process of building Doop and its various options.

Clone the Doop repository {#building.cloning}

Clone the Doop repo from bitbucket:

hg clone https://bitbucket.org/yanniss/doop

Directory Structure {#building.structure}

The directory structure of the repository follows the established conventions for Java projects. Specifically, the repository contains the following directories:

  • docs: various documentation files with more in-depth information and elaborate examples.
  • gradle: contains the Gradle wrapper (gradlew) files 2.
  • lib: the custom runtime dependencies (the jars which cannot be automatically downloaded by Gradle, such as soot).
  • logic: the logic files (the datalog Doop analysis framework).
  • src: the Java/Groovy source files.

The src directory is structured according to the Gradle conventions Java, Groovy and Application plugins, containing the following sub-directories3:

  • main/groovy: The Doop Groovy sources (Core API, CLI).
  • main/java: The Doop Java sources (soot fact generation).
  • main/resources: The default Log4j properties (and any other Java-based resource files).

The repo also contains:

  • the Gradle build scripts (build.gradle and settings.gradle),
  • the Gradle wrapper invocation scripts (gradlew and gradlew.bat),
  • the .hgignore file.
  • the README file and this documentation.

Doop creates the following directories under DOOP_HOME:

  • build: compile-time produced files (class files).
  • out: runtime produced files (processed logic, LogicBlox workspace, etc).
  • results: symlinks to the analyses files.
  • logs: log files of the analyses, which are automatically recycled every day.

Using Gradle to Execute the Build Tasks {#building.gradle}

After cloning the repo, we can execute the build task of choice by issuing the following:

$ ./gradlew [name-of-task]

To list the build tasks supported, we can issue:

$ ./gradlew tasks

The main tasks available are the following:

  • classes - Assembles the Java and Groovy classes.
  • jar - Assembles a jar archive containing the classes.
  • distTar - Bundles the project as a tar archive. The file is the distribution artifact of the Doop analysis framework, as it offers Doop as a self-contained, standalone Java application with libs and automatically-generated OS specific scripts. This task should be used for generating the Doop distro to publish to a web site.
  • distZip - As above, but generates a zip archive.
  • installApp - Installs Doop the build/install directory (identical to producing distTar or distZip and unpacking the contents to the build/install directory).
  • run - Runs the Doop CLI directly (without installing it).
  • clean - Deletes the build directory (generated by Gradle for storing the output of the build tasks).
  • javadoc - Generates Javadoc API documentation for the Java source code.
  • groovydoc - Generates Groovydoc API documentation for the Groovy source code.
  • createProperties - Creates the skeleton of a doop properties file.

The Gradle build script {#building.script}

The Gradle build script (build.gradle) contains the settings and code required to execute the build tasks. The script uses Gradle's Groovy-based DSL to:

  • apply the Groovy and Application plugins,
  • set the source and target compatibility for the generated class files (currently, it has to be 1.6),
  • define the name of the Main class (for the CLI),
  • setup the jar repositories,
  • define the project's compile-time and run-time dependencies,
  • define the custom createProperties task,
  • customize the files to be included in the application distribution,
  • configure environment variables and system settings for running the CLI directly.

Running Doop {#running}

This section describes the various command line options supported for running Doop.

Main options {#running.main}

To list all the available options run Doop without any parameters (or with the -h flag). The main command line options are described in the README file:

  • -a, --analysis: The name of the analysis.
  • -i, --input: The jar file(s) to analyse.
  • --platform: The platform and version to use. Doop checks for the JRE-specific or Android-specific files in the $DOOP_PLATFORMS_LIB directory, while an alternate location can be provided through the --doop-platform-libs option. For instance, java_7 specifies the Java platform and the JRE 1.7 will be used to resolve library calls, while android_26 specifies the Android platform and the Android library version 26 (Marshmallow) will be used to resolve calls to the Android library).
  • --main: The name of the Java main class.
  • -t, --timeout: The analysis execution timeout in minutes.
  • -id, --identifier: The human-friendly identifier of the analysis (if not specified, Doop will generate one automatically).
  • --regex: The Java package names to analyse.
  • -p, --properties: Load options from the given properties file.

Analyze the Dacapo Benchmarks suite {#dacapo}

Doop provides special handling of the DaCapo Benchmarks suite. You can check the README file for more information on how to acquire those benchmarks.

For example, in order to analyze a DaCapo 2006 benchmark we could issue the following:

$ ./doop -a context-insensitive -i benchmarks/dacapo-2006/antlr.jar --dacapo

Respectively, for a DaCapo Bach benchmark we could issue the following:

$ ./doop -a context-insensitive -i benchmarks/dacapo-bach/avrora/avrora.jar --dacapo-bach

Design and Implementation {#design}

Goals {#design.goals}

The primary goals of the Java/Groovy part of Doop are the following:

  1. Offer an embeddable and multi-tenant Java/Groovy API for running the analyses.
  2. Develop a unified code-base that is highly maintainable, flexible and extensible.

The classes of the Core API {#design.api}

The core API is contained in the org.clyze.doop.core Groovy package and contains the following classes.

AnalysisFactory

A Factory for creating analyses. The class provides the following public methods:

newAnalysis(String id, String name, Map<String, AnalysisOption> options, List<String> jars)

newAnalysis(String id, String name, Map<String, AnalysisOption> options, InputResolutionContext ctx)

which create a new Analysis object. The methods check and verify that all provided information (id and name of the analysis, jar files and options) is correct, throwing an exception in case of error. The checks performed are based on the doop run script and are implemented using private or protected methods.

This class is extended by CommandLineAnalysisFactory to support creating Analysis objects from the CLI.

Analysis

An object that holds both:

  1. the analysis options and inputs
  2. the code to execute the individual phases/steps of the analysis.

The class implements the Runnable interface to support running analyses in separate threads. To this end, the public method:

void run()

provides the entry point for starting the execution of an analysis.

The class also provides the following public methods:

  • printStats() - print the statistics of the analysis (a la doop run script).
  • linResult() - links the results of the analysis (a la doop run script).
  • query(String query, Closure closure) - executes the given bloxbatch query (using the -query flag), providing each line of output to the given closure.
  • toString() - returns a representation of the analysis as a String (used for debugging).

All the other methods of the class are either private or protected, as they are used to implement "internal details" of executing an analysis.

AnalysisOption

A class that models an analysis option. Each option contains the following attributes:

  • id: The identifier of the option (as used internally by the code, the preprocessors, etc.).
  • name: The name of the option (as presented to the end-user).
  • optName: The shorthand name of the option (for usage in cli).
  • description: The description of the option (which is also presented to the end-user).
  • value: The value of the option.
  • validValues: Optional set of valid values.
  • multipleValues: Boolean flag indicating that the option accepts multiple values.
  • argName - The description of the option's value which will be displayed to the end-user. All String options should define an argName.
  • argInputType: The InputType for options that have a file as argument.
  • cli: Boolean flag indicating whether the option should be included in the CLI.
  • isMandatory: Boolean flag indicating whether the options is mandatory or not.
  • forCacheID: Boolean flag indicating whether the option should affect the computation of the cache ID.
  • forPreprocessor: Boolean flag indicating whether the option is used by the preprocessor.
  • changesFacts: Boolean flag indicating whether the option may affect the generated facts.

The use of this class allows us to significantly simplify and reduce the code required to process and manage the analysis options in the various Doop usage scenarios.

Doop

The low-level initialization point of the Java/Groovy part of the framework.

This class provides the following public method:

void initDoop(String homePath, String outPath)

which sets the two main paths for each Doop deployment:

  • the doop home path, which determines the location of the logic files,
  • the doop output path, which determines the location of the out directory generated by the framework.

The class also holds a list of all the available Analysis options (in the ANALYSIS_OPTIONS final field).

Finally, the Doop class provides the following helper methods for initializing the analysis options:

  • createDefaultAnalysisOptions(): obtains a Map<String, AnalysisOption> using the default values defined in the ANALYSIS_OPTIONS list.
  • overrideDefaultOptionsWithCLI(cli, filter): overrides the default options with the values contained in the CLI.
  • overrideDefaultOptionsWithPropertiesAndCLI(properties, cli, filter): overrides the default options with the values contained in the properties and the CLI. An option in the CLI superseeds a property one.

The filter accepted by the last two methods is a closure that filters the options that should be set. For example, the following invocation:

Doop.overrideDefaultOptionsWithPropertiesAndCLI(properties, cli) { AnalysisOption option ->
    option.cli == true
}

overrides only the options that have their cli boolean flag set to true.

Helper

A class that holds various helper methods for logging, executing external processes, working with files, etc.

org.clyze.doop.core.ImportGenerator

The fact declarations import generator. Mimics the behavior of the writeImport bash script.

Analysis inputs - the org.clyze.doop.input package

The org.clyze.doop.input package contains a simple mechanism for dealing with the various analysis inputs and dependencies (local jar files, local directories, remote jar URLs and jars held in the Maven Central repository). The mechanism is based on the Input, InputResolver and InputResolutionContext interfaces. The first holds a mapping from a String value to a set of local files, the second offers a mechanism to construct this mapping in an InputResolutionContext which ultimately holds the whole set of mappings between inputs and files.

Adding a new analysis option

To add a new analysis option to the framework, we need to:

  • define the option in the ANALYSIS_OPTIONS list. For String options, it is currently necessary to define the argName of the option.
  • implement the validation/checks required for the new option (if any) in the AnalysisFactory,
  • update the implementation of Analysis to take into account the new option during the execution of the analysis phases.

The classes of the Doop CLI {#design.cli}

Main

The entry point of the Doop framework. The Main class collects the command-line options supplied by the user and starts the execution of the analysis.

CommandLineAnalysisFactory

The class extends AnalysisFactory to enable the creation of a Analysis object from the command line arguments and/or a properties file.

Footnotes

  1. This document is to be used with Pandoc, using an invocation like the following:

    pandoc -f markdown -t html -s -o outfile infile ↩

  2. Using the Gradle wrapper is the suggested way to run Gradle, allowing us to build, run or deploy the project without installing Gradle manually (the wrapper downloads Gradle for us). ↩

  3. Although we use Gradle's Application plugin, the logic files are placed in the logic top-level directory and not in the src/dist sub-directory (which is the standard Gradle convention for placing files to be distributed along with the application). This helps us support running the analyses without installing the Doop app. ↩