About:
I am a Senior Engineer at Uber's Programming Systems Group, where I work primarily on developing static analysis tools for Java applications. My current focus is on improving application reliability by preventing broad categories of bugs using fast type-system based tools that run on every local compilation, while minimizing developer annotation burden. My research interests more broadly include static and dynamic analysis, modeling of third-party code behavior, as well as automated test generation and UI exploration for mobile applications. Previous to Uber I got my Ph.D. in Computer Science from Stanford University under the direction of Prof. Alex Aiken.
Tools:
NullAway

A fast, practical, static nullness checker for Java


NullAway takes in code following an intuitive annotation discipline, where values that might be null at runtime, must be annotated with @Nullable. It performs type-based local analysis to ensure that any pointer that gets dereferenced in annotated code cannot be null, and thus prevent NullPointerExceptions (NPEs). In our measurements, the build-time overhead of running NullAway is usually less than 20% of javac, which allows us to use it to analize all of Uber Android Java code on every local compilation.


with Manu Sridharan, Subarno Banerjee, and others at Uber

RxThreadEffectChecker

A static analysis tool for preventing UI access off the main thread in stream-based (RxJava/RxAndroid) Android applications.


The RxThreadEffectChecker is built on the Checker Framework, and particularly it works in tandem with their guieffect checker. It extends these checkers with awaraness of the ReactiveX stream-based threading model. We have deployed RxThreadEffectChecker at Uber and are working on a faster iteration of this tool, using the same type system.


with Benno Stein, Manu Sridharan, and others at Uber

Research Publications:
Safe stream-based programming with refinement types

Benno Stein, Lazaro Clapp, Manu Sridharan, Bor-Yuh Evan Chang
33rd ACM/IEEE International Conference on Automated Software Engineering, (ASE), 2018.

Eventually Sound Points-To Analysis with Missing Code

Osbert Bastani, Lazaro Clapp, Saswat Anand, Rahul Sharma, Alex Aiken
In submission.

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Minimizing GUI Event Traces

Lazaro Clapp, Osbert Bastani, Saswat Anand, Alex Aiken
24th ACM SIGSOFT International Symposium on the Foundations of Software Engineering (FSE), 2016.

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Modelgen: Mining Explicit Information Flow Specifications from Concrete Executions

Lazaro Clapp, Saswat Anand, Alex Aiken
ACM International Symposium on Software Testing and Analysis (ISSTA), 2015.