Unaligned accesses in C/C++: what, why and solutions to do it properly

CPUs used to perform better when memory accesses are aligned, that is when the pointer value is a multiple of the alignment value. This differentiation still exists in current CPUs, and still some have only instructions that perform aligned accesses. To take into account this issue, the C standard has alignment rules in place, and so the compilers exploit them to generate efficient code whenever possible. As we will see in this article, we need to be careful while casting pointers around to be sure not to break any of these rules. The goal of this article is to be educative by showcasing the problem and by giving some solutions to easily get over it.

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Back from CppCon 2018

Two engineers from QuarksLab had talks accepted at CppCon this year: two tools presentation, Easy::jit, and Frozen; and a general introduction to the ELF format. It's hard to cope with the 9 hours of jet-lag, but it is definitively worth the effort, so here is our conf report!

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Easy::jit: Just-In-Time compilation for C++

Easy::jit is a library that brings just-in-time compilation to C++ codes. It allows developers to jit-compile some functions and specializing (part of) their parameters. Just-in-time compilation is done on-demand and controlled by the developer. The project is available on github .

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LIEF 0.9

This blog post introduces major changes in LIEF 0.9 as well as work in progress features that will be integrated in further releases. Changelog is available here.

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Frozen - zero cost initialization for immutable containers and various algorithms

A new version of Frozen, an open source, header-only library that provides fast, immutable, constexpr-compatible implementation of std::search, std::set, std::map, std::unordered_map and std::unordered_set to C++14 users. That's a follow up to the previous post !

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Spectre is not a Bug, it is a Feature

What happens if one builds up on the Spectre vulnerability to implement a convoluted version of memcpy? From an obfuscator point-of-view, it unleashes a wide range of opportunities, which turn a definite bug into a fun[nk]y feature.

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Have fun with LIEF and Executable Formats

This blog post introduces new features of LIEF as well as some uses cases.

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Frozen - An header-only, constexpr alternative to gperf for C++14 users

An open source, header-only library that provides fast, immutable, constexpr-compatible implementation of std::set, std::map, std::unordered_map and std::unordered_set to C++14 users. It can be used as an alternative to gperf.

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LIEF - Library to Instrument Executable Formats

QuarksLab is open-sourcing LIEF, a library to parse and manipulate ELF, PE and Mach-O binary formats. This blog post explains the purpose of this project and some parts of its architecture.

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Global Dead Code Elimination for LLVM, revisited

While building an LLVM-based obfuscator, we explore some unexpected code areas. For instance, what happens when you try to optimize a single function that holds millions of instructions? Some LLVM passes start to suffer, including an unexpected one: Global Dead Code Elimination. Let's investigate!

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