SPrinter: A Static Checker for Finding Smart Pointer Errors in C++ Programs

Xutong Ma, Jiwei Yan, Yaqi Li, Jun Yan and Jian Zhang

Institute of Software, Chinese Academy of Sciences

maxt@ios.ac.cn

Manual and Automated Memory Management

• Manual Management
• Allocations and deallocations are verbose
• Memory errors: Memory Leak, Use after Free, Double Free, etc.
• Automated Management (through Smart Pointers)
• Automated (implicit) deallocations
• Can be used like stack memory
• Smart Pointer Errors (not absolutely safe)
• Reason of Smart Pointer Errors
• Basic concepts are unfriendly to beginners
• APIs of smart pointer classes are confusing
• Programmers are credulous when using smart pointers

Manual Memory Management

Automated Memory Management (Smart Pointer)

RAII and Smart Pointer

• Smart Pointer:

• Resource Acquisition Is Initialization (RAII)
• Bind the life cycle of resources to container objects
• Deallocate the resource when:
• the container goes out of scope
• the memory is no longer referenced by any containers.

Resource

Container

Ownership and Smart Pointer API

• Ownership indicates the responsibility to deallocate the managed heap memory object.
• The Smart Pointer APIs are used to manage the ownership rather than allocate or deallocate the memory directly.

Error Patterns

• Unconscious ownership transfer

• Leaked ownership

• Forked ownership

• Invalid memory ownership

Error Patterns

• Unconscious ownership transfer

• Leaked ownership

• Forked ownership

• Invalid memory ownership

Unconscious ownership transfer

• Using auto pointers in STL containers.
• Declaring private auto pointer fields with default copy constructor and assignment operator.

Leaked ownership

• Unused return values of release method.
• Using release method as an observer.
• Deallocating the return value of the get method.

OR

Forked ownership

• Using raw pointers to initialize smart pointers.
• Multiple initializations with the same raw pointer.

Double Free

Freed

Invalid memory ownership

• Using non-heap memory to initialize a smart pointer.
• Array and non-array type mismatch.
• Using weak pointers without checking for validity.

Implementation

• Based on Clang-Tidy Framework
• Using AST Matchers to detect bad usages of Smart Pointer APIs

Usage

• Direct execute on command line:
• clang-tidy -checks='-*,smartpointersafety-*' source.cpp
• source.cpp:3:23: warning: Initiating smart pointer with raw pointer.
• shared_ptr<int> sp1(p);
• ^
• 1 warning generated.
• Integrated into editors:
• Official tutorial for clang-tidy: https://clang.llvm.org/extra/clang-tidy/Integrations.html

Evaluation - Manual Benchmark Instances

Evaluation - Open Source Projects

Q & A

Thank you.