2017 LLVM Developers’ Meeting: . Finkel “The Type Sanitizer: Free Yourself from ... ”

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The Type Sanitizer: Free Yourself from -fno-strict-aliasing - Hal Finkel

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LLVM provides a metadata-driven type-based alias analysis (TBAA), designed to represent pointer aliasing restrictions from C/C++ type-based aliasing rules, and used by many frontends, that can serve as an important optimization enabler. In the context of C/C++, the programmer bears most of the responsibility for ensuring that the program obeys these rules. As you might expect, programmers often get this wrong. In fact, many programs are compiled with -fno-strict-aliasing, the flag which disables the production of TBAA metadata. LLVM has long featured an extensive set of sanitizers: instrumentation-based tools that can detect violations of the rules restricting defined program behavior. These tools have relatively-low overhead and find an impressive number of bugs. In this talk, I'll describe the type sanitizer. This new sanitizer detects violations of type-aliasing rules allowing the programmer to pinpoint and correct problematic code. I'll cover how the type sanitizer leverages existing TBAA metadata to guide its instrumentation and how it was implemented with relative ease by taking advantage of common infrastructure within compiler-rt. Finally, I'll demonstrate some results from applying the type sanitizer to widely-used open-source software.
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